2003 2.4 Overheated w/o temp gauge showing it
 

Hello. This is my first visit to this website. I hope someone can shed some light on this.

My wife was driving the 2003 Camry yesterday when the "Check Engine" light came on. She noticed that the AC had started cutting off then would come back on. I needed to use the car this morning, so I took it on an errand. The AC seemed to work fine for me, but when I made my stop and came back to the car, it was hard to start. Thinking this was the cause of the "Check Engine" alert, I headed straight home. As I turned into the driveway, the car died. I opened the hood and saw steam coming from the coolant tank. I carefully checked and found that the radiator was COOL. The engine had overheated, but the dashboard temperature gauge never went over the midpoint. I'm guessing that the engine shut-down was done by some temperature sensor somewhere. I figured that the problem might be the thermostat stuck closed or water pump not working. I had the car brought to my mechanic who looked at it and said it was just very low on coolant. He's going to flush the cooling system and change the thermostat anyway, but I don't have a good feeling about the whole thing. If the car overheated to the point where the engine shut down, why wouldn't the temperature gauge on the dash have shown it? If it was just low on coolant, why would the radiator still be cool? I would think it would at least be warm since steam was coming out of the coolant tank. If the car was starting to overheat yesterday when my wife was driving it, would this have caused the AC to start cutting out? Like I said, it's just not adding up to me. Appreciate any insight.

If the check engine light is on, have the mechanic read any trouble codes. The light comes on if a trouble code(s) is set.

There is no safety feature to turn the engine off if it is overheats.

If the thermostat was stuck closed causing a hot engine. The temp gauge would indicate this unless low on coolant.

How cool is cool? Could you put your hand on the radiator top and keep it there without burning? Typically coolant temp is around 199F.

Suggest the mechanic conduct a coolant system pressure test to determine if there is a leak.

It has happened on this model engine that the head bolt threads pull out of the block. This can cause coolant leakage and a blown head gasket.

A blown head gasket can cause overheating and or exhaust gas in the coolant causing steam. Have the mechanic feel for coolant behind the engine in the area of the foam insulation for the intake manifold. Then test for exhaust gases in the coolant.

2003 Overheating update
 

toyomoho - thanks for the reply. Here's what has happened since I submitted the post:

The mechanic flushed the cooling system, replaced the thermostat and the radiator cap, then did a pressure test. The pressure test reportedly came out fine, no leaks. The (short) test drive was OK, the car didn't seem to overheat. The trouble code from the "Check Engine" light was "overheating" but he didn't give me (and I forgot to ask) about the exact code number.

Yes, when the problem occurred I could put my hand on the radiator and it was absolutely cool, yet the radiator cap was too hot to touch. When I got the car home after the repair, the radiator was warm. Don't have enough experience with it to know what feels normal.

The main question for me remains why the dashboard temperature gauge didn't indicate an overheating problem. The mechanic couldn't offer any definitive explanation ("could be the sensor, could be the instrument panel", etc.) and without being sure, I can't trust the gauge.

I have a few errands to run tomorrow so I plan to look under the hood during my stops and get a feel (no pun intended) for what it's doing.

Again, thanks for the reply.

Low coolant (fools temp sensor) plus a bad thermostat, water pump, etc. could cause a cooler radiator top.

The temp sensor on the engine can be checked with an ohm meter and the gauge tested.

Since the engine quit from overheating suggest keeping an eye on the coolant level in the coolant tank. The level will vary with engine hot/cold. Check after the engine has sat overnight and is cold.

It might go down after the flush do to air still being bleed out. Add more coolant and if not available add distilled water. After which the level should remain the same when checked cold.

Thanks for the reply. Your comment that "low coolant fools the temp sensor" is disturbing. Of what use is the temperature sensor and dashboard gauge if it can be 'fooled', allowing the engine to overheat without the driver suspecting a problem until it's too late? In any event, you made reference to checking the temp sensor with an ohmmeter and having the gauge tested. Can you elaborate?

The temp sensor works by changing electrical resistance with temperature. This change results in the gauge needle moving one way or the other.

Wonder if there is something else going on here. As such monitor the coolant level in the overflow tank.