The heater wasn't working so I looked at all the possibilities (felt the heater hoses under-hood, checked the flap doors, felt the hoses behind the heater core and only the inlet was hot.) Baffled, I figured I would start with a new heater bi-pass valve and do a quick flush.

Disconnect here for the direct inlet flush with the garden hose

This is the heater bipass valve I started with new

This comes from the return line of the core, remove hose here and the front hose goes here temporarily, you can new see the new bipass valve on the left (front of truck). If you don't use the temporary front hose here the coolant will flow directly onto your cops and boots.

This front hose connects to the return outlet temporarily and drape it around the oil fill tube so you don't get water on the cops. You need to put it back last because the steel pipe it connects to is where you need to bleed the air at the manifold. The garden hose goes in the end of this to back-flush the core.

This is the front hose again, it goes on the return fitting in the back temporarily and it used for the return back-flush with the garden water hose


I don't know what I did (because the old bipass valve seemed to be OK and the water wasn't very dirty) but the heater works great now so I can't complain.

 

Thx Brent, mine went bad and I had a similar issue. Easy and inexpensive fix, great pics.

 

Thanks, still working on it, you might want to go back.

 

Glad its all working again! Even if the valve seem to work it may have been hanging up when hot and with pressure in it.

 

OK, I was thinking it wasn't working most of the time because I did have heat one time, also when I had the AC evacuated and charged lately the garage had it on max AC which I had never used before.

 

I notice 2 things.
First, it seems rusty water leaked from the return line going into the heads ?
Second, is that a crack right behind the hose ?

 

That is the inlet line for the core and its coming out of the intake manifold. The rust stain has been there for a year (before the flush I did a thread on). My water is crystal clear and when I backflushed the heater core just a little dirt came out for about a second and then it ran clear. I run antifreeze 50/50.

Not a crack, pictures can be deceiving.

That pipe is where to burp the system from.

 

update; Another way to do the flush is to attach a piece of heater hose to that back T fitting and remove the hose from the front of the heater bypass valve. Put the garden hose to the piece of hose you had lying around for the backflush and put it directly on the bypass valve for the direct flush, then use the disconnected hose end in front of the valve to burp the system when you refill the rad tank.

 

Wonder if I should do this before I move to VA...

 

It doesn't take very long.

 

But.. how would a heater core clog up ? Only thing I can see happen is if you use hard water instead of distilled, or somewhere else in your system you have parts coming loose floating in your cooling system.
Really saying if you do a regular flush and coolant change with correct coolant/distilled water mix, you won't have any clogging.

 

Thanks for the write up subscribing in case I ever need it. One question, see that little thing in the upper right of this photo with the light green dial **** on it - what is it? Says EVAP something on the tag, but still don't get exactly what it is or what it does?

 

It's a valve for the evaporative system.
It basically opens up when the engine runs and let the vacuum of the engine pull out any fuel fumes that are stored in the charcoal canister.
When the engine does not run it is closed and all fumes coming from your fuel tank will store in the charcoal canister.

There is another valve on the charcoal canister (I think it's a solenoid) that also opens and closes to let air in /out.
I am sure other people here can explain it better. These evap systems are basically the same on any modern car. Store in a charcoal canister, remove and burn it in the engine when the engine runs.


I think the green **** is to test the evap system.

 

Yep it's something they came up with at least 30 years ago and about the time they came up with the gas filler hose that traps any fumes............big waste of time and money if you ask me.

 

Easily. Look at a core after 100 k miles and you will see a lot of junk in there if they never flushed the coolant (like mine when I bought it). Those passages are tiny in there and I guess the junk comes from the insides of the hoses, etc. Look at water that hasn't been flushed for years and the inside of radiator tanks. My tank is still dirty inside from when I bought it.