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Engine Overheating


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My 92 sc400 coolant started pouring out of my resorvar couple of months back while driving from la to san diego. After that time it did not do it again. then recently I was driving home from work and stopped at a drive thru to get some food and it started pouring out again. If I let it heat up and idle it will overheat, but if I drive it it cools down. I noticed that the electric fan seems to spin slow at high temps, but when I turn on the ac it spins fast. What could it be and suggestions PLEASE!! :cries:

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Your car is obviously overheating. You need to find out why. Could be the thermostat, waterpump, antifreeze condition or failing radiator. I'd replace the thermostat first and also check the condition of the antifreeze.

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When I checked it yesterday, the electric fan was spinning slowly at high temp. When I checked it today I unpluged which I think is the ac switch at the bottom of the radiator under the electric fan resovoir and the fan started spinning faster. The only problem is that it cools down, but it goes back up. I would then have to rev the car for the coolant to flow faster for the temp to go back to normal temperture. Does anybody know if the fan spins at 2 different speeds at different temps, or it gradually spins faster as the temp goes up? And if by unpluging the ac switch which makes the fan faster, is this the fastest the fan can spin? Or it is completlely something else? HELP!!!!!!!! :wacko:

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I believe the fan does spin at two different speeds. It should spin faster when the AC is turned on to give it a boost in cooling. Sounds like you may have a failing water pump from what you are telling me. Have you checked the coolant condition? Go get one of those cheap coolant testers from the auto store if you haven't. Do you notice any coolant at all dripping anywhere?

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I think it is the waterpump. It feels loose when I shake the pulley. There is no leaks though. Thanks for the advice. I have another question. How do you fill the radiator with antifreeze. There is no radiator cap on the radiator. just the resovior. The manual says I have to put it in the inlet hose while the car is running. Is this the top radiator hose or the small hose that connects the radiator to the resovior? Thanks again. :huh:

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you may have a problem with the thremostat switch to turn on the fan to high speed for temp as the a/c circuit runs fine

what happens if you just keep the a/c on to cool it?

the fan always runs and gradually adjusts speed as needed

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I don't think it is the waterpump. The pulley I thought was part of the water pump was the electic fan pump pulley. When I got taking most of the pieces of my car to see the water pump hidden behind the electric fan pump, the water pump looked like it was changed recently. it looks pretty clean. I bought the car in february last year. I think the system needs to be burped and still something is wrong with the electric fans from turning on on high speed. I know it is not the relay cause this car don't have electric fan relays. I hope to god it is not a bhg. I still need more suggestions. The electric fans consist of a solenoind, ac switch, coolant temp sensor and electric fan ecu. I already have bought and replace the coolant temp sensor. no luck.

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Now I have worst problems. When I checked the water pump and found out it seemed to be replaced recently. I removed the thermostat to see if water was flowing right, then I started the car. It was running fine. I was adding water in the inlet hole on the thermastat housing and then all of a sudden the car dropped in idle and started to idle rough.

I was a idle like the timing was off or one of the pistons was not working. Then it smelled very rich and the piping and cats under the car started to smoke. Every time I try to rev the car the needle will jump all over the place. But there was no smoke coming out of the tailpipes.

I checked all the plugs and they all looked fine. No oil or coolant. Then I checked the timing marks and they were aligned in the right spots. I checked all the plugs to the sensors and they were fine and connected. Is there any sensor that went bad in my car that would make the car overheat and start to go bad and make the car run rich and rough? By removing the thermostat had to do something with it? I am more confused and fustrated than ever before. Please anybody with some advice.

92 Lexus SC400 stock

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it seems to me that sc400 has problems with coils because that just happened to me about a week ago along with another person. those symptoms are exactly what happened to me it happened all of a sudden and when i gave gas my tach would drop to zero and raw fuel smell out the exhaust. as for your fan problem try check your hydraulic fan.

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Thanks Jzz30. I ordered another coil today. I am guessing now that the reason why my car is overheating is that the heater control valve is clogged cause my heater doesn't work either. I have been looking around the msg board and it has the symtoms. I did switch vacumm hoses and I still didn't get any heat. I hoping that is the problem. I'll post the outcome when I receive my coil.

By the way you from Hawaii. Howzitt!! Hows the weather. I was born there, went to Aiea High School.

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Im in San Diego. It is a nice hot day, but not too hot. But this weather is nothing like the great weather in Hawaii. Wish we had the cool breeze of the Hawaiian trade winds. We got winds here, but they come from the desert and they ain't cool.

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My car was doing the same thing 3month ago it was the "water pump" i changed it plus i changed the thermostat and now im having the same problem again but not as bad only on trafic and if i leave it on not driving, as soon as i hit the road it cools down. Anybody knows whats up with the overheating?

Could it be the Head Gasket ?

Plus im getting hot air coming out from the driver and passenger side on our feet, Dose this has anything to do with my problem?

Thx

Moe/Montreal

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Well I fixed the ignition problem it was the primary coil. Thanks again for all the advice.

Now back to my first problem, the overheating. I narrowed it down to the heater control valve, because one, it is a common problem for lexus v8s, and two, someone told me that if that is clogged it wouldn't circulate, also it tells the fan ecu to spin faster.

I know it is the fan, cause it DOESN'T spin faster at normal temp. And I know it can spin faster cause if I unplugged the coolant temp sensor, which is located on the radiator, it DOES spin faster. I found a engine cooling fan-hydrolic repair on this forum and it says that the fan ecu gets info from the heater control valve.

I hope this is the problem, cause I am starting to run out of money. Has anyone tried cleaning or repairing the heater control valve?

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