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when i drove my car to a normal temperature, (the gauge needle is about at the mid-point, as normal). but I suddenly found out my car engine temperature gauge needle dropped down to bottom after i turned the heat on for 1-2 minutes. The outside temperature was abt 38 degree. Do you guys have this problem before? Thank you. My car is 2000 civic.

 
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mine did that once i had the heater blasting it was a cold night and the needle started dropping not much but noticeable. it went back up after a few minutes but i think that is just the engine cooling down when the heat is being diverted to another area.

 
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yes, the temperature went back up after i turned the heat off, but i turned the heat on again for minutes, then the needle dropped again, i did it over and over, it turned out the same.

 
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on cold nights yes its hard for the engine to warm up. If I don't leave mine in d3 so the rpm is higher, it sometimes takes forever or doesn't reach operating temp at all. When you use the heater, it diverts coolant to the heater core which cools it down even more.

 
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actually the heat is not hot even i turn it to the hottest mode, what do you think of problem is? should i don't turn the heat on so far? don't let the engine cool down when i am driving, until i found out what the problem is.

 
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it is okay if your engine run alittle cooler than normal but if it is higher than you have a problem. dont worry about it.

 
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you guys actually trust that gauge to mean something? Its like an idiot fail safe.
All it is is the cold stuff in the heater core getting put back into circulation. It shouldn't drop any noticable amount, but I wouldn't put any stock in the accuracy of that gauge at any time.

 
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Yeah, the coolant in the heater core does not circulate untill you turn the heater on. So if the rest of the car is warmed up, then you turn the heater on, you have "injected" cold coolant into the system, it can make the needle go down. It's best not to do this, the shock of having 200 coolant then 10 degree coolent is not a good thing. Over time it may cause cracks, but I may be just talking out my crack Anyway, it probably won't hurt anything, but I turn everything on at once, then run back inside for 5 minutes.

 
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good idea

 
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One day in band camp....

I mean in Germany... heh... we had to put cardboard in front of most of the radiator to keep the car warm enough TO heat. It's probably normal if it's real cold outside, but it could also mean you have some air in the system. Turning the heater on full blast on a hot day when your engine is overheating may seem crazy, but it does pull a lot of heat away from the motor. The most uncomftable drive I ever had was from Los Angeles to Mammoth in a subaru wagon with a clogged radiator. Windows down, Heat up full blast through the mojave desert. Made it, though, without killing the engine. Was able to get a new radiator shipped there later.

So it also works the other way when it's really cold. It'll suck the heat right out of that little aluminum block.

Cars are such fun

 
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i asked my friend abt the problem of my car, he said it might be the thermostat problem.