Im in the process of sorting out a few things on this super clean '84 GL I just picked up. Im concerned about the heater.

 

The heat output simply isnt what it should be. Coolant is topped of, and I have replaced the t-stat with a brand new OEM 192 degree unit. Motor is running great, and gets up to temp quick, and does not overheat.

 

The Heater controls seem to be working 100%. Controls from A/C and recirc, panel heat, floor heat, and defrost all work great, and blow strong. The heater temo control seems to work the valve 100%, from stop to stop.

 

But my heat is only luke warm.

 

The heater lines are hot. BOTH into and out of the cabin.

 

So....

 

 

My first thought is that the heater core is clogged, and it forcing the system to bypass.

 

Can somebody shed some light on the heater core temp valve? Is it known for being problematic? is there a way to service it?

 

Im going to try to back-flush the heater core this weekend, in hope of saving myself a heater core project this year.

 

Any suggestions otherwise?

 

Thanks!

 

swap the heater hoses around and check your heat.

thats what was the matter on my BRAT. seems those valves are a one way and you should try to reverse the flow from how it is now.

 

good luck report back.

Nice thought. Ill try that. The previous owner did have the motor our for headgaskets. maybe the lines got mixed up!

 

 

Thanks for the tip!

If the heater hose switch doesn't work, try blowing out the entire cooling system with some water pressure using a hose. Let it run for a good while, and to make it better run some scale remover for a good half-hour at idle before you try the hose. Then put in fresh anti-freeze and water. If it still doesn't work, it is probably a clogged heater core.

Your idea to back flush is right on. You can have the cleanest coolant in the world, but you never no how bad the last monkeys abused it. All it takes is a fine layer of silt on the core passages and there goes your heat transfer. Just did mine for the same reason, and I'm cookin' now!

Nice wagon! Thats a beauty! A washing machine hose fits on the heater lines perfect. Halve one and you get one to the hose and one to your collection bucket.

Edited November 13, 201015 yr by Yo'J

Just an update....

 

 

Ive got heat! And from what I can tell, the lines were not backwards. I think the core was plugged just enough to force it into bypass, or the bypass vale was jambed up internally.

 

I back-flushed it with the hose for a bit, all the while cranking the heater valve from cold to hot multiple times. Then did the same from the other direction.

 

Then, I hooked it all back up and gave the entire coolant system a chemical flush.

 

Then a rinse....

 

And back to a 50% coolant/distilled water mix.

 

And she's pumpin' out lots of heat!

 

Thanks for the help guys!