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.

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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


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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.


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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.


New Camry water temperature sensor


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.


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.

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: 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.

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.

Comments

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:

KK,

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:

Govin,

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.

See more: Engine Maintenance: How Long Does It Take To Change A Timing Belt & Water Pump?

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:

Dustin,

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