Cooling system concerns (Page 1/1) jayg220 AUG 20, 03:20 PM Hello, I know there is a bunch of threads existing already about temp gauge and the cooling system. I have had my 87 GT for a few years now and when I initially got it the temp gauge seemed to work well and stayed between the 220 and 100 degree mark all the time and never really moved once it got there. Last summer the car seemed to run cool, then run hot at least according to the gauge. Sometimes the gauge would drop down slowly to 100 degrees and stay there, other times it would quickly jump up over 220. When I got the car the fan was wired on all the time, and I changed that back to work with the 235 degree switch. The fan cycles correctly and also works with the A/C. The gauge would move sometimes when you started it and this spring I did the wire modification to make sure that it did not peg on start-up. I could not get the wires to stretch far enough so I spliced in two extensions. I also broke the factory plug trying to swap the pins on the sender on the block. I ordered a new sender and pigtail from the Fiero store just to be safe and made sure to swap the wires when I spliced the new block end of the plug-in to replicate switching the wires inside the actual plug. These are butt-connected and heat shrinked. I ohmed out the new sender and got a reading of 205 degrees at idle on a hot day using the ohm-to-temperature chart thats been floating around this forum. The car seems to run cool enough, and rarely if ever does the cooling fan come on. Today I went to drive and its 65 degrees ambient temp and the gauge quickly shot up to 235 and would not move. The engine fan did not come on leading me to believe its all the gauge. I have the needle set on cold start somewhere in the middle of the thermometer symbol with the key on, with the key off it sits horizontally to the left. The car has a 195-degree thermostat in it, and when feeling the hose coming out of the thermostat housing it feels warm after idling for 5 or so mins. I did have an extra thermostat lying around today and just changed it. There is no change however I did notice a very slight drip coming out of the cap of the thermostat housing. (I imagine the o-ring on the cap finally tore when changing the T-stat.) I will order a new cap. When opening the T stat cap when the car is hot there is a hiss so I believe it is still building pressure. I will also order a thermal laser or thermometer gun to check the temp. I have read the thread on here about using the potentiometer to really dial in the gauge. While mechanically inclined, I am not the best with electronics when it comes to much more than basic stuff like splicing wires. I was just wondering if anyone thinks the problem is not in the gauge, and that maybe the car is running hot, or if I should try and find a good working used gauge. I have had the cluster out now a few times and would like to put this issue to bed. Otherwise, the car is sorted, rust-free, and has some nice upgrades. Thanks. Patrick AUG 20, 04:29 PM Running a scan and/or WinALDL would tell you the actual temperature of the engine. The ECU picks up the coolant temperature from the CTS, whereas the temperature gauge uses a different temperature sender. Doggo AUG 20, 04:36 PM About how quickly did it shoot up? There's been a few instances where my temp gauge will go from ~190 all the way up to the red line in a matter of maybe 5 seconds. One of them was even right after turning on the car lol. When I got the car I was skeptical of all the people on here saying that the temp gauge was the worst thing ever invented but as I've gotten to know my car, I can confirm that is in fact the case. Have you ever actually overheated? If not then I would say your gauge is probably pulling your leg. That's probably also the reason the feller before got spooked and wired the fan always on.