Intermittent heat inside

Intermittent heat inside

Postby romeroom [OP] » January 8th 2013, 8:13am

2002 Astro AWD with rear heat/air

After running the van for more than a half hour, at idle, the air begins to come out lukewarm, even though the climate control is all the way up, so I should be experiencing very hot air. While idling, I rev up the engine and the air gets a lot warmer, bordering on hot. This is with outside temp at 31 F. Also, the rear heat blows cold air now--no noticeable warm air coming out.

The service engine line came on and the code had to do with the cooling system; I will check it again tomorrow and tell you specifically what the code is.

Suggestions?
'2002 Astro LS, AWD, 41k miles, "W" VIN
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Re: Intermittent heat inside

Postby DorisTheFunkasaurus » January 8th 2013, 3:16pm

My intermittent heat problem was much the same, and I finally figured out that when my coolant level would drop my heat would start acting up. As soon as I topped off my coolant again, heat would be fine.

I realize this is pretty simplistic- I'm learning about this stuff the hard way. I had already replaced my thermostat and probably need to flush my heater core... but the coolant level was my smoking gun. I just found out I had a very leaky intake, which explains why I've been going through so much coolant.
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Re: Intermittent heat inside

Postby tedanderson » January 10th 2013, 1:06am

X2 on the coolant level. This had been an ongoing problem for a couple of years on another vehicle that I own. I pulled the cabin air filter and it got better for a while but once I was able and willing to bite the bullet and get that special red antifreeze, the heat became hotter than a summer day. :banana:
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Re: Intermittent heat inside

Postby redfury » January 10th 2013, 4:43am

Another thing to look at is the vacuum line going to the heater valve. It shouldn't be drawing any vacuum at all when the heat is on. When you put the engine under load, the vacuum decreases and the valve will open up again. I had this problem recently due to having the wrong sized vacuum line on the valve in addition to having the hose connected to the wrong vacuum source. It should be connected to the firewall connection and be the only connection. It's usually the lower of the two. The other vacuum connection should have the engine vacuum and the vacuum ball connected to it as well as the rear heat connection if you have rear heat.
A temporary fix usually becomes a permanent solution, therefore it does not exist.
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Re: Intermittent heat inside

Postby Spider'sSafari » January 10th 2013, 5:51pm

I just help my brother with this issue on his Chrysler Caravan w/rear heat. He had to replace the water pump over the summer and never really purged the system, causing air to cavitate in the hight spots in the heater cores when under pressure once it heats up. The air left in the system gets hot too and rises to the highest spot in the system or top of the heater cores, because there is room at the bottom of core for coolant to flow across and back to engine so only part of the core has hot coolant in them.

Park the van front end high or jack up slightly, When cold, remove the radiator cap and start engine, TURN heater selectors front/rear to HOT and fans on LOW, Let it run to normal temps. reving it up slightly every minute or so.
Once the thermostat opens, You should see air bubbles come out at fill neck opening and the coolant level go down. Slowly add coolant as the level goes down to keep it at the top of the neck and any air out of the radiator.
This can take 15 min to 30 min for all the air to be pushed out of the heater cores and to the high spot of the fill neck. Reving it up a little helps increase flow and push out air, but don't rev up to high other wise the coolant will overflow out the fill neck. As long as the radiator cap is off the system, it will NOT build pressure and will push all the air out n slowly find it's way to the fill neck and out. Once the coolant level stops going down n no bubbles, install radiator cap n top off coolant resovoir.
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Re: Intermittent heat inside

Postby romeroom [OP] » January 12th 2013, 6:24am

Thank you for all the replies. I will be exploring your suggestions in the next few days.

The CEL code is: P0128 - Powertrain: Coolant Thermostat.

Van should have a coolant flush done. Any quick suggestions on this? Never done one.
'2002 Astro LS, AWD, 41k miles, "W" VIN
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Re: Intermittent heat inside

Postby redfury » January 12th 2013, 2:46pm

sounds like you need a new thermostat. As far as the flush goes, just get the flush kit and cut the heater core hose and put it in. Easy as that. You use the supplied connector that regulates the flow of water into the system. Once you've flushed the system out, you realistically should drain everything ( pull the lower radiator hose, or petcock on the radiator if you have one ) and then fill it up with a 50/50 mix of antifreeze and distilled water. The distilled water is used to prevent scale from forming inside the cooling system from hard water minerals that come out of your tap.
A temporary fix usually becomes a permanent solution, therefore it does not exist.
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Re: Intermittent heat inside

Postby Ragenme » January 12th 2013, 3:21pm

I was reading this to see if I could help,but it looks like redfury has you covered. That great info.
ragenme If you can't fix it with a hammer then its probably a electrical problem!
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Re: Intermittent heat inside

Postby romeroom [OP] » January 12th 2013, 5:22pm

After coming back to this forum, I am always blown away by the amount of help and support you are all willing to share. Many, many thanks.

So, which heater core hose do I put a scalpel to and attach the pluming for a flush?
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Re: Intermittent heat inside

Postby romeroom [OP] » January 12th 2013, 5:26pm

tedanderson wrote:X2 on the coolant level. This had been an ongoing problem for a couple of years on another vehicle that I own. I pulled the cabin air filter and it got better for a while but once I was able and willing to bite the bullet and get that special red antifreeze, the heat became hotter than a summer day. :banana:


I assume there's no cabin air filter on my Astro, correct?

What is the magic behind red antifreeze?
'2002 Astro LS, AWD, 41k miles, "W" VIN
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Re: Intermittent heat inside

Postby romeroom [OP] » January 12th 2013, 5:37pm

Last thermostat I replaced was on my old 1995 Astro AWD. Before I get under the hood, any tips on replacing it on a 2002?
'2002 Astro LS, AWD, 41k miles, "W" VIN
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Re: Intermittent heat inside

Postby Ragenme » January 12th 2013, 6:11pm

There is nothing great about red anti freeze. Unless you like the early death of your motor. Flush it out and put in 50/50 like redfury said.
ragenme If you can't fix it with a hammer then its probably a electrical problem!
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Re: Intermittent heat inside

Postby romeroom [OP] » January 12th 2013, 7:16pm

Ragenme wrote:There is nothing great about red anti freeze. Unless you like the early death of your motor....


In other words, red anti freeze could contribute to the early death of a motor?
'2002 Astro LS, AWD, 41k miles, "W" VIN
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Re: Intermittent heat inside

Postby redfury » January 12th 2013, 11:40pm

Dexcool has been known to cause issues with head gaskets. The additives in it make it last the approx. 100k service life, but they can cause problems, especially if the cooling system has been worked on prior to the service life. It's chemistry. The point of it was to have less maintenance required on a system that is usually neglected unless it NEEDS service. Y'know, trying to eliminate the lowest common denominator.

The thermostat isn't any harder to replace than the previous generation. Two bolts. The newer style uses a rubber gasket ( not sure if your motor does ) that wraps around the thermostat and makes replacement as easy as you could hope for...almost fool proof.
A temporary fix usually becomes a permanent solution, therefore it does not exist.
doghouse removal by me!http://www.youtube.com/watch?v=uIJ0kuROlbU
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Re: Intermittent heat inside

Postby romeroom [OP] » January 25th 2013, 8:57pm

Replaced the thermostat and we're toasty hot again. Service engine light went away on its own. All is good so far.

Thanks for all the support.
'2002 Astro LS, AWD, 41k miles, "W" VIN
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