heat has mechanic stumped

[Worktruck]

Long story short is my truck has a new thermostat, new heater core, new 4 way heater valve, good water pump, and good blend door and actuator, but still no heat. It just blows cold air all the time. There seems to be no reason that the heat shouldn't be working, and my mechanic can't think of one. Anyone here have any ideas?

 

[Mickey Bitsko]

Hmmm.. kinda sounds like you have an air block in/or going in the core. Have driven the truck to operating temp.While cycling the heater and let the truck cool and repeat with your over flow filled to the "cold level" ? Sometimes it will push all the air out and make the cooling system completely void of air.
Kinda went the long way with that expanation.

 

[shane96ranger]

I would try and hook a garden hose up to the core and visually see if it flows OK. I had a new core that had BARELY any flow in my Explorer.

 

[Mickey Bitsko]

I would try and hook a garden hose up to the core and visually see if it flows OK. I had a new core that had BARELY any flow in my Explorer.

Thats a good idea..

 

[RonD]

What engine what year??

Could be a few things but engine and year matter alot, and does it have AC?

 

[kimcrwbr1]

Pull the heater hoses off of the motor and look at the fittings the one on my thermostat housing wass almost all the way plugged with rust on my 2.8. Also the best way I found to burp the system is put a flushing tee in the heater hose that goes to the thermostat hold it above the radiator and pour coolant in until it runs out the radiator cap.

 

[kimcrwbr1]

http://www.ebay.com/itm/Prestone-Antifreeze-Coolant-Flush-N-Fill-Kit-59060-/160564730785?hash=item2562675ba1:m:m5WsJ5Vzud1VBEekv_lwvWg&vxp=mtr

 

[adsm08]

You don't even need to pull the hoses off. If the heater core is plugged one hose will be hot, one will be cool after the engine warms up.

Also, keep in mind that "new" does not equal "good". I'd go back and look at that stupid bypass valve. I'd look at it right up until it goes into the trash can, then I'd forget it ever existed.

 

[Mark_88]

You don't even need to pull the hoses off. If the heater core is plugged one hose will be hot, one will be cool after the engine warms up.

Also, keep in mind that "new" does not equal "good". I'd go back and look at that stupid bypass valve. I'd look at it right up until it goes into the trash can, then I'd forget it ever existed.

Hmmmm...I think I should find out if my 96 has such an animal and see about getting rid of it...there is something on the front of the engine that my 88 didn't have and it has wires...sits on the connection coming off the water pump and I was thinking it was made of plastic...if that's a bypass then I'm going to see about removing it...