So I baught a 1986 B2000 runs good, but on the way home noticed temp gauge in dash wasn’t working. So new thermostat, radiator, temp sensor (the one below thermostat housing) still in/op gauge and cold lower hose. My buddy and I put on a Weber carb and header, when doing that he noticed that the head was new and everything come apart really easy. We were going to change the timing belt and water pump but both were new as well. With the radiator cap off you can see that the coolant is circulating. So I drove it home 40 miles and the lower hose was still cool to the touch. Not warm at all, upper hose and top of radiator seemed to be normal temps. I could touch and hold them for a few seconds before becoming uncomfortable. Any help is appreciated.

 

How long did you drive it for?
What brand of Thermostat did you fit?
You could try removing the thermostat, sealing up the housing flange, bleed it up, go for a drive & recheck the hoses.

 

Check "METER" fuse. If you ground that sender wire for a half-second with ignition in "run" position, does the needle deflect up ???


Bleed ALL the air out of the coolant system. Jack up front of truck or park on steep uphill. take off radiator cap, turn on heater and run engine 20 minutes, topping up with coolant as necessary. The replace cap, lower, etc.