[RyanU]

ok heres the deal. after we got my motor back in everything was fine for a while. then i noticed my coolant temp wasnt coming up one day. so i got out and beat on the thermostat housing, gave the truck a little throttle and the temp shot up to 210, heater started putting out warm air and then temp dropped back to about 170 or so where it usually runs. then if you kill the truck for a while or let it idle for about 10 min the heat goes cold again.

i replaced both thermostats and still having the same problem. anyone have any ideas to try and fix this?

 

[deepsouth]

Sounds like you have air trapped in the block. Have you tried letting it warm up with the radiator cap off? It make burp a little coolant, but it may let the air out. Then put the cap on with it running, and top off with the coolant overflow tank.