1999 Saturn SL2 99 SL2 occasionally overheating at idle

BILLY9999999

MEMBER
1999 SATURN SL2
4 CYL
2WD
AUTOMATIC
130,000 MILES

Works great majority of the time, car reaches temp (about a 1/4 on coolant temp gauge where its been for 10 years) and stays there.

Increasingly often, lately once or twice a week, when at at a stop and idle, car starts overheating and gauge rises slowly to half or higher and starts to run rough. Once moving again (getting air flow?) Gauge goes back to normal.

Any help on narrowing it down appreciated, is it cooling fan? Sensor? Thermostat?

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,645 POSTS

Hi:
If this only happens when you are sitting and not moving, chances are the cooling fans are not turning on. Once you start moving and get the air flow moving again, the temp goes to normal tells me the cooling system is working properly.

The next time this happens, pay attention to see if the cooling fans turn on. You could just let it idle in your driveway to check it.

Let me know what you find.

Joe

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Monday, March 29th, 2010 AT 1:24 PM

BILLY9999999

MEMBER
1 POST

Will do, but it is intermittent so may be awhile before I get the opportunity to check it when its overheating.

Question: on previous cars I've had, the fan was always on, these were old GM belt driven. On this Saturn whats the story: is it a variable speed fan, where it may look like it's running all the time, but is actually running at different speeds based on conditions?

Just wondering exactly what I should be looking for. Thx

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Monday, March 29th, 2010 AT 3:04 PM

JACOBANDNICKOLAS

MECHANIC
109,645 POSTS

Actually, they are electric. THey are mounted to the radiator and are part of the shroud. They turn on when a certain predetermined temp is reached. The temp sensor sends a signal to the computer (PCM) and then it sends a signal to the fan relay which in the end sends power to the fans. With the engine off and cold, open the hood and look on the back side of the radiator (close to the engine) and you will see them.

Let me know if you have other questions. Also, let it idle in the driveway to see if it happens.

Joe

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Monday, March 29th, 2010 AT 11:42 PM