Three Signs and Symptoms of a Blown Head Gasket

Updated on January 18, 2019
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Wrench Wench has been in love with automotive mechanics for decades. She loves sharing advice with fellow DIY mechs and curious cats.

Driver's Anxiety: Is My Head Gasket Blown?

Around the mid-section of your engine sits the cylinder head gasket, a vital element with the duty of keeping coolant and oil inside your engine and separate from each other. When this gasket fails, grim scenarios present themselves.

The best-case scenario, if you have been a super-vigilant driver, could be that you (or someone else) will have to remove everything above the cylinder head, to gain access to the head gasket so that it can be replaced. Though even if you have a mild head gasket problem like this, it's never just going to be the head gasket that gets replaced; any other gaskets or temperature-sensitive bolts will have to be replaced along the way.

A common worst-case scenario is that your head gasket broke slowly and has allowed coolant and oil to mix over time, tainting everything within the heart of your engine, which in order to function needs to remain a clean space always separate from all other engine fluids.

Because blown head gaskets often require such daunting work, most drivers end up ditching the engine and/or the entire car, just to avoid the hassle of DIY and the lofty prices common at modern mechanic shops.

If you recognize yourself in that last sentence, and you're worried your engine might have blown the head gasket, then you're in the right place!

Are you worried that your vehicle might have a bad head gasket?

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One of the most common signs you've got a blown head gasket: overheating
One of the most common signs you've got a blown head gasket: overheating | Source

Sign 1: Your Car Easily Overheats

Reoccurring engine overheating is one of the most common telltale signs that your engine has a faulty head gasket.

More specifically, your engine will overheat and bellow out white steam, regardless of whether or not you can see any leaking or spraying coolant. You will also likely notice a sickly-sweet smell (coolant), steam (hot water burning off), and wet oil, oil contaminated with water (you'd have to smell it to know what it smells like).

If your vehicle has started overheating and you cannot find another direct source of the overheating, then it is very likely you do have a bad head gasket. If you are still able to start and drive the vehicle from one point to the next, then you have not yet blown out the gasket bad enough to prevent operating it. Nevertheless, in this scenario you need to STOP driving the vehicle immediately and work to diagnose if the head gasket is failing.

If you've already gone beyond the point of no return, then there are only two paths forward: get rid of the car, or replace the cylinder head gasket along with anything else that might've been damaged along the way.

Common sign of a bad head gasket: Oil mixed with coolant in the radiator.
Common sign of a bad head gasket: Oil mixed with coolant in the radiator. | Source

Sign 2: Mixed Coolant and Oil

Considering that it's the head gasket's job to keep oil and coolant from mixing, one of the most obvious (and common) signs that your head gasket has failed is a noticeable mixture of oil in the coolant system, or coolant in the oil system.

The first place to check for this sign: the radiator.

If only mild mixing has occurred, you might only see a little bit of green, yellow, muddy or clay-colored liquid on the cap. If the leak has progressed far enough, your radiator coolant will look like the local coffee barista emptied an old latte into the tank.

Likewise, if coolant has gotten into the internal areas of the engine, then your oil cap or dipstick are going to have the milky coffee goo on them.

If you truly want to be sure, you can empty the oil and coolant from the engine and examine them, which will make clear whether your engine oil and coolant have mixed somewhere.


Sign 3: Car Won't Start

When your engine isn't starting because of a bad head gasket, you're going to notice certain symptoms:

  • The engine turns over but doesn't start
  • Each time the engine rotates, the battery dies more.
  • Even when the starter catches, the engine will not ignite.
  • The engine behaves as if it doesn't have enough fuel or spark.
  • The spark plugs test fine, yet the engine still behaves as if the plugs aren't firing.

These symptoms often occur because your fouled-up head gasket has created enough of an opening in the heart of the engine that it's no longer able to build up any compression, thereby preventing any spark or combustion.

Without diving blind into the middle of the engine, the only way to test for a compression leak is to use a compression tester; an ultra-simple diagnostic tool designed to tell you if your engine has enough compression to contribute to the boom/bust cycle required to power your modern combustion engine.

Time to dig out your Tools!
Time to dig out your Tools! | Source

Two Ways to Test a Head Gasket

Coolant Pressure Test

Performing a Coolant Pressure Test will help you determine if there are any holes in your coolant system. A positive test result does not mean you definitely have a bad head gasket, but a negative result suggests you don't.

Use the video below to learn how to perform the test.

Cylinder Compression Test

As with the coolant pressure test, if you do a cylinder compression test and it shows a loss of compression in the cylinders, that doesn't necessarily mean you have a bad head gasket, but if you do have a blown head gasket you will definitely see a loss of compression in the cylinders.

Compression Testers are a must have for all of you DIY mechanics. Being able to quickly test the compression of an engine that has trouble starting or idling can save you days of time in diagnosis.

Review: Signs of a Blown Head Gasket

Oil and Coolant Mixed
Engine Won't Start
No Compression
White Steam from Exhaust Pipes (While Running)
White Steam from Engine Compartment (while Overheating)
Driver andor Mechanic Anxiety
No Engine Compression
No Coolant System Pressure
Engine Turns Over but Won't Start
Signs of No Spark while Spark Plugs Operational
Battery Gets Tired Quickly w/each Rotation
Unexplained Coolant Loss

Do You Want to Replace Your Head Gasket Yourself?

A more complete text tutorial for how to access and replace a head gasket on various common vehicles, will appear on my articles list in the near future. Until then, there are plenty of fancy pants mechanics on YouTube who've already made super-easy tutorial videos to help you bold DIY'ers get through such a big job.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

© 2018 Wrench Wench


Submit a Comment
  • profile image

    Ken Barnett 

    20 months ago

    The surest way to tell if your head gasket is the problem, or at least if you have coolant in your oil. Is to unscrew your oil plug (under the car on the oil pan) just enough to get a small sample (about a cup full) and drip a little bit onto a hot skillet, if it sizzles and boils a bit you have coolant, if it just smokes up the kitchen (clean up the kitchen real quick and get out of there before your wife sees what you've been doing). You can eisily test this method by mixing a couple of drops of water into some 10-40 and drip it into a hot skillet, then try some clean 10-40 to see what you are looking for.


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