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Toyotapro, ASE master tech
Category: Toyota
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Experience:  ASE Certified, 10+ years Lexus and Toyota Certified
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1999 Camry LE: temperature gauge..sensation that car is overheating

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1999 Camry LE temperature gauge pegs out in the red zone during normal operation. Gives the sensation that car is overheating. Replaced thermostat, temp. sending unit sensor & radiator, fan sensor switch at bottom of radiator and confirmed that water pump is completely operable. Speculate that sending unit sensor's ohm value is incorrect by checking with an ohmmeter after removal. Also temp. gauge is faulty. Can you confirm?
Have you put a temp gauge on the radiator or a thermometer in the coolant when this happens to be sure that the car is not actually overheating?
Customer: replied 8 years ago.

no, i haven't. just judged by feel, did not have a thermometer at he time of diagnosis.

Chilton manual offers test methods that rely on feeling the temps of the top and bottom hoses.

Chiltons is a horrible guide in most cases, I need you to actually take a temperature reading when this is happening, just be careful not to burn yourself when removing the radiaotor cap.

Customer: replied 8 years ago.

Okay, i will. Is there some kind of failsafe in the car that if it becomes too hot it will

shut down? What is the normal operating temperature range if the cooling system is working well?

The only fail safe is when the engine melts down and stops running Smile, you do not want to do that. The temperature is controled by the thermostat rating, you said you put a thermostat in already so read the temp rating on the box, it should be around 180 on these cars.
Customer: replied 8 years ago.

Alright, thanks. I appreciate your input but, how can I be sure that the temp.gauge and the operating temp. is safe if it registers in the red almost as immediately as when the car is started?

How long does the car actually run before this gauge goes to red? I need a specific time frame here....
Customer: replied 8 years ago.
Approximately 5-10 minutes.
Yes this can very likely be a legitimate overheat then. You asked how to check to be sure the temp gauge is accurate, checking the actual coolant temperature is the best way to do all this, there is absolutely no reason to spend hours chasing wires and removing an instrument cluster just to verify normal operation, the temp gauges in the clusters neer act up on these cars, if the coolant temperature sending unit was acting up you should also have some codes. The fact that from what you are telling me about the car right now scares me because I think you are having a genuine overheat issue here....these motors do NOT withstand running hot at all and there is a good chance you will need a new engine and a radiator here. Most likely you have a damaged head gasket at this point. Just my opinion from my many years of experience with this car, take it how you wish. Sorry.
Customer: replied 8 years ago.
Okay, that's pretty sound advice. I respect your expert opinion. Thanks very much for your time.
Thank you for your prompt replies and allowing my input. Good luck!
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