1995 Chevy Corsica Overheat then not

The Joat · Posted at Thu Nov 05, 2009 10:46 am

Engine Cooling problem
1995 Chevy Corsica 6 cyl Front Wheel Drive Automatic 125000 miles

After changing the water pump and refilling the system with fresh coolant. When first started after being allowed to cool the car will warm up and the temperature will continue to climb all the way up to the H indicator on the gauge. It will sit there for about 1 minute and then it will drop back down to less than the first quarter mark on the guage.
This is where it has been running since I replaced the thermostat with a 180 degree model at the same time as I replaced the radiator in the fall of 2008.
Also the low coolant light has been on and stays on since I changed the water pump, despite the resevoir being full. Coolant is being pushed out from under the new resevoir cap when it heats up, but probably because I have overfilled it. I also installed a new heater core about 2 months ago. I have the heater controls turned to full heat, and as the car warm up it starts to produce warm air, but when the temp starts to climb higher the heater temp cools off. This seems to me to mean that I am not getting the cooling system filled properly, but I have removed the bleed valve while filling and also unhooked a hose higher on the block than the bleeder valve and was able to get coolent to run from both places. The low coolant light came on and stayed on for a week after I replaced the heater core, but the temp guage acted normally at start up and all other times. The temp only rises to the "H" once at start up (after running around 5 minutes)and then runs normally no matter traffic or speed till the car is turned off and cools down completely.
Thanks for any help with this question. Its a weird one.

pear69 · Posted at Sat Nov 07, 2009 6:46 pm

Was there a 180 degree t-stat before this happened? If not, then you should replace the radiator cap with one that is rated for 2 to 5 PSI more than the stock one..A little higher PSI is ok..
Also, even if there was a 180 degree t-stat, you should still replace the radiator cap..

The Joat · Posted at Sat Nov 07, 2009 9:27 pm

Yes, it had the same thermostat since the radiator was replaced in summer/fall of 2008.
Coolant fill tank cap was replaced at same time as heater core. About a month ago.

Thanks for the quick reply, but that was already done.

John

95v6corsica · Posted at Sun Nov 08, 2009 9:31 pm

Ok, this may not be the problem but it is something you should have checked just to be safe...there is a chance your Lower Intake Manifold gaskets have gone bad and your leaking coolant causing the low coolant level light to be on, these cars have that problem, i have the same car as you do.

If that is not it than my next guess would be your coolant temperature sensor and coolant level sensors have gone bad.

Post back and let us know when you check these.

pear69 · Posted at Sun Nov 08, 2009 9:46 pm

As long as you can physicaly see that the coolant is at the proper level in the reservoir, the low colant light is probably a bad coolant level sensor.
Adjust the coolant level to the proper level when cool and see if the coolant blows out of the reservoir cap again. If it does, then totally flush the system with a good cooling system flush like prestone system flush..
The lower intake gaskets do fail quite often on these engines, but your symptoms do not (IMO) indicate this.

The Joat · Posted at Mon Nov 09, 2009 4:34 pm

The coolant does blow out of the resevoir cap.
Unfortunately the car is currently waiting patiently in the Philadelphia Airport economy parking lot, to take me home on friday night at around midnight when I get home from OKC, where I am currently on business. LOL I think its time for the cooling system flush. I may try blowing a couple of those small return lines out with compressed air first though.
Thanks to all of you guys for the replies.
I'll be sure to let you know how it works out.
It really is a great car and I'm missing it this week as I drive a new HHR rental. What a hunk of junk.
LOL