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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4818
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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I have a 1999 Toyota Camry LE with the 5s-FE engine and I

Customer Question

hello, I have a 1999 Toyota Camry LE with the 5s-FE engine and I have an overcooling problem. I have done quite a lot to fix this problem with no success. I have posted a well informative post on another site that has a lot of fixes I have already done. I will also post a video of my problem and I will copy and paste my question from the other site.
thank you in advanced.
Fourm Post:
Video post:
Hello, I have a 1999 Toyota Camry with the I-4 2.2 Engine. (5S-FE)
My engine does always seem to run cold for no particular reason. I noticed that it happened slowly over the course of months the car would run a bit colder and just a little more cold next week. I Thought the Thermostat was stuck open.
So I just changed it with an aftermarket one. Took it for a test drive and Still the same thing. Replaced it again this time with a new OEM Thermostat. It helped a bit more but still much too cold. Other things I have done is check the Coolant Temp sensors. I have 2 of them One is for the ECU and one is for the Gauge on the Instrument cluster. Both appear to read the same. ECU says it runs about 145-160F.
I took an inferred thermometer to the engine and I get almost the same reading. My heat also does not work that great. In Traffic everything is nice and warm and great.
Im at a loss of what I need to do. Cooling fans Turn on as they should at 205F and turn off around 190. I threw cardboard in the Rad and that has helped a lot.
Thanks for any help provided
Things I have Done:
Removed Air In cooling System twice
Changed Thermostat (New OEM is Installed)
Checked Coolant Temp Readings
Compared Coolant Readings to Actual Engine Temp
Checked Fan Relays
Cardboard in Rad.
Changed Coolant temp Sensors with known working
Checked for Codes Stored and Found none
Using 50/50 ish Collant Mix
Checked make sure belt is going right way
Removed Thermostat and saw Further Temp drop
All coolant hoses feel about the same temp so there is no clog anywhere
If you need any other info let me know. I also have access to the Toyota service manual
Submitted: 1 year ago.
Category: Toyota
Expert:  Toyota Service replied 1 year ago.

Hello. Welcome to Just Answer. Please allow me to assist you. I am not sure exactly what you are saying here, perhaps you can clarify. As I understand it, the car runs 'cold', as in not enough heat output, but, your coolant temperature is reaching 205 when the fans come on and they shut off at 190. Is the no heat condition the prime concern?

Customer: replied 1 year ago.
but the engine itself can not maintain operating temperature while in motion therefor no very much heat output. the fourm link and the video link help out a lot for information.
Expert:  Toyota Service replied 1 year ago.

Please allow me to ask if the check engine light is on.

Customer: replied 1 year ago.
it is not
Expert:  Toyota Service replied 1 year ago.

That is very interesting. On this car, the computer would read a low coolant temperature and display a code for that condition.

Expert:  Toyota Service replied 1 year ago.

Let's do this: Get the engine warmed up (when the fans come on)...Then take the infrared thermometer and point it where the heater hoses enter and return from the fire wall. With the heater fan on High, measure the temperature of each hose please. Advise of the readings.

Customer: replied 1 year ago.
The upper radiator hose reads at:182F
Lower radiator hose reads at:162F
Heater core inlet reads:146
Heater core outlet reads:120
Engine valve cover reads: 213
Fans where on at the time of reading.
Customer: replied 1 year ago.
ECU temp is at 197F and coolant needle reads normal
Expert:  Toyota Service replied 1 year ago.

What is the temperature of the thermostat housing (engine running)

Customer: replied 1 year ago.
171F at the start of the housing and goes to 194F toward the engine.
Expert:  Toyota Service replied 1 year ago.

Your thermostat housing is reading too low. It should easily be 190 degrees or a bit higher. Your temperatures are consistent with a 180-182 degree thermostat. Before I did anything else, I would put a 192 degree thermostat in the engine. If you want, get a pot of water and suspend the current thermostat in water on a metal hook. Bring the water up to temperature on a stove. Using a thermometer, measure the temperature of the water. If the thermostat moves/starts to open, any at all, around 178 degrees, you have a thermostat that is incorrect in the package. Mispackaging is, unfortunately, rather common.

Customer: replied 1 year ago.
Alright, but what about when I am traveling down the road and the temperature drops to about 150. Should it not almost close to allow coolant to heat back up? This winter I took out my cardboard in my radiator and the temperature dropped down as low as 120.
Expert:  Toyota Service replied 1 year ago.

As you are traveling down the road, air is rushing thru the radiator. This is cooling the coolant in the radiator. When the thermostat opens (in this case, prematurely), you have cold coolant entering the engine. The thermostat opens to allow the hot water in the engine to escape into the radiator, not back it up. The prime function of the thermostat is to maintain a specific operating temperature. It opens and closes, as needed, to maintain 192 degrees at all times. If the stat is opening too soon (defective) or rated to open at 180, your temperatures will easily be 150.

Customer: replied 1 year ago.
Alright, in my past time of fixing this. I have a friend who just so happens to have a 99 Camry as well. I was curious at what his temperature ran at. It was constant around 190F so I asked if we can swap stats. We did. His still ran fine and mine still ran too cool.
Customer: replied 1 year ago.
I will try a high degree thermostat and see if it makes a change and I will report back went it is done.
Expert:  Toyota Service replied 1 year ago.