Is there a valve that controls the flow of coolant to the heater core? I am trying to flush the cooling system and I cannot get water to flow through the core. The Temp control is to heat. I left it there yesterday while driving but had the blower and dash control off when the truck was shut off. I started the truck today with the air control to "Floor" and the blower on. It still does not allow water through.If there is a heater control valve, can it be manually opened? I saw a schematic of the vacuum lines on another post and it looks like damper doors control the temp.

 

I don't know what year your truck is, but there isn't a control valve on my 85 or 86. Sounds like you have a seriously plugged up core.

Good news is, at least on the '83-'86, the heater cores are really easy to replace. Don't know about the newer years.

 

Newer ones are too -- just need a nutdriver of the right sort; pull the glove compartment and then remove the black panel under it.
Unhook the hoses from the front side, mop up the spilled coolant and just pull the core out, into the cab. 1/2 hour replacement, easy.

 

Sounds like the same procedure then. I wish all heater cores were that easy. I had an '86 Volvo 760 once. Nice car, but it was built around the heater core.

 

Change one in an AMC Eagle and you'll beg to do the Volvo one again-

 

Haaaa, I found the pic of that horrible mess:



One thing to the Swede's credit though, look at the length of wiring. I didn't have to unplug anything, just set it aside. American cars make the wire just long enough to reach the component, then cut 1/8" off.

 

I'll have to take your word on that one, I never even see Eagles anymore. Kind of surprising though, they were a very popular vehicle in their day.

From what I understand my Volvo was a PITA because the 760's were climate control. The 740 would have been a typical job from what I was told.

That new core was $$$$ too!

 

Yeah, so predictable, gotta love it. I'll bet it's even worse recently, with how expensive copper has become.

To the OP - try removing both hoses right at the heater core, and then hooking a short piece of hose up to the inlet and connect a garden hose to it, see if that direct pressure does anything. If not, put the hose on the _outlet_, so as to backward flush it. If that gets it, then you have some contaminant in your coolant and a filter may be in order. If not, yeah, it's new core time.

 

On a 64 the heater control valve is on the passenger side inner fender, Make sure the heater hoses are installed correctly from the water pump or it won't work.

Heater cores for 64 is an orphan part, when they (were) available they were almost 300 bucks or something stupid like that. They can be repaired by a radiator shop.

 

My apologies on providing incomplete information. The truck in question is a 94 7.3 n/a. My other truck is a 64 with a 292 and I was able to flush all kinds of brown stuff from its heater core. This one must be plugged bad.

Now I know there is not valve I will put 15 or 20 lb of air pressure on it to see if that loosens it up. If not I will pull the core and work on it or replace it. The coolant I have retrieved so far has been clean, real clean. The engine is running hot so the PO may have flushed the system trying to solve the issue. I am going to do a 3 day chemical flush and want the heater core to be flushed at the same time.

I am going to Ford and get a new thermostat in the morning. I live in South Texas and it will be getting hot soon. I want the cooling systems to be in good shape, including the little used heater.

 

Blasted the core with 20 lbs of air and she coughed up a rust ball and the water is flowing again.

New thermostat is in and she is running cool again.

 

Good job!