[jdgumbus]

Hello, I have a 1995 GT that sufferers from an overheating issue. I have tried everything I can think of to fix the issue to no avail. I have a brand new Mishimoto performance radiator with a Mishimoto performance fan, I have all new mishimoto hoses, a brand new aftermarket thermostat housing, a brand new 180 degree thermostat, and a performance water pump. Still no luck at this point. I didn't trust the car to run the fan on its own since it seemed to be coming on late so I wired it directly to a switch. All that accomplished was to slow the rise in temperature but it still would never stop climbing. To make sure it wasn't the gauge I got a AEM water temp gauge with stand alone sensor that I mounted in line with the upper rad hose. New sensor and gauge confirms cluster gauge was mostly accurate. I tried bypassing the heater core in case there was a blockage there but still no change. I cut out the center of the thermostat for constant flow and saw no difference. I tried burping the system multiple times to remove any air bubbles but still nothing. I also tried messing with the ignition timing which didn't help at all. And just tonight I did a head gasket test by checking if there were any exhaust gasses in the system and it confirmed there was none. At this point I have overhauled the entire cooling system but still the engine will not hold a temperature. Regardless of driving or sitting idling the temperature will climb. I had gotten it up to over 250 once just trying to make it home from work. So if anyone has any ideas or tips for me id greatly appreciate it as I cant think of anything else to try.

 

[Victor112487]

did you check the polarity of the fan its supposed to suck not blow and its a 3 wire system if you mix up one of the wires you will reverse the polarity of the motor. did you check ALLL the hoses including upper and lower radiator if not check the block make sure you don't have an intake blockage or someone may have put the wrong antifreeze or its calcium creating a blockage

 

[jdgumbus]

Update: I do suspect I had the polarity of the fan backwards. I wired it to a relay to a switch in the car so I can turn on the fan whenever I wish and that helped but the temperature still didn't stop climbing. It definitely spins the right way now it can hold a dollar bill on the condenser. The car also had a set of underdrive pullies on it which a mechanic had suggested could be spinning the water pump too slowly. I got a used stock one and put it on. It made no difference. Over the past couple of days I have taken the heads off to ensure the head gaskets were installed correctly since the previous owner said it had been rebuilt at some point. With no proof obviously. But they were installed correctly and were in good condition. All of the parts show obvious signs of overheating. The lower manifold gets progressively more brown on the bottom from front to back. The front two coolant passages are clean while the others are blackish on the inside. On the very back of the manifold there was a large collection of a white gooey substance inside. Inside the block there is a dirt like substance that lines the cooling jackets around the cylinders which could suggest compromised cooling surface area or a total blockage somewhere.

 

[Victor112487]

Well do an ENTIRE COOLAN FLUAH WITH THE BLOCK AND EVERYTHING the person before you could’ve put block sealer or something like that in the radiator and it works at the expense of clogging stuff up and I wouldn’t reuse the head gaskets personally but while you had the heads off you should take a straight edge and run it across both the heads and the block to test for plane. Clean everything thing out with garden hose and air pressure and also make sure the fan is wired correctly to the relay I thing 30 should be switched power (I don’t have schematics in front of me)