I have a 94 base coupe with 119k bought with 105k and until last week haven't had a minutes problem. Driving 50mph in 6th gear coolant suddenly gushed through the passenger side headlight seam with so much force I thought I had run thru a pool of standing water. Looked down and analog temp gauge is pegged and digital, once I got switched over read 286 as I recall. Got stopped and towed to the garage. Tests showed no exhaust in the coolant and compression strong. Turns out primary fan not working and rad cap bad leading to overheating and coolant blowout. My concern is the car before this incident routinely ran right around 185 degrees sneaking up to 195-200 in the heat of summer but now runs 195-205 and temp outside is mid 60's. New 180 stat, rad cap and fans repaired and all working fine as far as i can tell. Could it be that there was a 160 stat in before and now the new norm is going to be 10-20 degrees hotter? Also noticed that the driver side fan comes on around 185 and don't remeber that being the case before but never really payed attention that much. Just squirrelly feeling since it always ran cooler and if anyone has had similar experience I would appreciate any comments advice. Thanks.

 

The stock LT1 C4's typically run around 190 - 195 on the highway. The cooling fan is controlled by the PCM, and will let the coolant temp get to 230 before it pulls the temps back down.

It's possible that you have a lower temp thermostat in the car - and it's possible that the PCM has been reprogrammed to alter the cooling fan on point.

The 280 coolant temp is a bit scary - but hopefully - you didn't hurt anything. BTW - just about any car out there - including a Vette does NOT need a cooling fan when traveling at more than about 35 MPH - the airflow into the grill and through the radiator at that speed is more than sufficient to cool the motor - so if you were really driving down the highway when this happened - I would spend some time checking the cooling system - it sounds like you might have other problems. The C4's are known for accumulating crud in the area in front of the A/C condenser, and between the condenser and the radiator. It can be a PITA to get stuff out of there - but it might be necessary. I'd also check for a clogged rad, or a thermostat that isn't opening fully (which it sounds like you already replaced). Just my $0.02 worth.

 

Thanks for the response. New stat and rad cap. Trash cleaned out by the shop so I didn't see the junk ut the shop said it was nasty. I've been driving with the new temp for a couple weeks now. I haven't seen temps over 205. Still not sure why the temp climbs faster than it used to. Maybe rad still not flowing right.