In my 1996 F150 (6 cyl, 300 engine) I recently had the thermostat housing and water pump changed to cure a leak in the pipes attached to them that went to the heater. Now I have no heat and the temperature gauge barely climbs up into the normal range. Before, the gauge would go about three quarters of the way over and then drop back to half way as the engine was warming up and I had good heat. Does it make a difference which heater hose is connected to which pipe from the engine? Both of the heater hoses on this truck are the same size. The thermostat was changed along with the housing. Is the thermostat hanging open or is there something else I should be looking at? Any ideas??

 

Sounds to me like the thermostat is stuck open. I had those exact symptoms with a stuck thermostat...

 

Either that or they put in a 160 or left it out altogether.

 

A mechanic friend said he has seen the failure rate as high as fifty percent with thermostats straight out of the box. Next step, change the thermostat. Thanks guys..

 

yea check that thermostat, did you purge the cooling system? there possibly could be an air bubble in the cooling system

 

They may have installed the thermostat in backwards. It seems silly to suggest, but this did happen to me on my 94 F-150.

 

Air bubble was mentioned and the backward thermostat too. Is there a correct inlet and outlet hose connection to the engine since both hoses are the same size? One hose has a "T" connection with a smaller hose that connects to the radiator just below the cap and the other one goes straight to the heater core. Just curious, some models have one hose smaller than the other so they can't be switched. Thanks for the replies.

 

Yes, flow direction to the heater core does matter, they are not uni-directional.
However, that does not/would not explain the motor not coming up to temp, that would be T-stat.

Personally, I would get a real gauge and go by it on the water temp, and hook the heater hoses up according to factory ... Sorry, Don't know what hose is what on Gassers, on the Diesels the heater connection closest to the fender is the Supply (hot).

-Enjoy
fh : )_~