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Five Signs That Your Car Has a Bad Heater Core

Updated on February 17, 2017
Good old Toyota radiator
Good old Toyota radiator

Heater Core, O Heater Core ... Wherefore Art Thou, Heater Core?

You might be wondering what the heck a heater core is, what it does, and how it can affect your vehicle. These are all great questions, and we’re going to get you some quick and easy answers so you can get your car fixed ASAP.

What Is a Heater Core?

It’s part of the car’s cooling system. It looks exactly like the mini-me version of your radiator, and is, in fact, a small radiator itself, with a grid of little tubes and a waffled appearance from the fins that disperse the heat. Your heater core allows your heater and defroster to function.

What Does a Heater Core Do?

Your heater core circulates coolant through the little tubes; the coolant comes in through one heater hose and out the other, radiating heat into your cabin so you don’t freeze on those cold winter mornings. It's also responsible for allowing your defroster to function properly, and it's linked into the air conditioning system, which is organized around similar principles.

Where Is the Heater Core Located?

Your heater core is usually behind your dashboard, under the center or the passenger side. It will have some sort of casing or housing and is usually buried behind almost every other component of the dashboard.

How Do I Know If My Heater Core Has Gone Bad?

I'll give you five clues below that will help you decide. Diagnosing a bad or blown heater core is pretty easy. Replacing a heater core—maybe not so easy.

Toyota Supra heater core
Toyota Supra heater core | Source

Note to Readers!

You might experience only a few of these symptoms of a bad heater core, or you might experience all of them at once. A lot of this depends on your vehicle, it's age and the state of your vehicles health at the time when your core goes bad.

1. Is It Foggy In Here?

The most common tipoff to a problem with a heater core is when the inside of your car suddenly fogs up for no reason. And when I say "fogs up," I'm not talking about a little mist on the edge of the windshield, I'm saying every window is covered with moist, warm condensation.

What may have happened is that your heater core blew while you are driving, after the engine warmed up. The warm coolant leaking into the cabin of the vehicle caused fog because that coolant was previously sitting inside a warm and temperature-regulated coolant system, and now it's evaporating into steam as it hits the cooler air inside your car.

2. Do You Smell Melons?

Whether or not the car got all foggy when the heater core broke, an unmistakable sign of a leaking heater is a fruity, sickly-sweet smell inside the car. This is the smell of your radiator fluid and definitely a sign that coolant is leaking into your car.

You might also smell this lovely smell around the outside of your car, which means it's time to look underneath your vehicle and see how much of that coolant has spilled out onto the ground.

Look for leaks.
Look for leaks. | Source

3. Your Car Is Rather Thirsty

If you find your car, truck, or van has suddenly developed a voracious appetite for coolant, and you cannot figure out where it's all going, you may well be looking at a blown heater core. Sadly, if the leak is hard to find, the reason may be that the coolant has been leaking into your cabin when the system is cold, and instead of making fog it's creating a puddle. The first place I usually check to confirm a bad heater core is the passenger-side floor. If it is soaking wet, and so are any forgotten shoes or fast-food bags lying around down there, then I know to suspect the heater core.

Check the floor of the car for sogginess, especially near the front passenger seat.
Check the floor of the car for sogginess, especially near the front passenger seat. | Source

4. Brrr! It's Cold in Here!

A chilly passenger compartment is not always a sign of a faulty heater core. It may indicate that your blower motor or another component of your heater has gone bad (cheer up, it may be a component that’s less tedious to fix than the heater core). Though if you're seeing one of the other signs in additiion to a lack of heat, that's a pretty good indicator that the heater core itself has a problem.

When a hole or puncture develops in your heater core, all that warm air may escape too quickly to reach you at the other end of the heater ducts. Depending on the size of the puncture, you might feel mildly warm, lukewarm, or absolutely freezing air coming from your heater.

5. Cold Cabin, Hot Engine

If you find that your vehicle has overheated, or continues to overheat, you'll want to check on the health of your heater core for sure. Bear in mind though, that many other parts of the car could be involved in the overheating. If your heater stops putting out heat, and your engine seems warm, investigate whether there is a coolant leak elsewhere, or some other issue with your car.

Overheating is very serious for your car. All sorts of major components of your car will wear and break down in record speed when they get too hot. If your car overheats, investigate the problem and get it fixed ASAP. If the temperature gauge goes up into the danger zone, don’t drive it; tow it. You don't have to heed my words, but I can guarantee you'll learn a hard lesson if you don't.

If your car overheats, stop and think.
If your car overheats, stop and think. | Source

Signs of a Bad Heater Core

More Diagnosis: Testing the Pressure in the Cooling System

How Do You Change a Heater Core?

This job is way easier to describe than it is to perform. So, often a DIY'er will check out a Chilton's Manual or other auto guide and say, "No problem! I can change a heater core!"

I'm all for this kind of enthusiasm; it's how I myself got into changing heater cores. Though let me forewarn you that it is a very tedious task, and once you know how to do it, all your friends and family will want you to change theirs too!

With that warning out of the way, I'm only going to give you a very basic guide for most cars and trucks from 1958 to 2010. For the details for your particular vehicle, you'll need to do your own digging.

Does This Look Like Fun?

Heater core replacement on a Supra
Heater core replacement on a Supra | Source

Share Your Experience, Or Ask More Questions

I love to hear old heater core job stories. They can be epic battles, depending on what kind of vehicle we're talking about. If you leave me a question or a story in the comments below, please tell me the year, make and model of your vehicle.

How To Change a Heater Core

1. Disconnect the battery.
2. Remove the steering wheel from the vehicle.
3. Remove any outer doors or casings from things like the fuse box, speakers. and kick panels.
4. Remove the glove box, radio, speakers, and any accessories.
5. Remove any gauges (be careful if you have a speedometer cable back there!).
6. Detach and remove your heater and air conditioner controls.
7. Unbolt and remove the dashboard.
8. Do not disconnect your air conditioning unless it's absolutely necessary and only if you have the proper means to dispose of the Freon. Do not just let it leak into the air. It is bad for the ozone layer and is toxic, especially to people with heart conditions.
9. Disconnect the two heater hoses from the engine compartment.
10. Move any air ducts or other components away from the heater core housing.
11. Remove the heater core housing and set it on a table. Remove any screws or fasteners to gain access to the heater core.
12. Take the old core out and put a new one in!

To install your heater core, just follow these instructions in reverse. If anything got broken on the way out, please make sure to replace it on the way in.

CAUTION:

As with most DIY tasks, you take on this one along with all the risks involved. These instructions are very basic and meant for a person who is already very mechanically inclined. If you don't have appropriate tools, safety knowledge, and a strong mechanical aptitude, you'll want to seriously consider taking your vehicle to a garage to be fixed by a professional.

You're looking for answers, and I'm looking to give you answers! So, you ask them in the comment section below, and I will answer them as quickly and as accurately as I can. Please keep in mind that the more details you can provide about your car and your problem, the better quality advice I can give you.

Also, if you're question is not answered in this article, please check my other articles, as I might just have created a whole new hub with your question in mind!

Questions and Answers!

Question: Is it Possible to Have a Broken Heater Core and NOT Exhibit Each of the Signs?

I own a 2005 Honda Civic. Lately, my a/c has been on and off running Lukewarm and as I gain speed, getting colder. My passenger side floor HAS been thoroughly soaked but not recently. However, I have not had any problems with coolant being low. No overheating. I'm certainly NOT a mechanic...I'm a female. I get in and drive. If it needs gas I fill it up. If it needs oil I get it changed....that sums it up.

Is it possible to have a broken heater core and NOT exhibit each of the signs?

Answer: Yes! It's Definitely Possible

There are plenty of times when heater cores will go bottom up, and only barely exhibit one or two symptoms. In 90% of cases, you're going to clearly experience at least two or three signs that give away the culprit.

In you're particular situation, especially without any loss of coolant, while I wouldn't rule out a bad heater core, I would look first towards your air conditioning unit. While it's not unusual for an aging vehicle to take a little time to blow out crisp and cold air, if your a/c is on the fritz, it could also be the culprit soaking your passenger side floor. Alternatively, you could also have a leak in the seals around your door, windshield or firewall -- all of which could be soaking the floor as well.

Question: Still Smelling Coolant, Is This Normal?

Just bought a 2008 Chevy equinox. That same day I could smell antifreeze while the heat was running. So I took it right back and they said bad heater core. I got it back today, heat works great! But...I can still smell a very slight scent of antifreeze. Not like before and it even seems to lessen as I drive. But when I restart it I smell it again slightly. Could this just be normal after having one fixed, maybe there's a residue in the vents or something? I'm hoping it just goes away after a day or so. Opinion?

Answer: Yes... and No...

To answer your question in general, Yes -- it's not unusual to smell a bit of residual coolant drying up in the system.

That being said, it's not normal if this smell persists for more than a few days of driving. So, in greater detail to your individual plight, since you are describing a chronic type persistence in this smell, I would urge you to take your chevy back to the mechanic and have them check for any small leaks if your coolant system. While it could just be some residual coolant, it's more likely that there is a small leak somewhere that wasn't caught originally, or that occurred after your last heater core was replaced. It's not unheard of for this to happen, especially if your vehicle experienced an overheat or any serious pressure in the coolant system when the heater core went bad.

Question: How Much Does Repair of the Heater Core Cost?

I am positive I have a heater core problem. Ironically, it started the day I got my car back from getting a fuel pump relay repaired. After paying a lot for the fuel pump relay, how much does repair of the heater core cost?

Answer: The Ballpark Price of Heater Core Replacement

This is a difficult question to answer, only because it depends on what country and/or state you live in, what type of mechanic you see and what type of vehicle you drive.

That being said, I can offer a ballpark idea of what I might charge and what common prices are found in my area (Seattle, Wa).

For me, a heater core is often a large job, not because it's difficult, but because in nearly all vehicles, the heater core is behind the dashboard. So unless I have direct experience with a particular year, make and model that I've performed this on, my initial assumption is that it will take no less than 8 hours to disassemble the dashboard, retrieve and replace the heater core and then reassemble the dash around it again. This is a general time estimate, including most newer cars that usually have lots of delicate electrical elements, clips and knucklebangers. As a mobile mechanic, my usual going labor rate was $60 an hour. So a general estimate for a heater core would be around $480.

Now, shops in the area, who often have more specialized tools, lifts and predictable work environments, can often get the job done in half the time. Though because they are running a business, they're shop rates are going to be higher -- $90 to $150 average. So for a 4-6 hour job in a shop, you're looking at a minimum of $360 to $600, plus the price of their preferred manufacturers heater core.

Question: Where's That Leak Coming From?

I own a 96 chevy corsica 4 cylinder. 2 days ago, on my way back from work, I smelled a very sweet humid icky smell (coolant) inside my car. I kept driving only to see that white smoke started coming from my vents and my car started rapidly overheating. I pulled over to let the car cool about 6 times on the way home. When I got home, I looked under the hood and seen alllll of my coolant was gone after just getting it filled 2 weeks earlier. I asked around and everyone kept telling me HEATER CORE HEATER CORE HEATER CORE. But everyone also kept telling me to look for the missing coolant on ypur passenger side floor. Its STILL DRY. I jacked up my car to find a leak and poured a gallon of water into the coolant compartment to do just that and quickly jumped under the car. But what I found was all of the water was pouring out thru a 1 inch pipe connected tp absolutely nothing right underneath the heater core. No leakage from actual core itself. I was wondering if you could tell me if that is still a heater core problem or something else before I start tearing my dash apart? Please and thank you. :)

Answer: Pipes to Nowhere...

Okay, I first have to thank you for sharing this complication. To tell you the truth, without being able to stick my head under your hood, it's a little bit difficult to narrow down what you're seeing precisely. That being said, from your information, I would suggest that it's likely that your disconnected 'pipe' either used to be connected to your heater core as a part of the inlet hose.

Your heater core is a really basic set up. You have your main radiator in the front of the car and two hoses (it's not often that they are pipes, but it's not unheard of), an inlet and an outlet, that connect to the corresponding pipes attached to the heater core. These pipes will often protrude from the fire wall, which is where I suspect you're seeing this "pipe to nowhere".

Question: Symptoms Before the Heater Core Goes Bad?

My mom's car just got repaired because of either the radiator or the fan kept turning off. But now every time we turn the heater on in the car, it will be warm, but I can smell something sweet, like syrup almost. I was worried about it, but someone told me that it wasn't the heater core because it won't give you any warning before it damages and that the mechanics probably just accidentally spilled some antifreeze. I really don't know what to think.

Answer: Bye Bye Heater Core...

I have to say, while I'm sure they meant well, it's sure naughty of your friends to assume that a+b always equals c, when it comes to cars. I'm no master mechanic, but out of everything I've learned, and that all other mechanics I know have learned, it's that vehicles don't always act the way they are supposed to. In fact, I'd imagine that 90% of professional repairs could be handled by any old monkey with a wrench, if it weren't for the fact that cars and trucks are like 5 year olds. Sometimes they are straight up text book, sometimes they do something completely bizarre and unexplainable, and you find out that it's something super easy and right in front of your face.

When it comes to heater cores, it's extremely common for them to leak out into your passenger compartment, because they are usually right up underneath the dashboard inside your car. Though the leak could be from somewhere else, such as the inlet or outlet hoses, where they would spill out onto the ground. If that happened, you wouldn't have your passenger floor soaked.

The same thing could be said about heater core's just "dying" without any warning. That is very common, though it's not because they're aren't any signs before hand, it's because most of us are too busy driving to notice the signs unless they stick out. So smelling coolant, could definitely be a sign that your heater core has a slow leak and may need to be replaced soon. That being said, it doesn't mean that it is your heater core. If it were me, I would use a coolant leak checking tool, or take it to a shop and have them use one. In the first day or two after having a radiator changed, it would be expected to smell a little bit of drying coolant, but a chronic smell every time you turn the heater on, shows there is definitely something worth checking out; before something just dies on you without warning.

Question: Foggy Windows

I have an '01 Malibu. I've replaced the thermostat and the heater core thinking that would stop my car windows from fogging up but even after those repairs my windows are still fogging up.... What's wrong?

Answer: Check Things Out

Without knowing more, my initial suggestion would be to have your new heater core and thermostat checked out. In this instance, it would more likely be a faulty thermostat than a faulty heater core, though you won't know until you have them checked.

That being said, before going too much further, I would also check out the seals around your windows. It could be as simple as a seal leak that is allowing moisture into your car and preventing them from completely defrosting.

Comments

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    • profile image

      Addye 2 years ago

      I own a 2005 Honda Civic. Lately, my a/c has been on and off running Lukewarm and as I gain speed, getting colder. My passenger side floor HAS been thoroughly soaked but not recently. However, I have not had any problems with coolant being low. No overheating. I'm certainly NOT a mechanic...I'm a female. I get in and drive. If it needs gas I fill it up. If it needs oil I get it changed....that sums it up.

      Is it possible to have a broken heater core and NOT exhibit each of the signs?

    • Nicole Stanley profile image

      Nicole Stanley 2 years ago from Victoria Australia

      Nice post. A good car owner must understand his responsibility to properly maintain their car. Checking the car on regular basis is important as we get to know that all the parts are running properly or not.

      Mechanic Glen Waverley

    • profile image

      Shannon Shipp 2 years ago

      Just bought a 2008 Chevy equinox. That same day I could smell antifreeze while tag heat was running. So I took it right back and they said bad heater core. I got it back today, heat works great! But...I can still smell a very slight scent of antifreeze. Not like before and it even seems to lessen as I drive. But when I restart it I smell it again slightly. Could this just be normal after having one fixed, maybe there's a residue in the vents or something? I'm hoping it just goes away after a day or so. Opinion?

    • profile image

      Tonya 2 years ago

      Why is my car blowing heat on drivers side only.... It's the duel kind of control

    • profile image

      Liz 2 years ago

      I am positive I have a heater core problem. Ironically, I started the day I got my car back from getting a fuel pump relay repaired. After paying a lot for the fuel pump relay, how much does repair of the heater core cost?

    • profile image

      teddy 2 years ago

      I own a 96 chevy corsica 4 cylinder. 2 days ago, on my way back from work, I smelled a very sweet humid icky smell (coolant) inside my car. I kept driving only to see that white smoke started coming from my vents and my car started rapidly overheating. I pulled over to let the car cool about 6 times on the way home. When I got home, I looked under the hood and seen alllll of my coolant was gone after just getting it filled 2 weeks earlier. I asked around and everyone kept telling me HEATER CORE HEATER CORE HEATER CORE. But everyone also kept telling me to look for the missing coolant on ypur passenger side floor. Its STILL DRY. I jacked up my car to find a leak and poured a gallon of water into the coolant compartment to do just that and quickly jumped under the car. But what I found was all of the water was pouring out thru a 1 inch pipe connected tp absolutely nothing right underneath the heater core. No leakage from actual core itself. I was wondering if you could tell me if that is still a heater core problem or something else before I start tearing my dash apart? Please and thank you. :)

    • profile image

      Kimberly 2 years ago

      My mom's car just got repaired because of either the radiator or the fan kept turning off. But now every time we turn the heater on in the car, it will be warm, but I can smell something sweet, like syrup almost. I was worried about it, but someone told me that it wasn't the heater core because it won't give you any warning before it damages and that the mechanics probably just accidentally spilled some antifreeze. I really don't know what to think.

    • Stephanie Robuste profile image

      Stephanie Robuste 2 years ago

      I have an 01 Malibu I've replaced the thermostat and the heater core thinking that would stop my car windows from fogging up but even after those repairs my windows are still fogging up.... What's wrong?

    • profile image

      Roger 2 years ago

      Why is my car getting a little hot and blowing cold air I changed the water pump, thermostat,radiator and belt but nothing has changed it's an 2002 grand-am gt 3400 V-6

    • profile image

      Hilary 2 years ago

      2002 Chevy Blazer was told it heater core windows fog terrivbly and smoly fumes come through vents but heater still works very well

    • profile image

      2 years ago

      great article. nice simple language, easy instructions. Still gonna pay someone to do it but was wondering if I should get my own heater core. the shop wants 700 bucks and I can get one for 60 online. is there a difference between theirs and one from autoparts warehouse? 03 Jeep Liberty Sport 6cyl3.7 ltr

      thanks

    • profile image

      doris 2 years ago

      1995 Chevy blazer 4x4. I've had no indications of cold are or leaks. Mech took hoses off and told Me radiator is blocked and I need heater core after putting in new radiator. If left like this it would mess radiator again.

    • MikeNV profile image

      MikeNV 2 years ago from Henderson, NV

      I personally wouldn't thing Heather Core until now thank you. I'd think Radiator or Water Pump or something else. Found coolant on the garage floor and it turned out to be leading Manifold Gaskets. Interesting to not that the smell could be related. Enjoyed the Read.

    • profile image

      Lori 2 years ago

      The fan on my 05 Jeep Grand Cherokee Larado would only blow on high, so the Jeep Dealership replaced the resistor - blower motor. It worked fine one all 4 speeds. Two days later, I accidentally bumped on the a/c. When I turned it off, there was no heat. It only blew cold air. The mechanic says I need to replace the heater core and that it's not related to the work they did. What are your thoughts?

    • profile image

      alex19760328 2 years ago

      Enjoyed the Read thx

    • profile image

      theresa 2 years ago

      My 2011 jeep grand Cherokee puts out heat on the passenger side all the time. Everything on the drivers side works fine. Also the blower motor will just shut off for no apparent reason. Dealer is telling me it's the heater core. I antifreeze smell or foginess. Please help. They want a f I r tune for the part and 6 hrs labor. Am I getting taken cuz I m a woman?

    • profile image

      theresa 2 years ago

      Wrong sentence. I meant to say I do not smell antifreeze,have wet carpet or foginess.

    • profile image

      Sharon 2 years ago

      I have water dripping from under my dash except it's not hot it's very cold and there's no fog or anything like you described,do you have any idea what might be wrong please help

    • profile image

      linda 2 years ago

      I have a 2007 ford taurus do a heater core stop a air condition from working

    • profile image

      Nay Valitio 2 years ago from Orlando, FL

      Seen this thread & wanted to add, plus ask question. Per my Dodge Ram 1998 Chilton book it says if steam on windows fogging occurs but it's cool check hoses for being clogged (clean them). Took truck to 4 mechanics all said just change the core, no one wanted to even listen to me or believe me even when showing them the book. Passenger floor not wet, no smell, just fogging up, still had heat and good heat. Only thing was turning it on sometimes the windows would get like a shower and the steam, fog would come out like a fire was going on my truck. This was pretty bad considering had moved to GA right before it snowed 2013 and GA shut itself down. Well I personally replaced the compressor A/C (easier than I thought) and nice cold air but 1st day in use after recharging and evacuate done it soaked the floor on passenger side. Now I still have heat, still get cold air checked coolant but not low. Prior to compressor it was sucking coolant but floor was not wet, never saw coolant on ground, but a wet substance certainly not green. I added Best Line product to radiator (not even 1/4 of bottle) prior to leaving GA back to FL and no signs of fluid being low. Checked noticed passenger side not wet. Question: if hoses are clogged and it's not circulating like it's supposed to wouldn't that keep the radiator level consistent but near heater core low which would mean it's trying to pull or suck fluid through but there is nothing there? And can I perform a hose flush myself? Since I can't get a mechanic to do it I'll perform myself. Thank you.

    • profile image

      jenn 2 years ago

      I have a 94 ford flair side and I smell a sweet small inside of my truck and my windows will fog up what does that mean

    • profile image

      boscho 2 years ago

      my damn ford 150 is a bitch. my window fog n it runs hot. i go to crank it up it dont even stsrt now

    • profile image

      herndog58 2 years ago

      Where do I find the answers to these comments?

      Specifically to teddy 7 months ago?

    • profile image

      Terry 22 months ago

      I have a 2001 chevy silverado 1500 4.8 liter...I'm thinking my heater core has a hole in it for sure. The passenger floorboard is soaked n smells like coolant and when I park the truck and turn the engine off it comes out pretty good from underneath as well. This doesn't look like a fun job no matter the make or model!! Any tips to make it easier along the way??

    • profile image

      Jason. lucidspider69@yahoo 21 months ago

      So my coolant has a leak and i could fill the coolant get pressure and drive it without overheating. However i tried bars stop leak in it. And something happened when i drove ot last. The engine over heater and smke started pouring out of my heat vents and hood. What is wrong with it is it a heater core. Head gasket. Or?... please let me know what u rhink and rhe smoke smelt bitter

    • profile image

      Margaret 20 months ago

      We have a Ford Focus 08 every time you turn on the heater or air conditioner it smells like rubber then it kinda goes away, any idea what it could be.

    • profile image

      Samantha 20 months ago

      My husband (who is a diesel tech) replaced a corroded hose coming from my heater core that had a pin hole in it. We thought that might fix the problem of no heat in my van but there's still no heat. The windows don't fog up, my floor is not wet, and I don't smell anything sweet in the van but when I turn on the heat there is a loud whistle like sound that won't go away for a while when it's turned on. Could this be the blower motor going out? If we replace that will I have heat in my van again?? it's getting too cold out to have my babies in my van with no heat.

    • profile image

      Jason 20 months ago

      I feel sorry for anyone who has to do this crappy task. After varifying that the ac/heater controls were all working and the acuator door was functioning and the blower motor was working I was left with no option but to swap the heater core in my 03 sonoma 4.3L step side.

      My only benifit is that I build custom cars so I have a full shop and heated garage ,but for the average DIY guy with a handful of tools you use for oil changes and plug changes I would not recommend this as a home project. I have seen many people come into my garage with there ride on a tow truck because they can't get the dash back in or worse yet they didn't disconnect the battery and managed to set off an airbag ripped the wiring harness ect ect.

      If you can't afford to take this to a shop where most likely the bill is going to be close to over a $1000 look in your local classifieds for someone who can do the job for you that has the skill set who can do the job. There is always guys like me out there who are willing to do these nasty jobs for a decent price and like myself most are gearheads who hold a class A licience in automotive repair.

    • profile image

      william 18 months ago

      Question ; 2002 trailblazer has antifreeze on DRIVER SIDE floor. Is it more than likely my heater core? I noticed it after my buddy installed a new stereo???

    • WrenchWench profile image
      Author

      Wrench Wench 18 months ago from Seattle

      I haven't had a moment to look up that model, but in many vehicles, the heater core is more towards the center of the car, instead of being right above the passenger side floor. When they're more in the center, there's greater potential for coolant to spill onto the drivers side floor. I remember the first truck I went to work on that had the exact same problem; coolant soaking onto the drivers side floor. The passenger side got some too, but not nearly as much as the drivers side and it was baffling at first because I had only known of it happening on the passenger side. Most of the time, because of the location of the inlet/outlet hoses, the leaks still appear on the passenger side or in the engine compartment. Though the only thing I could think of was that had to be the heater core, as there really was no other reason for coolant to be coming into the cab of the truck. The rest of the coolant system is all in the engine compartment.

      So I tore out the dash, removed the heater core and ran a crap ton of water through it and found it had been leaking through one of the bottom welds that had separated over time.

      The only way to really double check this theory, is to drain your radiator and then stick a hose in it and let it fill up and over run. Then go inside your trailblazer and stick your hand up behind the center console (Where the radio and such is) and wait to see if you feel any water coming through. It might squirt a little or a lot, or you might just notice the carpet getting wetter. If the leak is small, it could take a while to notice anything or you might not notice anything at all. Doesn't mean it's not the heater core, but that's the only way I can think of without specialty tools, to check the core before removing it.

      As far as any of this having to do with the stereo your buddy installed, it's highly unlikely it had anything to do with your heater core leak unless your friend is uniquely talented and somehow decided to stick a stray screw deep into your center console and somehow got it right into the coils of the core. Though that was be some AMAZING talent, lol

    • profile image

      Elaine 18 months ago

      My heater was working fine earlier and i went out but no heat or air coming through the vents i have a 94 suzuki sidekick, any suggestions

    • WrenchWench profile image
      Author

      Wrench Wench 18 months ago from Seattle

      Elaine, thank for your question. First, I would check or have your Blower Motor checked. Usually if it's a heater core, you'll still air, it just won't warm up. If you're getting at all, my first thought would the blower motor.

    • craftybegonia profile image

      craftybegonia 18 months ago from Southwestern, United States

      This is very useful information, especially for those of us who are really ignorant when it comes to auto mechanics. Thanks for sharing!

    • robhampton profile image

      Rob Hampton 18 months ago from Tampa Bay, Florida

      I think I am just going to bypass the heater core.

    • WrenchWench profile image
      Author

      Wrench Wench 18 months ago from Seattle

      Bypassing the heater core is an interesting choice. I hope you don't intend on driving your car in the winter, lol

    • profile image

      pam 17 months ago

      It's ok to bypass it, right?

    • profile image

      Pam 17 months ago

      I live in Arizona. I haven't used the heater in years.

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      kevin 17 months ago

      I have a 2000 f250 and no heat I have changed everything and now I am looking at the heater core it is hot on the top and bottom but in the little fan that blows cold air right through

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      Bigbremac@yahoo.com 17 months ago

      Heater core has been bypassed in the past in a 87 Lincoln Continental. Just bought the vehicle in New England where it is very cold and I was told the vehicle had only been driven in the warm weather before. I am wondering some safe ways to test the current heater core that's in place such as trying to run water through it but running the risk of getting water on electronics in the dash area. I am also seeking a safe way to open the bypass connected to the radiator hoses to test and hopefully connect the hoses to the heater core and test after connection. Sorry ahead of time if this is too much. Included my email in case I don't see this.

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      Robert Collins 16 months ago

      Completely confused. I have a 2012 Mazda 3. We have a couple signs that there might be a bad heater core,but the water we have is in the back only. there is zero water in the front passenger floorboard. we don't have the sweet smell, but when we turn on the air it takes awhile if at all for the AC to work. At first we thought that maybe there was a leak from the sunroof as the water only appeared after a rain or car wash. Not I just don't know. I don,t want to dish out $1,500.00 for a heater core and then find that's not the problem. Do you have any comments that the sun roof may be leaking or can this water problem be from some other source?

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      Wrench Wench 16 months ago from Seattle

      @Robert Collins, yes there are certainly other things it could be, and your smart to check them all before shelling out the big bucks for a new heater core, especially since you are getting water in the back of the car and not the front, which is not where any of your heater core components are located and not likely to be the heater core at all. With the info you've given me, I would first check:

      -The seal around the sunroof - you can easily check this by having someone sit inside the car while someone else sprays a hose on top of the car. Just watch and wait. If there's a leak, you'll see it.

      -The sunroof latch (make sure it latches firmly)

      - The Sunroof Drain Tube - In your model of car, these drains "should" be underneath the rear plastic sill plates or "runners" that are screwed into the frame of the car. You'll see them when the door is open. Unscrew them and gently remove the runners, then look for a little plastic tube. It will probably be white or gray. The tube "should" run off into an outlet hole with or without a "port". These annoying little tubes tend to get clogged and then they backup and start draining inside the car. You would think the owners manual or the car makers would warn people, but they don't. If you can find it, push some air through them with an air compressor. Even a little air compressor might only run you around $40 bucks, which is way better than $1500 and you'll need it to clean the tubes again if this is your current problem.

      You could also try doing what the guy in this video does, though you might need to remove any "ports" or filters they've placed on the end of the drain tube, in order to get the crud out of there.

      If you still haven't found the leak, check:

      -The seals around all doors (Use the hose again)

      -The welds underneath the headliner (the fabric on the ceiling of the car) closest to the doors (Use the hose again)

      -The floorboards under the front seats. You'll have to pull up the carpet to check the floor boards.

      -The seals around the rear windshield (get the hose again)

      If you don't find the culprit from any of these places, a great way to check and see if it really is your heater core, is to drain all the coolant from your system, then put a hose into the radiator and let it run. Let it over fill and keep going. Get into the car and wait to see if you get water inside the car. Again, this almost always happens in the front, usually on the passenger side floor, but if your car is just bizarre, you'll see water coming in from running the hose in there.

      Good luck and let me know when you find the source of the leak!

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      Mary 15 months ago

      If my radiator is broken and I need a new heater core...which one should I fix first?

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      Alexander Silvius 15 months ago from beautiful, rainy, green Portland, Oregon

      That kind of confirmed it for me, thanks! I also appreciate the round about price guess you offered, it gives me something to work with as I add up the expenses for my beautiful beast. I love my old wagon and she has been reliable all the years I have had her. It needs a lot of maintenance, but I think it's still cheaper than a car payment. I probably spend an average of 2000 a year on her, sometimes less if I put things off.

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      Pam 15 months ago

      2002 jeep liberty sport, flushed heater, new radiated, new thermostat, cabin heat only heats to 60 to 80. Why isn't it heating properly?

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      ydroza 13 months ago

      I had to get my radiator replaced in Jan 2016 as my Jeep Wrangler '07 started guzzling coolant. $4000 later, when I got my jeep back I noticed a strong smell of coolant inside the car and the windshield misting over.

      Called the mechanics once again and was advised that told the there was a leak from the water pump. Nothing to do with the previous issue of radiator leaking. Paid another $700.

      A week later called the mechanics again because the windshield was still misting over and there was smell of sickly sweet coolant inside the jeep. They put it under stress test and told me that there was nothing wrong.

      Now 5 months later having driven with the sickly sweet smell of coolant all through I feel that the mechanics have been shoddy but I'm not technical enough to have an argument with them and I am loath to part with another 1000$.

      Just wanted to check if this would have been an issue that the mechanics should have discovered when they initially repaired my vehicle or can they keep telling me that it's not related and I have to pay again?

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      dominic 13 months ago

      Eyes burning nose stopped up all the time and I always smell like something burning in .y freightliner coming threw vents

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      mike 11 months ago

      have 2004 cavilier water coming out of lower heater if bad heater core would smell antifreezze drain works what elso could it be?

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      Jay Avila 11 months ago

      If one of the hoses going into the heater core leaks, does that mean the core is going bad or just a simple leak. Want to avoid all that work of replacing the core if i don't have to.

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      Kris 11 months ago

      I own a 1995 Toyota T100 and my problem Started as leak by my evaporator core then a few days pass and I'm sitting a red light and I notice that my AC is blowing a thick fog out my two center vents I'm almost positive now that it's the heater core

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      Charlotte 10 months ago

      I'd like to know how long or should you drive a car IF you know or think it's a heater core you need.. I DO have a sweet white smoke from My vents.

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      Elvis mcgilvray 9 months ago

      On 2000 taurus it has a bypass line off. Top htr core line with it clamped off could it affair with trans.lines overheting.

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      Brandon Myers 8 months ago

      I have a 1976 ford granada and I noticed I have a hosee coming for the inside of the car threw the firewall. Is that the reason I could not be getting head inside the car

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      David 8 months ago

      I have a El Camino 85 heater core is in engine compartment how do I replace

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      Jason 7 months ago

      Got a 2011 Nissan Frontier with 64,000 miles on it. The truck will blow hot air running down the road with the heater going, but when I come to a complete stop it will start blowing cool air while the heater is still on. I don't feel that it is a blown heater core, I haven't seen any leaks, don't have any foggy windows when I turn the heater on, nor do I have any odors coming from my truck. I think it's just a clogged system. Can anyone clarify

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      Trevor 7 months ago

      Thanks for your expertise. I have an 05 Tahoe, first I'm not seeing none of the signs except my front heater is not working. My fan works great, as does my rear heat, but my front heat worked sporadically and now has since stopped working. Before I pour money into getting my heater core changed, could it be something else? Thank you

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      Michele 7 months ago

      Took out Ac pump cuz it didn't work now I have no heat.Any idea

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      Debbie 6 months ago

      Had a new heater core last winter had no heat coming from defrosted or upper heat vents. Was not hot air only lukewarm today I started my jeep liberty 2012 and heard a loud cracking noise and then there was no heat coming out of top passenger heat vent all others are working and air is still very hot. Can an actuator do that? Can a heater core block just one vent?

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      Kay 6 months ago

      I have a 1989 Chevy caprice and it's giving to much gas if I'm driving and tries to stop it wouldn't I'll have to put it in park and turn it off .. what can be the problem??? Please

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      FrankB 6 months ago

      Car was running hot with no heat.After new water pump and thermostat same resut.Could heater core cause overheating.Its almost as if theres no circulation

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      mary duane 6 months ago

      2006 dodge charger, heater works great but powdery smell comes out of every heat option except the one that blows heat on top and bottom.

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      martin 6 months ago

      Is it possible to skip heater core??

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      Linda 6 months ago

      I have a 2008 jeep patriot,my heat works fine and my temperature gauge is normal,but this morning it looked like maybe steam coming from under my hood,and my coolant level is fine,which does that mean?

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      Teresa 5 months ago

      I have a 98 chevy cavilier the heater core went out on it so we bypassed it for now but now my car will not start could the heater core stop it from starting up it will turn over just not start

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      Alfred 5 months ago

      I have a 05 Ford Mustang v6. I have had leaks in the passenger seat, freezing on cold days.. heater doesn't get hot, coolant leaks out every other week... so I'm pretty sure it's the heater core. In need of a step by step to completing this job..

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      James Salley 4 months ago

      I have a 2011 bmw 328i I was told heater core was clogg up but heat comes out good on driver side cold air on passenger side. Dose not lose antifreeze no smell dose not leak on floor dose not steen up windows how can it be heater core ???

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      Anthony 2 months ago

      I own a 2011 Chevy Aveo LT. I recently had the radiator replaced due to a leaky hose and crack but a few weeks later I noticed the cabin smelling like a minty sweet aroma and its only when the car isn't moving.

      I checked for leaks, wet/soaked floor boards, overheating, etc and so far nothing. It drives just fine also, so any help you can give me will be greatly appreciated.

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      johnny 2 months ago

      hey, heater core OR thermostat, 1998 4 door sedan base model cavalier, 2.2 l engine - overheating, coolant disappearing, within 15 minutes engine redlining, can sometimes hear gurgling noise coming from somewhere inside or under dash(?), when heat is turned off. sometimes temperature fluctuating on gauge, other times right up on bust! heater core was never change. Need replacement??

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      Isaiah Cope 2 months ago

      Stephanie Robuste: Hi, Im Isaiah. I have an 01 s10 pickup truck and my windows fog up also. My AC just went out in August and it was my compressor. My heater core just went out last night on my way home from school. I attend the Automotive Technology Center in Troutman Nc. I have seen this before a bunch and I believe I can diagnose this for you. I think that you have a vent that wont open or close causing it to either to stay open all the time or closed all the time. If your ac is bad it may cause fog cause the defroster isnt working. If nothing works, you may have a leak somewhere, you can tell if you smell coolant inside the car. I suggest using Rain x wipes and Rain x widow cleaner with the no fog stuff. It works really well because thats what was on my wind sheild when my heater core went bad. Maybe the car is really humid on the inside for some reason. I just want you to know that i am not ASE certified yet but i am working on it. I just enjoy helping others who need help. I hope it works. Good luck.

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      Dan 5 weeks ago

      Ok. I have a 2003 Envoy XL. I haven't noticed any of the typical signs of heater core issues. I noticed antifreeze coming out just in front of my driver door. I looked everywhere and saw no leaks. Checked water pump, resiorvior, anywhere I could think of. There's a set of lines going to the rear A/C running through there but that looks fine. The antifreeze appears to be draining down the chasis. I don't want to take everything apart just to check the heater core and it not be. Any ideas?

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