Heat only works when vehicle is moving...Why? [Archive] - The Chrysler Minivan Fan Club Forums

: Heat only works when vehicle is moving...Why?



BlackOnBlackCobra96
11-23-2008, 08:33 AM
I checked the coolant thinking that there wasn't enough to go to the heater core. It did seem a little low (maybe a slow leak), but I still have the problem even after the van is topped off. This is for my '01 Voyager. Anyone have thoughts?

Scott Loveall
11-23-2008, 09:01 AM
bad water pump......not pushing enough fluid? Just a thought.

blupupher
11-23-2008, 11:15 AM
Bad thermostat, bad/leaking vacuum line (blend door not opening fully at idle), bad water pump, partially clogged heater core (I would check in that order, and this is given that there is the correct amount of coolant in it).

BlackOnBlackCobra96
11-30-2008, 12:57 PM
Okay, so I swapped out the thermostat and still no luck. The upper radiator tube doesn't get hot. How would I check the water pump? Is there a way to run a couple of wires to it from the battery to test it?

sideburns2009
11-30-2008, 05:16 PM
Its possible that its got some trapped air in the cooling system somewhere. When all else fails you can drive it up on some ramps or jack it up to the the front end as high as possible and let it run without the radiator cap til it warms up, this is suppose to push the air to the top and out of the radiator, then top it off. My old auto teacher taught me this but I never tried it...didn't ever get the chance.

Sunvanse
11-30-2008, 09:40 PM
Your sig. states 190K+ miles. Is the water pump original? The vanes may have disintegrated by now. The pump is belt driven, not electric.

blupupher
11-30-2008, 10:38 PM
I don't know of any easy way to check the waterpump. More a process of elimination.
It is possible the thermostat is bad (did you check it before installing it by putting it in some almost boiling water? I have had 2 "bad" new thermostats (1st one installed, 2nd one checked before installation)). Was it put in correctly?
If the thermostat is good, coolant full, heater core good, then it is the water pump.

rabbler
11-30-2008, 11:09 PM
Does your temp gauge rise approx 1/2 way. If so your thermostat is fine.
It's possible you have an air lock. I would think if your water pump is bad you would have an overheat condition.
Does your van have rear heat? Wen I got my van back from the dealer after having the rear heater hoses replaced there was a big air pocket preventing heat.
I pinched off the hoses to the front heater core (vice grips) to force flow to the rear.
A big air bubble came out while revving the engine. (1500 rpm for 5-7 minutes)
I had to add almost a whole gallon of coolant to the rad and overflow tank.

sideburns2009
12-01-2008, 12:39 AM
Does your temp gauge rise approx 1/2 way. If so your thermostat is fine.
It's possible you have an air lock. I would think if your water pump is bad you would have an overheat condition.
Does your van have rear heat? Wen I got my van back from the dealer after having the rear heater hoses replaced there was a big air pocket preventing heat.
I pinched off the hoses to the front heater core (vice grips) to force flow to the rear.
A big air bubble came out while revving the engine. (1500 rpm for 5-7 minutes)
I had to add almost a whole gallon of coolant to the rad and overflow tank.
Thats what I was suggesting. Air can take a big toll on your heat.

BlackOnBlackCobra96
12-01-2008, 10:50 AM
The thermostat goes to the half way point, so that should be good. The vehicle hasn't overheated, but it's been really cold so I don't know if I can rely upon that test. Is water pump something that can be tested at an Autozone, Pep Boys, etc. type place like an alternator or starter? BTW, the van doesn't have rear heat.

AzTraveller
12-01-2008, 11:06 AM
OK, the van is NOT overheating.
When you followed the recommendations of the team, here about burping the cooling system, did you have the heater turned on ? CAP OFF, reving the engine, heater ON, should get ANY bubbles out. The last thing you may wish to do is look at the heater control valve. It is on one of the hoses on the firewall heading to the heater core. Touch the hose above it and see if it is getting HOT, not warm, but HOT. If it's warm, make a mental note where the little lever is (towards the vacuum diaphram, or away. Turn the heat OFF, look at it again, to see which way it is now. See if you can manually move the lever on it. Is the hose still warm, or cold, or hot?

If it's toward the vacuum diaphram, remove the vacuum hose, see if it moves back. Also see if you're getting vacuum (put your finger against the hose end). Turn the control ON, see if you get vacuum at the hose. Reconnect it.

Let us know what you've found.

DaveKG55
12-01-2008, 05:31 PM
OK, the van is NOT overheating.
The last thing you may wish to do is look at the heater control valve. It is on one of the hoses on the firewall heading to the heater core. Touch the hose above it and see if it is getting HOT, not warm, but HOT. If it's warm, make a mental note where the little lever is (towards the vacuum diaphram, or away. Turn the heat OFF, look at it again, to see which way it is now. See if you can manually move the lever on it. Is the hose still warm, or cold, or hot?

If it's toward the vacuum diaphram, remove the vacuum hose, see if it moves back. Also see if you're getting vacuum (put your finger against the hose end). Turn the control ON, see if you get vacuum at the hose. Reconnect it.

Let us know what you've found.

I don't mean to hijack this thread but my van has no heat and I strongly suspect the servo-driven blend door is not moving (I think the linkage is broken or disconnected ... I have a separate thread on the subject). I am confused when you speak of the "heater control valve", "the little lever", and a "vacuum diaphram". My 4th gen van has none of these with regards to the HVAC system, or so that's what I believe. Are you certain of these things or am I (or you) mistakenly referring to a previous generation van? Can you clarify some? :ask_wsign

Thanks...

badbaldtexan
10-24-2011, 02:57 PM
If your van is like mine, it has a heater control valve inline in the heater hose but it is neither vacuum or electrically operated. It is just a one way valve. If anyone has changed one of these, could you please tell me which way the flow is? Broke mine and could not see the arrow. Thanks..

sloan987
10-24-2011, 03:55 PM
A possible problem with not enough coolant in the system, could be a bad radiator cap.