spudf16

I replaced the temp sensor in the intake of my all stock '85 after a tunerpro RT scan told me it was reading about 40 degrees cooler than the dash temp (200 on the dash read 160 at the sensor). I also changed the thermostat to a 180 degree at the same time. The combo worked and scanned great for 2 days.
Now, the temp slowly and steadily rises to 228 degrees on the dash while the tunerpro scan reads 180-188 degrees for coolant temp. Then the main fan comes on and the temp readings stay within about 8 degrees of those above. In other words, the dash temp stays in the 220s and the fan doesn't shut off until I shut off the car.
The upper hose is warm/hot, the radiator cap is barely warm and the air being sucked in by the fan is cool. I'm pretty sure the car is running cool but I don't know why the fan is coming on if the temp sensor to the ecm is in the 180-188 range. Thoughts?

1stL98

i had a similar situation on my 85.it was an air pocket in the system causing the difference in temps.i removed the t stat poured water into the block.then reinstalled the stat.filled radiator after the thermostat opened,i raised th idle with my hand and topped it off.it was normal after that.hope this helps

spudf16

I'll give it a shot this weekend, thanks.

cwyates4

shoot the upper hose with an infared to see where that temp actually is!

spudf16

Good call. Do you think it would be accurate to shoot the side of the block where the dash sensor is?

spudf16

After top offs and test drives, it turned out the 180 degree thermostat I installed failed after the second day I installed it and was blocking flow to/through the radiator. I reinstalled the 195 degree thermostat and it works normally now.
Apparently it's hard to make a thermostat that lasts more than 2 days...