Radiator cap affecting heat?

Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 26th 2009, 5:36am

I am still fighting a low heat situation. The cooling system holds pressure just fine. The temp gauge is at 195. I can burp the air from the heater core all day and it doesn't help. I have even replaced the heater core. When that didn't help I put the old one back in, thinking the new one may be faulty. I have changed the heater control valve. The old one worked fine, and the new one does too. I have replaced old vacuum lines. I have great vacuum. Still almost no heat. Unbelievable. What is left? It hit me today, Christmas day. There is ONLY ONE thing left. Radiator cap. I noticed I can take off the radiator cap and there is no pressure AND THE COOLANT LEVEL IS ALWAYS DOWN an inch or two. I have never replaced the radiator cap. I wonder if when the thermostat closes and radiator cools, the worn out radiator cap is allowing the radiator to draw in air instead of coolant from the overflow tank. I can't wait to replace it and report back if I FINALLY get heat again!! That would be a wonderful Christmas present.
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Re: Radiator cap affecting heat?

Postby rev_les » December 26th 2009, 4:23pm

Have you checked to see if the heater control is making the blend door move to allow air to pass through the heater core? Just a thought, you've done a lot of work to still have nothing going to keep you from freezing yer rear off. :think:
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Re: Radiator cap affecting heat?

Postby tedanderson » December 27th 2009, 3:00am

What is your coolant to water ratio? For the winter I like to mix mine at 70/30 but no less than 60/40.

A mistake that I see people make (and I've done this too) is to fill the radiator with plain water to cover a low fluid situation (e.g. if there was a minor leak or some other situation that lowered the level) only to come back later and forgetfully top it off again with the 50/50 pre-mix. And because I had plenty of water in the system, my ratio was reduced to less than 50% coolant.
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 27th 2009, 5:43am

Unless I am mistaken, my 2002 Astro does not have a blend door for heat. It looks like all air comes in over the heater core and the heat is controlled only by the heater control valve. Am I mistaken? And my mix is 50/50 dexcool.
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Re: Radiator cap affecting heat?

Postby rev_les » December 27th 2009, 7:08pm

Vinnie6 wrote:Unless I am mistaken, my 2002 Astro does not have a blend door for heat. It looks like all air comes in over the heater core and the heat is controlled only by the heater control valve. Am I mistaken? And my mix is 50/50 dexcool.


That got me to looking in the FSM, and apparently there ISN'T a blend door...the air comes in over the evaporator and is re-heated by the heater core before entering the passenger compartment in A/C mode, and the temp control switch controls the heater control valve. The system regulates the coolant through the heater core to get the desired temperature. I don't know how the older vans work, I'm reading a '99 FSM, and we should have the same system with yours being a 2002.
What a pita....now come summer I'm going to have to replace the control valve or bypass the heater core...Some of these engineers need a swift kick the the kiwis.
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 27th 2009, 9:28pm

rev_les wrote:That got me to looking in the FSM, and apparently there ISN'T a blend door...the air comes in over the evaporator and is re-heated by the heater core before entering the passenger compartment in A/C mode, and the temp control switch controls the heater control valve. The system regulates the coolant through the heater core to get the desired temperature. I don't know how the older vans work, I'm reading a '99 FSM, and we should have the same system with yours being a 2002.


Rev,

What you describe is exactly how I see things to be on my 2002. I was wondering how you were going to keep cool in the summer with your heater control valve bypassed. Another thing about the vacuum operated heater control valve - Open is cool, closed is warm. Vacuum opens it. Therefore loss of vacuum will give you heat by default. If you have your temp set to cool and it is blowing cool, everything is working as it should.
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Re: Radiator cap affecting heat?

Postby tedanderson » December 28th 2009, 12:21am

Still almost no heat. Unbelievable. What is left? It hit me today, Christmas day. There is ONLY ONE thing left. Radiator cap.


Well there is one other thing that I didn't see mentioned- the water pump.

Yes, this is a long shot especially when it is evident that you have pressure in the system. But I wonder if this pressure is the result of the heated coolant but for whatever reason it's not flowing properly. When you open the radiator cap, can you see the coolant circulating as it's being discharged from the top hose or is it just standing? Also, I would normally assume that the smaller heater lines on the water pump would function if the larger radiator hoses do the same but I've seen stranger things go wrong with no good explanation.
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 28th 2009, 5:32am

tedanderson wrote:Well there is one other thing that I didn't see mentioned- the water pump.


Ted,

I thought about that too. When I pull the radiator cap, I cannot see the coolant circulating. It is just standing still. AND I can pull my top heater return hose (with radiator cap off) and there is just a small stream of coolant coming out. I thought it was due to airlock inside, but I sure thought that was a wimpy stream. I am taking it to a local repair guy. I'll mention it to him. I really hoped it was the radiator cap, but that doesn't seem to have made a difference.
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 28th 2009, 4:29pm

Ted, I have excellent rear heat. Would that rule out the water pump?
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Re: Radiator cap affecting heat?

Postby rev_les » December 28th 2009, 5:46pm

Could you have got the hoses mixed up replacing the heater control valve?? Is the valve allowing the proper amount of coolant through to the front heater core? Is it possible a hose is partially blocked? Just some things to check,the system's not that elaborate,it's some kind of simple gremlin. Good luck with it!! ( you could try temporarily bypassing that valve and see what happens.
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 29th 2009, 12:27am

***Guarded optimism***

My Father-In-Law's trusted mechanic has fixed my van. He flushed the heater core - ran water through it both directions, back and forth, for half an hour until the water ran clear and with full force. He said as soon as dexcool meets air it solidifies into black flakes and they get trapped in the heater core. It has been a problem with GM since the mid 90's. Flush it out and you're good to go. Every time I pulled the hoses off my heater core I was breaking into the system trying to fix it, but I was actually making it worse by introducing more air. Air is the enemy to dexcool. I asked him what to do if I ever have this problem again. He said get two lenghts of garden hose, one 5/8, one 3/4 diamater, and flush the heater core with water from both directions. But first, seal off the heater hoses with clamps so air can't get in.

Assume, unless you hear from me again on this topic, that my problem has been put to rest. Good riddance!
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Re: Radiator cap affecting heat?

Postby astroturf » December 29th 2009, 12:44am

Vinnie6 wrote:***Guarded optimism***

Assume, unless you hear from me again on this topic, that my problem has been put to rest. Good riddance!


Vinnie, I would add that until you get rid of the dexcool, You have only put off another problem. Perhaps next season. Just my thoughts, Jim
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Re: Radiator cap affecting heat?

Postby Vinnie6 [OP] » December 29th 2009, 12:59am

Anyone have an opinion on propylene glycol coolant, like Amsoil's? It is non-toxic, for one thing. How involved is the switchover? Just curious.
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Re: Radiator cap affecting heat?

Postby rev_les » December 29th 2009, 6:31am

If you're going to switch, make sure you flush the system thoroughly. Otherwise, it's straightforward.
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Re: Radiator cap affecting heat?

Postby tedanderson » December 29th 2009, 5:40pm

Not to jack the thread but what exactly is Dexcool and should I be using this instead of the standard "Brand X" variety?
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Re: Radiator cap affecting heat?

Postby Leeann_93 » December 29th 2009, 11:42pm

tedanderson wrote:Not to jack the thread but what exactly is Dexcool and should I be using this instead of the standard "Brand X" variety?


No! Your van did not come with and does not require Dexcool. Normal yellow stuff is what is needed in your van.
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Re: Radiator cap affecting heat?

Postby astroturf » December 30th 2009, 12:27am

What is normal yellow stuff?
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Re: Radiator cap affecting heat?

Postby Leeann_93 » December 30th 2009, 1:16am

Standard Prestone Antifreeze/Coolant.

Your van, on the other hand, came with the red stuff, aka Dexcool.
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Re: Radiator cap affecting heat?

Postby astroturf » December 30th 2009, 1:33am

Leeann_93 wrote:Standard Prestone Antifreeze/Coolant.

Your van, on the other hand, came with the red stuff, aka Dexcool.


Wasn't their a formulation change in dexcool about 2002 that made it better?
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Re: Radiator cap affecting heat?

Postby rev_les » December 30th 2009, 2:39am

astroturf wrote:
Leeann_93 wrote:Standard Prestone Antifreeze/Coolant.

Your van, on the other hand, came with the red stuff, aka Dexcool.


Wasn't their a formulation change in dexcool about 2002 that made it better?

I still don't trust it.
On the blend door subject, there has to be some way to blend the air because even with the heater control valve eliminated,my temp control still works just like it did before I eliminated the valve.I tested it today, and even turned on the a/c even though it was 32 outside, lol....
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