Any auto mechanics-heating question

[forgop]

So, my wife's van (2005 Dodge Grand Caravan) isn't heating when it warms up in the driveway. You can let it run for 30 minutes in the driveway and it won't remove the frost or anything, even though the temperature is high enough to begin warming from the engine. Once you start driving down the road, you notice after a minute or two, the cold air that was blowing is now as toasty as can be. Any suggestions why we're not heating while it's in park in the driveway but works fine once you get on the road?

[GolfNut]

Could be water pump going south on you. Could also be partially plugged radiator or heater core.

Also, not sure about that van, but some rigs have a vacuum actuated heater valve that when triggered diverts the flow to the heater core.

[forgop]

Originally Posted by GolfNut

Could be water pump going south on you. Could also be partially plugged radiator or heater core.

If it matters, I did have to fill up the radiator earlier in the summer at one point. Engine damn near overheated and it wasn't that low really and not even that hot out.

[thebayratt]

Originally Posted by GolfNut

Also, not sure about that van, but some rigs have a vacuum actuated heater valve that when triggered diverts the flow to the heater core.

My Dodge Ram does that at odd times. Its a vacuum valve thats screwy....
I can go down the road with just the "vent" on and all the sudden, it goes to the defrost air flow. I let off the gas or take off the cruise control (also vacuum actuated) and it goes back to "vent".

That or the thermostat is sticking... Get a "failsafe" thermostat. If the fail, they fail in the open position; so not to overheat your engine.


Look and see if your water pump is dripping any water out of the bottom of it. When they go bad there is a "weap" hole that water comes out. I had to change mine last summer bc of this.

Check in the engine compartment for leaking antifreeze or coolant...if air gets into system sometimes you'll get a case of it not being able to pressurize the system enough while at idle but will when rpm's reach a certain level while driving. You'll generally hear a gurgling sound while running the heater too...

[GolfNut]

I hate to throw so many things out there, but check the vacuum lines for the blend door to make sure it is working properly.

Also, do you notice a temp drop when you come to a stop? (is there a dash gauge?) A stuck open thermostat will give you those same symptoms.

[SvilleKid]

This is probably simple, not complicated. The cooling system is either efficient enough that, while at idle, the engine isn't heating up enough to open the thermostat, or the thermostat may be sticking closed until higher temperatures. I'd bet the thermostat is at least 215 degrees.

[Sled Dog]

Throw another vote for thermostat.... that's exactly what it sounds like.

[replicant_argent]

Stat, control/blend problem (maybe), partially plugged core, water pump vane erosion, a few possibilities.
when it sits at idle, can you get to the return line from the heater core? if it is warm, you can isolate it to behind the firewall, whether a heater core, or a HVAC problem, rather than pump/radiator/stat/etc.

I would toss a stat in first, as it is cheap, easy, and if you haven't done one in a couple years, might as well. Especially since you had a cooling problem recently, and it may have boogered the stat.

[Blueface]

Thermostat vote here.

[jmsremax]

I had a similiar issue with my first car and my problem was the thermostat wasn't closing. I think I paid $15 to get a new one at Autozone. Hopefully this is the case with you.

[68TriShield]

Low coolant level again or bad head gasket/cracked cylinder head.
Which could be why you lost coolant in the first place.

[Blueface]

Originally Posted by 68TriShield

Low coolant level again or bad head gasket/cracked cylinder head.
Which could be why you lost coolant in the first place.

Oops.
Missed the "coolant" part.

[jmsremax]

Originally Posted by jmsremax

I had a similiar issue with my first car and my problem was the thermostat wasn't closing. I think I paid $15 to get a new one at Autozone. Hopefully this is the case with you.

I meant to say it wasn't opening

[357]

Originally Posted by Blueface

Thermostat vote here.

Disclaimer: I am not a mechanic. I have however done a lot of work on my own cars out of financial necessity.

A bad thermostat is most likely and is cheap/easy to replace. <$10 usually. It sounds to me like it is sticking closed and requiring a hotter temp (more pressure) to open it. I recently had the exact opposite issue. My thermostat was stuck open and my engine often wouldn't reach the proper temp. Heat from the vents was never warm enough. $8 and 20 min later it was fixed.

Other cheap fix could be a radiator cap. Again under $10 and sometimes fixes cooling issues, depending on the type of system in your vehicle.

Obviously check for leaks in the coolant system, hoses, radiator, overflow resevoir, etc. If none are found, but you have to add coolant again, check your oil. If you find antifreeze (or smell it) in the oil you could be losing coolant due to a bad head gasket. (Big money and PITA).

IMO, if the water pump was bad you'd know it. Usually they fail catostrophically; as in they bite into the block and the pully snaps off due to pressure from the belt. I've had this happen twice. Once each on two different cars once they got around 160K miles. They also tend to make noise before they fail.

Heater cores don't fail often. When they due, it is usually because they spring a leak and fill your floorboards with coolant. I've only had to replace one once; it failed to get hot and yet was not leaking. I believe it was plugged.

[T.G]

Awww, come on guys, it's so simple maybe you need a refresher course. It's all ball bearings nowadays. Now you prepare that Fetzer valve with some 3-in-1 oil and some gauze pads, and I'm gonna need 'bout ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State.

[forgop]

Thanks for the responses thus far....gonna replace the thermostat tonight and see how that goes.

I wonder if the guy from the car parts has the exact thermostat from any of those parts that looks like it has a place where hoses could go?

[pektel]

Auxillary coolant pump is my guess. And I'm pretty confident in that guess. Since it gets to the proper engine temp, I doubt it's a thermostat. But I could be wrong.

Shouldn't be too expensive. Around $300 with labor at a dealer I wager.

[pektel]

Originally Posted by pektel

Auxillary coolant pump is my guess. And I'm pretty confident in that guess. Since it gets to the proper engine temp, I doubt it's a thermostat. But I could be wrong.

Shouldn't be too expensive. Around $300 with labor at a dealer I wager.

Forgot to add the same disclaimer as 357 up there. I am not a mechanic. But do work on my own cars. And I'd rather not pay someone to do something that I could do on my own. Time allowing, that is.

[T.G]

http://www.youtube.com/watch?v=OSBmo8F7N-E