GoldenP21

Temp will actually read a little below normal as long as you keep it under 50mph. As soon as you push the car a little the temp will shoot up to almost the red then drop back down. While this is happening the car will idle higher. Also when you turn on the heat it comes out cold until it hits the red and starts to drop. Need a new thermostat ubt is that it?Any ideas?

ckyguy68

You might want to try burping your cooling system. It could have air bubbles in it. My car would always do that from losing fluid through a bad cap. Once the coolant would get to a certain level the thermostat would start opening and closing causing the heat to stop blowing. Whenever i topped it off the problem would go away...

GoldenP21

I thought it was exactly what you said. I burped and topped it and no change.

projectresto83

You could replace the thermostat and see what happens.

GoldenP21

which thermostat should I use?

mjr46

195..stock and do you have good heat at idle..if not try bleeding cooling system again until you have heat

brentloftis

Subscribing:

I have my work horse 83 Ford that does a similar problem, my temp jumps after a miles at the 45 - 50 mph area and backs off as soon as I slow down. I did the thermostat with no change.... I am at the point of thinking a blockage in the radiator just have not got around to clearing / changing it, hardly ever get over 40 in it anyway.

GoldenP21

I have good heat at idle but if I get on it, it rises at a scary rate.

brentloftis

The gauge rises very fast? I can not recall where I heard this before and did a quick search to try and find it but no luck, but I seem to remember a issue with Fords and the gauge of the wiring for the head light switch, something like incorrect resistance or something that would cause the temp gauge to"short" (wrong word for it I am sure) but get incorrect information and show hot. I hope someone else remembers this or has at least heard of it before.... that way I am not crazy

Again fuzzy memory but I think after the was engine warmed up, you could turn the engine off and headlights on and watch the temp climb rapidly showing the false positive....

87greyghost

how long have you had it. When i got my 87 it was doing something similar whenever id get on it the temp would creep up on me till it got really close to the red line. I recently rebuilt the top end in it and found out it was bored .040 over. I flushed the system and put a stock radiator back in it. A buddy of mine told me that it being boredwas the problem so i think im going to have to get an all aluminum radiator.