'97 Saturn overheating


#1

My 1997 Saturn SL has had an odd overheating problem for several years now. When idling the engine starts to overheat, but the fan does not kick in until/unless I turn on the AC.( I do a lot of idling, as I work from the car a good deal.) I’ve had the car serviced, even had the fan specifically checked in the shop, & had the AC components changed out last year (whole other issue, barely blows cool air). But the overheating abides.
Any suggestions?


#2

If the fan is not coming in when idling, that’s the problem. If you took it in and had the fan checked, why didn’t they diagnose and fix the “fan doesn’t turn on” problem? What did they tell you?

Either the fan motor is bad (there are two separate fans, and one obviously does work) or the fan relay is bad, or the coolant temp sensor. There 's not much else thay could be wrong and it’s not difficult to diagnose. You just need a competent mechanic.


#3

+1 to jesmed’s post.


#4

The Saturn only has ONE fan, not two like most Japanese cars. There is only one relay so if the fan comes on when the AC is turned on, then the fan motor and relay are both good. That only leaves one other item, the ECTS (engine coolant temperature sensor) and Saturn’s are notorious for issues with their ECTS.

The ECTS must be replaced with a factory ECTS from a GM dealer. Saturn’s for some reason are very sensitive to this, the aftermarket sensors do not have a good history in Saturn’s.

BUT, before replacing this sensor, I would thoroughly clean the contacts in the connector. These are subject to corrosion and I suspect that many times, if the connector were cleaned first, the sensor would not have to be changed. You can get a spray contact cleaner at Radio Shack or you can try using a spray MAF cleaner available at any auto-parts store.

The ECTS is located at the base of the head, drivers side about in the center. Its sometimes hard to see.


#5

I should add that the fan won’t come on until the temp gauge is about at 3/4 scale. If you aren’t getting that hot, you aren’t really overheating.


#6

Good info, keith. My mistake about the fans.

About getting a new ECT sensor…this guy says the old sensors cracked because they have ceramic tips, and he recommends getting an aftermarket sensor with a brass tip that won’t crack:

http://mike-thomson.com/blog/?p=1338


#7

The replacement sensors sold by GM have the brass tips, but if you can get an aftermarket sensor with a brass tip, then it should be OK. Many aftermarket sensors have plastic or ceramic tips and they do not last very long.


#8

If you have a DVM, it is fairly easy to measure the resistance of the sensor and see if it meets spec or not. Testing the old sensor would provide a clue that you are working on the correct problem or not. And would help prevent installing a defective new sensor.