so i have an 87 iroc 305 which i recently just put headers and cat back exhaust on. I am currently in Nova Scotia and i just drove from Ontario some 2500 kms with no issues, then out of the blue my car starts running hot not overheating to the point of redlining it but quite a bit hotter than usual. (going solely on dash gauge). It will do it on idle and stop and go traffic fine on the highway (still a bit higher than normal). needed to crank my cabin heat and it would maintain it where i usually is. I have a single fan setup, and while idling i tested that the fan is not coming on as it gets upto and exceeds temp specs. Checked out the plug and fan relay and tested both and they are working fine. but found out the Green/White wire that is supposed to ground when temp is reached is not grounding. Also the what kind of temps should i be seeing on the top rad hose vs. Bottom rad hose at idle, there seems to be quite a difference of 60 - 80 deg. (laser heat detector used).. now i understand that with the new header setup it is possible it would run hotter but it did not until after this long trip which confuses me... im thinking it could be the coolant temp sensor?? because the green/ white appears to goto the ECM, then back to the coolant temp sensor?? is this the case?
just looking for some insight, gonna try a 160deg thermostat, could be with new headers car is just heating faster than it used to (read some Heat momentum post, good!!!) to see if that resolves the problem any other feedback would be great..

 

ok so i changed out my thermo to a 160 deg.. while i was doing that i found what would appear to be one of the leads to the coolant temp sensor was just dangling there not attatched but hard to tell, it appears it goes to a sensor on the BLOCK not head on the passenger side close to the firewall under the spark plugs (two rear on pass side)

 

Sensor in the block is the knock sensor, the one in the head is the fan switch.

 

yep thats what it was sensor in head is fan switch, got a plug end from canadian tire and soldered it to the broken wire and plugged in, all works good now