Heater Core Flow, Clarification needed
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Member
Joined: Oct 2008
Posts: 179
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From: Chicago, Naperville area
2005 Mercedes S600, 2004 Mercedes E500 4-Matic, 2002 Mercedes C32 AMG, 2001 Trans-Am WS-6
Heater Core Flow, Clarification needed
In an effort to fix my heating problem, I want to try to flush my heater core. I wanted to get clarification if possible to make sure I understand fully. I've looked at a diagram (attached) showing the flow of coolant going in through the bottom of the heater core from the engine, then splitting into the two left/right core outlets at the firewall behind the airbox (presumably the left and right climate controls) which lead to the dual (heater control) valve.
Am I correct in assuming that if I wanted to reverse flush the core, I would need to apply air/water flow to both top "outlets" at the same time (the ones leading to the dual valve) and exit from the bottom? If that is the case, how do I get to the bottom hose intake? I can't see it looking down into the engine bay after removing the airbox.
The reason I think the core may be clogged is that the rear seat climate controls work just fine (which leads me to believe that coolant flow from the engine is good) and I have also replaced the entire front dual valve assembly (including pump) with a new one and it seems to be running properly. Also if I unplug the power from the dual valve, I would think it should open fully, and I get the same symptoms (no heat at highway speeds from front vents, only at idle...but rear vents work fine).
Thanks!
Am I correct in assuming that if I wanted to reverse flush the core, I would need to apply air/water flow to both top "outlets" at the same time (the ones leading to the dual valve) and exit from the bottom? If that is the case, how do I get to the bottom hose intake? I can't see it looking down into the engine bay after removing the airbox.
The reason I think the core may be clogged is that the rear seat climate controls work just fine (which leads me to believe that coolant flow from the engine is good) and I have also replaced the entire front dual valve assembly (including pump) with a new one and it seems to be running properly. Also if I unplug the power from the dual valve, I would think it should open fully, and I get the same symptoms (no heat at highway speeds from front vents, only at idle...but rear vents work fine).
Thanks!
Last edited by marktan; Oct 31, 2011 at 03:16 PM.
Super Member
Joined: Dec 2007
Posts: 980
Likes: 225
2005 S500 Designo
I went down this rabbit hole
I have some documents that might help.
It's not so simple. I wouldn't assume the heater core is clogged. I replaced the pump unit 2208350064 b/c I knew mine was weak/crunchy (had corroded on the inside).
All the lines felt hot.
My current guess is some flapper valve in the system, or maybe the solenoids aren't functioninig as they should, but I pulled them apart and they seemed to be moving fine. Also all the lines were hot. I think it's a mixture control valve in the system. See the attachments. Pls report back w/findings.
I have some documents that might help.
It's not so simple. I wouldn't assume the heater core is clogged. I replaced the pump unit 2208350064 b/c I knew mine was weak/crunchy (had corroded on the inside).
All the lines felt hot.
My current guess is some flapper valve in the system, or maybe the solenoids aren't functioninig as they should, but I pulled them apart and they seemed to be moving fine. Also all the lines were hot. I think it's a mixture control valve in the system. See the attachments. Pls report back w/findings.
