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I've been noticing that my car has a tendency to overheat for some time (a few months maybe). I finally investigated it and found out that my cooling fan wasn't coming on, even though the car was clearly getting hot. I went through the electrical schematics, and figured out that the temperature switch (the one that plugs into the bottom of the radiator) was the problem. I bought a third-party switch, and replaced my old one, and I noticed that now my fans were coming on, but only when the gauge was just about in the red. I went back to the store and exchanged it for another one, and this time the fans didn't switch on even when the gague went into the red. I was told that for this part, this sort of thing can happen, and the only replacement switch that will work is one I get from the Toyota dealership. Has anybody dealt with this situation before? The car is a '95 Camry, 4 cylinder 2.2 L engine.
I don't think that's the problem because when the car has been running for a while both the top and bottom radiator hoses are hot...the thermostat is also only about a year old
Also, when I just unplug the wires that go to the switch, causing the fan to run continuously, the car doesn't overheat. If the thermostat were stuck I'd have trouble even with both fans going at full blast.
Last edited by tankpower2; 09-26-2005 at 11:36 AM.
I've been reading up on this some more, and I'm wondering: is it possible that the switch isn't getting as hot as the engine coolant due to air-bubbles in my radiator? If so, how can I purge the radiator of air?
i doubt you have an air bubble at the bottom of your radiator. the next thing i would check is the green cooling fan relay in the main fuse box and the coolant temp. sensor located on outlet(or inlet?) pipe on the tranny side of the motor. according to the haynes manual, the resistance (measured with a multimeter) between the pins of the sensor should be 2,200-2,700 ohms when cold and 280-350 ohms when hot(180-200 degrees). to check the relay apply voltage across pins 1 and 2 and check for continuity between 3 and 4.
I've tested the relay and I'm sure that it's working. I also just checked the main coolant temp sensor, and I got the right values. I'm beginning to think that it may be my thermostat after all. I noticed that when I let the fans run continuously, the bottom radiator hose stays cool. If I let the heat build up, and my temp gauge rise, the bottom hose heats up, but much slower than the top hose, and it never gets quite as hot. If the thermostat is stuck closed, could I still see a normal range of temperatures as long as air is going through the radiator?
if you have a faulty thermo...chances are it'll be stuck open.
how is it when you are at speed? do you over heat?
but from what you said about the fans---on, gets cool, off, gets hot
i say look into the thermo...and figure out why when your engine is hot, the fan doesn't come on by itself.
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When I'm driving say 30-40 MPH steadily, I don't have any problem with overheating, only when I'm in a stop & go situation, or driving around a parking lot. As far as the cooling system goes, the only components that I'm not sure are working properly are the thermostat and the fan switch. Does anybody know of a way to be sure that the thermostat is working short of pulling it out?
I think I finally figured out what's going on. I'm pretty sure that the thermostat is stuck closed, and I wasn't noticing that because the bottom hose was heating up due to contact with the thermostat housing. I held the engine around its normal operating temperature by running the heat on low, and the bottom hose didn't get hot. For good measure I checked the resistance across the ECT temperature sensor and got 350 Ohms, which should correspond to around 180 degrees. Thanks for all the replies.
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