I was driving my '89 F150 4wd w/302 over the weekend. It's at my cabin so I only get to drive it a few times per month. Anyway, it was pretty cool in Upper Michigan and it was hard to get a lot of heat.

We did have heat and the longer we drove it the hotter it got. My temp gauge would always stay pretty low though.

Is this an issue with the thermostat? I was just going to buy one and the gasket. Somewhere around $5 at advanced auto.

Are there any tricks I need to know about changing it?

 

The gauges aren't all that accurate, chances are the gauge temp sensor is going bad. If you are getting heat then the t-stat is working like it should be.

 

might be time for a fluid flush and fill, anti-freeze does go bad, and you dont know how many times it has been diluted down with water or to much anti-freeze and not enough water.

 

We figured that the thermostat is open all the time...causing the antifreeze to constantly be moving through the system and radiator. Therefore making it not get as hot.

The person that owned it before me had the coolant watered down. I have now got it almost to 50/50. I had to drain it and put the pure in and we tested it. The coolant is fine. Both of the temp sensors are new.

It gets heat...just not that much. In the summer it would get a LOT of heat. I realize that's summer but it should still get to temp when it's cold. Or, do these trucks just not get hot when it's cold?

 

My first 87 didn't have a thermostat in it . Stock thermostat is 195 degrees. Lots of people put lower thermostats in, or remove them completely. If you bought the truck and don't know you wold be advised to open her up and stick in a new stock 195 degree thermostat.

To my knowledge there is no performance benefit of a lower rating thermostat, stick with the 195 degree. A hot motor is more efficient.

 

The gauges are mostly for decoration.

 

195 degree stat is the way to go. Also, depending on what name brand temperature gauge sensor you get determines how little or how far the gauge moves.