heater and temp gauge problem

O

ottoschmidt

Member
hello i need help,
i have a stock 1940 239 flathead truck 1.5 ton all rebuilt . For two winter seasons now i would open the heater shut-off valve and have incredible heat in the cab .So the temperature has dropped into the twenties here in Pittsburgh and i take it out for my bi-weekly ride . i drove it for 40 minutes uphill and down hill and let it idle for an additional half hour . my temperature gauge never rose from cold to warm(pegged on C) and my heater is blowing ice cold air . never warming up at all . i disconnected the heater hose to the heater core on the firewall while the truck is running and it is dry not even a drop.Disconnected the other side to the heater core and not a drop to be found . the radiator is full.the shut off valve is turned on. the thermostats from C@G only 3 years old .I put my hands on the motor after an hour running and its not very hot . the bottom rad hose where the heater hose connects to is not very hot either.there is no pressure to the heater hose obviously . What going on guys ?
Best Regards
 
Thermostats don't seem to be working properly. Install a pair of 180 degree thermostats and it should warm up nicely. Report back to us.
 
Gosh, this is a tricky one. Since it worked before, it is not plumbed up wrong, yet there is air in the heater line. Generally they like the water going in the bottom of the heater core, and exit from the top to push air out of the system. Again, yours worked before , but not now ? how about a heat gun to see where the heat stops ? Is the off/ on valve actually threading in and out? I'm stumped
 
check the thermostats are installed correctly and havent migrated or rolled had no end of drama till i figured it out there are several ways to keep them in spot depends what suits you
 
thanks guys ,im going to have to remove the thermostats and do the boiling water test .Yes i have heard of them becoming unseated before .This is very strange .
 
I think this is the first thread I have ever seen about a flathead running too cold.

Stick around long enough and you'll see everything!
 
what eng are we talking about as thermostat migration is well know in all but the 8BA series due to the way their mounted as the original hoses had a lip inside them that kept the thermo in place yet to find a replacement with this feature my personal fix was stainless pipes jammed down on the stats and clamped in place [polished stainless looks cool ] there are several threads on this subject on here
 
well problem found,the thermostat on the passenger side moved out of postion and was standing up instead of laying flat .this kept the hot water from entering the heater hose .unusual ...
 
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