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Discussion Starter #1
the pipes going in and out of the heater core are hot, yet only luke warm air from the sides of the heater box and cold out the floor vents. the only vac element not working is the fresh air / recirulated air flap. What's not working?
everything else checks out.:confused:
 

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Is the auxiliary water pump (located near washer fluid reservoir) working? Is the heater valve (passenger side, underneath windshield cowl) working?

My dad and I had a problem with our 300 SEL for years, no heat. One day I accidentally took the heater cap off when the car was too hot (bad idea, was absent-minded). After that, the heat started working. The car may have an air pocket trapped in the heater core, so you may try burping the coolant system again.
 

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Yes,they are all working. Like I said, the tubes that carry the coolant into the heater core are hot to the touch, but it seems the flaps that allow the hot air to flow into the cabin are not working. I'm hoping this symptom is indicative of the #40 element not functioning, which it is not, in my case. I'm waiting for the replacement to arrive, I guess I'll just have to wait and see.
 

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Yes,they are all working. Like I said, the tubes that carry the coolant into the heater core are hot to the touch, but it seems the flaps that allow the hot air to flow into the cabin are not working. I'm hoping this symptom is indicative of the #40 element not functioning, which it is not, in my case. I'm waiting for the replacement to arrive, I guess I'll just have to wait and see.
I see. Does it blow hot air in the defrost position? It is my understanding that vacuum elements are designed to fail to the defrost position, full heat out of the defrost vents.
 

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I see. Does it blow hot air in the defrost position? It is my understanding that vacuum elements are designed to fail to the defrost position, full heat out of the defrost vents.
No. It's cold out the top, cold out the bottom and barely warm out the sides of the heater box, no matter what push button you push. Incidently, the luke warm out the side vents does go cold if the temp wheel is tunrned to colder. The potentiometer is functioning in what appears to be a normal fasion. :confused:
 

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Discussion Starter #8
Turns out the heater core is junk! I disconnected the hoses and could barely blow through. After removing it, when I filled one end with water, it would only trickle out the other. New one on the way!
 

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it sounds like someone used stop leak fir some reason and that stuff blocks ur heater core up it may just need a good flush to get the crap out.
 

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I'm not going to risk it. Getting to it was a royal pain in the ass, and I don't want to have to do it again!
 

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Discussion Starter #11
We Have Heat! Parts.com sent me a genuine MB core that I installed yesterday. Everything tests perfectly and it puts out bocoo heat. Now all I have to do is put the dash back in, no easy task. Thanks for everyones input.
 
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