I need help, i got a guys 12v in the shop putting twins and other goodies on it for him, got everything put together, and now the thermostat wont open. I have tried 3 beand new cummins thermostats, i have even tested them in water out of the truck. The radiator and water pump work as they should, i ran it without a thermostat and had proper flow through everything. I have talked to a few other people at some other shops and i cant come up with anything. Please let me know if somebody has come across this, i am stumped and have nothing else to try Thanks.

 

If ya tested it in hot water and it worked then it should be good to go

make sure you are purged of air so the fluid is getting to it

stupid question but is it in correctly............I fixed one for a guy after he flushed the system and installed a new stat............same deal as you it just wouldnt open and he had it in upside down

 

X2 i was thinking the same thing

 

this might sound dumb but did you try replacing the radiator cap, cuz some times if they dont vent properly the can cause problems,

 

Got it finally, i retraced everything like 15 times, everything checked out fine, the temp sending unit failed, it looked like it was operating properly then once the motor stated getting some heat i it, the coil must od kept getting hot and would show that the motor was running hot, swaped in a new one and things are good to go, thanks guys.

 

good to hear man