Brand new heater core, new thermostat and still crappy heat when at an idle. I have to be accelorating to get it to produce anything remotely warm. Any ideas? TIA!

 

Sounds like the vacuum line going to the heater control valve is leaking or weak.

 

Would you know specifically which vacuum line or the color? Ive done a million cores but theres a good chance something couldve gotten pinched!

 

Check your coolant/antifreeze level. If its low, your heater will act exactly like you described.

 

Water pump fins rusted off?

Ditch the heater control valve, plug the vacuum line and don't look back.

 

Thanks guys. If it had to do with the water pump, there would most likely be over heating issues right? Just seems logical to me...

 

Ditch the heater control valve as cruiser mentioned.

Bleed the cooling system again. On most vehicles, when you have the systems you described, there is an air pocket in a heater line somewhere.

When you accelerate from a stop, does it ever sound like there is water/liquid trickling behind the dash? If so, that's a good sign there is air in the system. Good luck!

 

If you get rid of the control valve, wouldn't you:

a. Lose the ability to modulate heat temperature on pre-97s?

b. Have straight engine heated water going in the heater core, even in the summer. Would it interfere/fight with the air conditioner evaporator, which is in the same box under the dash?

c. If it doesn't affect anything, why does it exist in the first place?

 

A) No, as the heat is controlled by a door, not the valve.

B)Yes you would have water flowing through the heater core. And no, it doesn't interfere with or reduce the effectiveness of the AC since the blend door is closed to the heater core side and open to the evaporator side.

C) It was a redundant feature not to open the valve for heat but to shut it for AC operation. Totally unnecessary.

D) If it didn't work, I wouldn't have been doing it for years in Arizona.......

 

thats one of the first things i ditched... heats like a dream now..

 

Some ppl use a brass gate valve in the area where the above picture depicts a plastic coupling. You would turn the valve to the open position to get flow thru the heater core and close it in summer months for A/C.

 

Great idea but not necessary.

 

I fall with Blue. I want control of hot water circulating in the cab. Period. Granted with good AC, (likely running in AZ), the heat from it may not be a big deal, but if it's hot and I'm not running the AC, the last thing I need is a little 210* radiator in the cab.

Chick, I'm no real help. Yours sounds like mine which is pretty week unless I'm climbing a good hill. I figure it's my 1/2 clogged core. New Mopar 195* stat. It's shurely primed. Interesting point on the fins. Djb posted a Pic of one pump that was just a flat disk! There might be a point where it will still push enough through the rad, but still not be full strength. I should check mine, even though it's just 12 years old.

Did you watch the lever on your valve while someone turned the heat on/off? (you can see it move). And last. It's a round plate like a throttle plate, that controls the water flow. I saw one once that had deposits so thick on the backside, that when fully open, only 1/2 of the pipe was open. (so the opening was more a "D" than an "O")

 

There's no heat coming in the cab either without the AC on. I actually rarely use AC. If there was any heat coming into the cab without it on, in Arizona, I wouldn't eliminate the valves like I do.

Those HCVs are troublesome and dangerous pieces of crap. They'll strand you, blow up in your face while working under the hood, and don't allow coolant to freely flow through the core ALWAYS and keep crud from building up in the core.

I'm telling you. It frickin works.

 

+1

Been HCV free for almost 2yrs now. 100% heat and a/c.