Overheating, Possibly thermostat

MAXEOLSEN

MEMBER
1996 SATURN SW2
220,000 MILES

So my car has been overheating, and when it first started overheating the coolant would bubble up and the temperature gauge in the car was not even close to the red zone when it would boil. The head gasket has been replaced, along with the cooling fan which got rid of the bubbling and it no longer boils when the heat gauge is at about halfway. The water pump has been checked. My repair manual says that you can check the thermostat by feeling how hot the upper hose on the radiator is. If its hot when the engine is hot then your thermostat is stuck closed. I let the engine get up to about the red line and checked the hose, It wasn't cold, but it wasn't extremely hot either (you could leave your hand on it and you wouldn't get burned). I'm not sure how "hot" the hose is supposed to get, so if you know that would be a big help.

3 Replies

SATURNTECH9

MECHANIC
30,870 POSTS

So how high does the temp get when the cooling fan comes on?Most of the overheating concerns on those cars are caused by bad coolant temp sensors and or the connector going to it.I really cant remember the last time I saw a bad thermostat cause those engines to overheat. Usually when the thermostats go bad in those engines they run too cold and never get up to operating temp. My money would be on the coolant temp sensor its really common for those to go bad I have replaced so many of those I lost count.I have had my 1999 sl2 and replaced that sensor 3 time since I have had it. If you unplug the coolant temp sensor while the car is running the radiator fan comes on?

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Thursday, September 29th, 2011 AT 7:52 PM

MAXEOLSEN

MEMBER
2 POSTS

The fan comes on before the coolant starts to boil, and when I turn the ac on it starts right away, and the engine overheats faster with the ac on.

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Thursday, September 29th, 2011 AT 8:26 PM

SATURNTECH9

MECHANIC
30,870 POSTS

Have you checked the a/c condensor which is right front of the radiator and the radiator itself for fin blockage?Suck as bags sand debris animal hair etc?When the radiator fan is on can you feel a lot of air being pulled thru the radiator or is it just a little bit?Also have you checked the coolant temp sensor?Thats the number one cause of overheating on those cars. Also if you a good coolant cap and the temp gauge hasnt reached the red zone yet and its boiling out of the cap theres another sign you have a bad coolant cap. Or you could just have a bad coolant cap and its making it look like a overheating car have seen that one before also. Do you have temp gun?

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Thursday, September 29th, 2011 AT 8:34 PM