Hardlymoving writes about do-it-yourself automobile maintenance on various makes and models.
I. Replacing the Thermostat
On rare occasions, in high-mileage Camrys, the cooling system's thermostat may fail. A thermostat may lock up in either the open or closed position resulting in overcooling or overheating.
In one case when a thermostat failed, the customer complained that he was getting heat in the cabin. He said the temperature gauge on the dashboard would rise to the normal operating range during warmup, then rapidly move down to the cold range. I concluded this particular malfunction was due to a defective thermostat that would stick in the fully open position after reaching normal operating temperatures (around 190 degrees Fahrenheit). The only material cost of repairing this problem was $5 for a new thermostat and $8 for a gallon of new pre-mixed coolant. The customer had previously been quoted a sizable repair estimate, involving flushing the cooling system and installing a new heater core with new hoses.
Thermostat Replacement Procedure
1. First, make sure the engine is cool.
Then relieve any residual pressure in the cooling system by removing the radiator cap. Remove the lower radiator hose from the thermostat housing. This step may not be necessary if you feel you can remove the thermostat housing from the water pump by bending the hose.
2. Apply penetrating oil on the threads of the thermostat housing.
3. Use a 10 mm socket attached to a extension to remove the top nut from the housing stud.
Use no extension for the lower nut. A 10 mm box wrench can be used on the top nut, but there is very little twisting room for the lower nut unless the oil filter is removed.
4. Remove the thermostat housing with a strong tugging or pulling motion.
Approximately 1/2 gallon of coolant will leak out when the housing is removed. The thermostat will most likely be stuck inside the housing.
5. Remove the old thermostat with the attached rubber O-ring.
Transfer the O-ring to the new thermostat or use a new O-ring if you want.
6. Reverse the above steps for installation, refill the radiator with new fluid, start engine until warmed up and recheck fluid levels after cool down.
Allowing the engine to idle for 1/2 hour with the radiator cap off can help remove air pockets.
2. Replacing the Temperature Sensor
If the car continues to overheat even after installing a new thermostat, the problem could be caused by either a defective temperature sensor or a defective fan motor. Replacement of the water temperature sensor may be in order. This sensor is located on the bottom of the radiator opposite the coolant drain port. It works in conjunction with your car's ECU (Electronic Control Unit) to adjust the air/fuel mixture based on the coolant temperature. If the sensor is not sending the correct electrical signal, the ECU will misinterpret the signal by making the air/fuel mixture too rich or too lean. Most commonly, a malfunction of this sensor results in over-enriching the air/fuel mixture, causing the engine to stall at traffic stops. And an engine will run cooler with an enriched air/fuel mixture.
Temperature Sensor Replacement Procedure
This sensor has an O-ring, so ask for the O-ring when you buy a new sensor.
The easiest method of getting to and replacing the temperature sensor is by removing the passenger-side fan shroud assembly.
1. Disconnect the fan motor electrical connector.
2. Remove the two 10 mm shroud bolts that secure the shroud to the radiator.
3. Lift out the shroud from the lower radiator shroud sockets. The fan motor can be tested by applying 12 volts to the motor connector leads.
4. The temperature sensor is now exposed. Detach the electrical connector.
5. Use an open-end or box wrench to spin off the sensor. Once the sensor is removed, coolant will start leaking out. To keep all the coolant from draining out, quickly screw in the new sensor by hand. Don't forget the O-ring attached to the sensor.
6. Reverse the above steps for re-assembly, and replenish the leaked-out coolant. I recommend using only genuine Toyota coolant.
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.
Questions & Answers
Question: If I remove the oil filter, doesn't the oil pour out?
Answer: Usually yes unless you wait around a hour to let the oil in the filter drain out into the oil pan.
Question: Is replacing a thermostat a big job?
Answer: It is very simple. There's only two 10 mm nuts that hold the thermostat housing (which contains the thermostat). Those nuts are easy to remove if you remove the oil filter first.
Question: Is replacing the thermostat a big job?
Answer: There are only two 10 mm nuts that hold the thermostat housing (which contains the thermostat). Those nuts are easy to remove if you remove the oil filter first.
Del on October 22, 2017:
I have a 2000 corolla ce. Both fans on when supplied power. Replaced sensor by thermostat, replaced fan switch in fuse box, still same problem. Any thoughts. It runs fine, no dash lights etc... Just needs to be fixed. Thanks
Tosin on January 22, 2017:
I have a 1997 model Camry, of a recent a experience hard start (long start, about three rolling) before it will answer me. What could be the cause?
hardlymoving (author) from Memphis, TN on January 16, 2017:
Start by replacing the thermostat.
KK on January 15, 2017:
I have 1999 Toyota Camry LE 2.2 L, when I drive its temperature sensor gauge in car shows at C or close to C. Car heats up and show at 1/6 of range on needle above C at idle after drive (gauge moves). What should be course of action? Is it ok to drive?
Jei on December 26, 2016:
I have a 2001 Camry in Cancun Mexico where is never cold, can I run this car with out a thermostat, the one just went & by the time a go there with the part maybe another month and the local mechanic said that we could just remove it and it would be fine, is that true??
hardlymoving (author) from Memphis, TN on November 14, 2016:
Could be a number of things to numerous to mention based on your stated symptoms.
Govin on November 14, 2016:
i have 1999 camry. It is stalling at stop lights, hesitating to accelerate in the morning when i first time, and sometimes NOT STARTING and just cranking. Will it be due to faulty temp sensor or T-stat?
armen bagdasarian on October 17, 2016:
could not get 98 cam v6 to give me a "ready" for evap or cat. Drove the heck out of it, started shotgun approach, noticed temp gauge mid scale and alternately cold. long story short, pulled thermostat, shiny spots on inner tube which houses paraffin. Rock steady temp, mid scale maybe problem solved.
Rusty on July 01, 2016:
Hello. I have a 2004 Toyota Camry. When the car heats up the temperature gauge goes above the normal operating temperate (about 3/4 way up to H) then stops. the fans do not kick on. It never makes it all the way to the H. If I turn the AC on the fans run. The heat and AC both work fine. Any suggestions?
hardlymoving (author) from Memphis, TN on June 22, 2016:
A collapsed hose indicates a broken/defective radiator cap.
Dustin on June 21, 2016:
Hi, I've had a lot of problems with d hoses and such.. Just replaced timing belt water pump thermostat radiator and other such hoses and other things involved with the cooling system.. My upper hose is collapsing in in itself (brand new) I need to find a hose that will stand up and stand out rather than crumble and to effectively burp the system of any air... And I don't have a no spill funnel to help w the job.. Any advice or help would be greatly appreciated. 99 Camry ce 2.2 160,000 miles
hardlymoving (author) from Memphis, TN on May 13, 2016:
Yes ... it could be a defective thermostat. Also, low coolant levels will cause erratic temperatures.
sunlestial on May 12, 2016:
I have a 08 Solara and the temp gauge rises too high. My previous vehicles' gauge always set near the half-way mark bwtn H & C.
I don't think this is normal.
Driving @ 65pmh its @ halfway but once on city streets it rises to 2/3 towards H.
It has never ran into the orange. Once getting to 2/3 a fan will kick on and the temp will lower to just above half-way.
I plan to have the thermostat changed in hopes its something simple..
hardlymoving (author) from Memphis, TN on January 10, 2015:
Could be either a defective water pump or a clog in your cooling system. If your coolant is muddy in color, you've probably have a clogged radiator. If so, try some coolant flush. Also check that the radiator fan goes on after the car exceeds normal operating temperature (gauge is in between the Hot and Cold).
mario on January 10, 2015:
My car is overheating, i changed the thermostat still overheating, i can hear the hoses sometimes squeezing together and the heat isn't working either before this it worked perfectly but we had below freezing temps recently
hardlymoving (author) from Memphis, TN on November 01, 2012:
Replacing the thermostat is a good start. If it doesn't properly open, your car will overheat even if the fan goes on.
H on November 01, 2012:
I have a problem with my camry 1997,, the engine heat up but the fans don't work!! I checked the fuses and relays and they were fine.. I unplugged the temp. Sensor (located in the bottom of the radiator) then the fans started to work whenever I start my engine but still the engine heated up so I just removed the thermostat and tested it by putting it in a hot water.. The thermostat doesn't work therefore I'm going to change them today.. I hope this will solve my problem..
hardlymoving (author) from Memphis, TN on March 22, 2011:
It's not a bolt but a stud which is like a bolt but doesn't have a bolt head and has threads on both sides. To remove it, you'll need a Stud Removal Tool. What it does is grabs onto the stud and with a attached rachet wrench, you can twist it off... or you can use a Vise Grips. Here's the link to the Stud Removal Tool ... it's less than $10:
janddirr on March 22, 2011:
Thanks for the informative post. Unfortunately for me, while I was tightening the nut to the thermostat housing bolt, the bolt snapped off. I have since purchased a new bolt but can't find anywhere in the repair manuel how you remove the broken bolt and replace the new. Can u help me?
hardlymoving (author) from Memphis, TN on January 19, 2011:
And that's why I write these 'How To' Articles...so you can weed out the honest from the dishonest mechanics or do it yourself,
Jack, Raleigh, NC on January 19, 2011:
Thanks for your fine article. It describes the overcooling problem we are having with 98 Camry and the exact same response from two local repair shops. Both wanted $200 to replace the thermostat. Absolute robbery.
hardlymoving (author) from Memphis, TN on January 08, 2011:
Thanks. Happy motoring!
gz on January 08, 2011:
excellent description on how to do it.
it worked perfectly for me.