Coolant backing up out of reservoir, overheating

JESSE987656789

MEMBER
1998 SATURN SL2
1.9L
4 CYL
2WD
AUTOMATIC
194,000 MILES

Gets up to the middle on gauge, coolant goes backwards out of pressurized reservoir. Changed thermostat, new reservoir and cap, new relay. The fans not coming on, but hot wired the fan and I know it works. Help!

Wednesday, June 20th, 2018 AT 5:50 AM

3 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

Have you checked the coolant temperature sensor? That would explain the symptoms of the gauge reading normal and not coming on.

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Wednesday, June 20th, 2018 AT 1:47 PM

JESSE987656789

MEMBER
2 POSTS

Have not replaced it but I will. I ordered new connector and sensor, I do not think that is it though. The person I bought the car from unplugged the check engine light and or wires and or computer or something, it does not come on when you turn the key on. Scan tool will not work for OBD, before I put the car back to how it was supposed to be the car did not do this. The people I bought the car from rigged it up oh, I put everything back how it was supposed to be, coolant flows constantly with heater on high and blower on high, not overheating, yet.

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Wednesday, June 20th, 2018 AT 3:50 PM

KEN L

MASTER CERTIFIED MECHANIC
48,345 POSTS

I would replace the engine coolant sensor and if that does not work go over the wiring using this guide following the fan wiring diagrams below. If the wiring is okay I would swap out the PCM for a used one to see what happens.

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken

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