Mechanics

RUNS HOT WHEN STOPPED, BUT COOLS BACK DOWN WHILE DRIVING.

1998 Chevrolet Lumina • 290,000 miles

My lumina starts to heat up when stopped. I have to turn the air off and put in neutral until light turns green. When I start driving again, the temparture gauge goes back down. I have a new radiator, new thermosat, new hoses, and new spark plugs. I need help. Cant afford another costly repair. Please help. When I turn car off, I smell a mixture of antifreeze and/or gasoline. It smells awful !
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Michaelrodgers
June 27, 2012.




Have you checked if the radiator fan is turning on? When moving, you have natural air flow through the radiator. Since that cools it down, you know all the other parts are okay and working.


Caradiodoc
Jun 27, 2012.
Yes, I have checked and both fans work. Someone said I might have an air bubble in the line. Open valve right by thermostat. I will try that and should I check the cat. Converter?


Tiny
Michaelrodgers
Jun 27, 2012.
Catalytic converter is in the exhaust system. It can promote engine overheating if it's plugged but the engine would have almost no power at all. You'd have a real hard time reaching 25 mph.

If the engine cools down, as you said, at higher speeds, you have insufficient air flow through the radiator at low speeds which is a fan problem, or you have insufficient coolant circulation which is a water pump or belt problem. If the engine gets too hot and the air from the heater is cool, suspect circulation trouble. The hot coolant is not getting to the heater core in the dash and to the radiator. At higher speeds the engine is running faster so the water pump is too. If you can carefully shift into neutral while driving on the highway and coasting down a long hill, with the engine idling, if it overheats while still at speed, it's poor circulation. You can do the opposite too. Put it in neutral while stopped and raise engine speed. The fan should come on. If it still runs hot, suspect poor circulation. If it doesn't get hot until you let engine speed come back to idle, suspect circulation trouble.


Caradiodoc
Jun 27, 2012.
I am putting it in neutral at long red lights and turning the air off. Air is still very cool when driving. The raditor and water pump are only a few months old. I cranked the car the other day in park with the air contioning on and opened the hood and both fans were turning. How can you check if it is the thermostat or the water pump?
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Tiny
Michaelrodgers
Jun 27, 2012.
If you can run at normal temperature on the highway, the thermostat is open. When it runs hot at stop lights, if it cools down a minute or two after you raise engine speed in neutral, the water pump or a loose belt are suspect. Since the water pump is relatively new, a loose or eaten away impeller are not likely but a loose belt would be more common. Typically you'll also get a belt squeal, particularly when turning at slow speeds or when stopped, and you'll have weak or pulsing power steering assist.

Since the radiator was replaced, when the fan turns on, check that air is blowing the right way, toward the engine. I've seen stranger things before. Someone could have repaired the electrical connector and switched the two wires around. I know that sounds silly but it just takes a second to check.

Also look for a missing rubber gasket under the front and rear of the hood. The front one seals air from going through that gap and forces it to go through the radiator. That is more of a problem at low speeds when the air flow relies on the fan.


Caradiodoc
Jun 27, 2012.
If you smell antifreeze and gas together you need to have a combustion leak test done to ensure u don't. Have a blown head gasket.


Tiny
Mikederouin88
Jun 29, 2012.
If there is a bleeder valve you do need to bleed it after changing water pump and radiator. At idle air pockets will cause your hoses to collapse and over heat. Also is the vehicle actually getting hot or is it just reading hot on your guages?


Tiny
Mikederouin88
Jun 30, 2012.
Michaelrodgers, what's the verdict with this? Have you been able to determine what the problem was/is, or do we need to take it a little further?


Rivermikerat
Jul 30, 2012.

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