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ase_master327, Saturn Technician
Category: Saturn
Satisfied Customers: 5288
Experience:  +15 years exp.with Saturns. 5 time Expert of the Month. Bumper to bumper diagnosis and repair.
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97 saturn sl2 dohc overheats when sitting. Water pump replaced

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97 saturn sl2 dohc overheats when sitting. Water pump replaced 6 months ago. ETC replaced (cracked) 2 months ago. Radiator flushed a few times.
Hi, thanks for asking.

The frst thing you should be sure of is that the cooling fan comes on when the engine gets warmed up. If not.. then we will look into that part of the system. This would involve the coolant temp sensor, wiring, relay fuse, and even the fan motor itself.. and in rare cases, even the computer which sends signal to the relay to turn on the fan.

If it does come on, then we will need to look for clogs in the radiator, or even dirt buildup on the fins of the coil that would block air from coming through the core while it is solely relying on the fan (vehicle not moving) to pull the air through the radiator. So.. Let me know what you find if you need anything else.

Hope it helps!
Customer: replied 7 years ago.
Fan does not come on to cool radiator down. It will come on when AC is turned on.
Does the temperature gauge ever come up to normal?
Probably so, huh?
Customer: replied 7 years ago.
temperature gauge goes over halfway mark and above. If I turn on AC to turn fan on temp drops
OK cool! that suonds like a problem with the relay!

It is in the underhood junction block... Try swapping out a known good relay with it (like the fog lamp relay, or another just new one), and see if the fan comes on when the engine warms up.. It is a fairly common problem, too.

Here is the relay views so you know which is which:

Hope it helps.
Customer: replied 7 years ago.
already did that...
Hmmm.. .I see the problem looks to be something to do with the coolant temperature signal actuating the relay.. That is done with the PCM.

So I would say.. since you know the sensor is good.... Make sure the right signal is getting to the computer. Here is the resistances:
.. and here is the diagram mof the switch, so you can see which pins the wires go to on the PCM:

OK.. for the computer to turn on the relay, it needs to have a signal saying that the engine is up to 220 degrees.. And it turns it off at 210 degrees.. or so..

Once you get the desired resistance at those terminals , yuou should have power shoot out to the relay.. Here is a pdf of which pin that is on the computer...

If you dnon't get a signal there.. well, the circuit in the computer looks to be fried.
If there is power there, then there is a break in the wiring between there and the relay. I can tell you that sometimes the terminals push out of the relay sockets.. and even when they crimp the connector to the wire... it wears into and actually breaks the wire causing a bad connection that is very hard to find!

If you still don't find the problem, then it will have to go to a shop to be hooked to a scantool that can communicate with the computer and activate systems for testing, etc... This is a very expensive piece of diagnostic equipment, not just a code reader...and only a qualified professional will have access to one.

Hope it helps.
Customer: replied 7 years ago.

I will go over the info tonight and see if the problem is a signal issue. I will send the accept tonight unless I have any questions.





Sounds good.
I will help all I can.
Customer: replied 7 years ago.

I won't have time to look at the car until this weekend. If you don't want to wait I will accept now. I'm not going to forget you. I just didn't want to accept and have the electrical turn out ok, then I would be back here again. Let me know





Doesn't matter to me... I will be here to help you as much as I can either way.

You must have gotten one of those email reminders, they go out after like 24 hours or something like that...
Customer: replied 7 years ago.
I went out to the car and started looking at it. I found that the fan does come on when the temp gauge gets close to the 3/4 mark and the fan goes off when it reaches the halfway mark... I did not notice it working before. I did reseat the Temp sensor. I don't think that it is normal for the car to routinely go over the halfway mark. The vehicle typically stayed a little over the 1/4 mark. Any ideas on this? Sorry about the mis info on the fan
You might want to address the thermostat, because letting it go 3/4 of the way to hot is a bit high... but not actually overheating.

The fan on this system is designed to come on at 220 degrees... on over 1/2 way.. and turn off at 213 degrees.. still a bit over 1/2 way.

If the engine is only running 1/4 warm... you are wasting gas and losing power.
Heat is your friend. The cooling system is designed to warm the engine up as fast as possible, and maintain that temperature.. .If the temperature is jumping all over the place, it could be evidence of a thermostat problem..
In your case... with this new information, I would have to say, there is no problem.. unless there is something to do withg the thermostat. The only way to test the thermoostat is to pull it out, and put it in water with a thermometer, and start boiling it.. with the thermostat suspended in the water.. and see what temperature it opens.. .and THEN compare it to the temperature rating that is stamped on it.. If you want to dig into it, and need service info on the thermostat, let me know.

As far as the misinformation on the fan working or not... I get things like that all the time, so it is really nothing new.

Hope it helps.
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