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97 - 01 Toyota Camry Thermostat and Temperature Sensor Replacement

I. Replacing the Thermostat

New Camry thermostat with a new O-ring gasket
New Camry thermostat with a new O-ring gasket

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

Diagram:  Camry thermostat, gasket, and housing
Diagram: Camry thermostat, gasket, and housing

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

New Camry water temperature sensor
New Camry water 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.

Detached fan motor socket
Detached fan motor socket

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.

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Comments 18 comments

gz 5 years ago

excellent description on how to do it.

it worked perfectly for me.


hardlymoving profile image

hardlymoving 5 years ago from Memphis, TN Author

Thanks. Happy motoring!


Jack, Raleigh, NC 5 years ago

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 profile image

hardlymoving 5 years ago from Memphis, TN Author

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,


janddirr 5 years ago

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 profile image

hardlymoving 5 years ago from Memphis, TN Author

Hello Janddirr.

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:

http://www.amazon.com/16-Stud-Remover/dp/B001U6HIV...


4 years ago

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 profile image

hardlymoving 4 years ago from Memphis, TN Author

H,

Replacing the thermostat is a good start. If it doesn't properly open, your car will overheat even if the fan goes on.


mario 23 months ago

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 profile image

hardlymoving 23 months ago from Memphis, TN Author

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).


sunlestial 6 months ago

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 profile image

hardlymoving 6 months ago from Memphis, TN Author

sunlestial,

Yes ... it could be a defective thermostat. Also, low coolant levels will cause erratic temperatures.


Dustin 5 months ago

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 profile image

hardlymoving 5 months ago from Memphis, TN Author

Dustin,

A collapsed hose indicates a broken/defective radiator cap.


Rusty 5 months ago

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?


armen bagdasarian 7 weeks ago

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.


Govin 3 weeks ago

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?


hardlymoving profile image

hardlymoving 3 weeks ago from Memphis, TN Author

Govin,

Could be a number of things to numerous to mention based on your stated symptoms.

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