W211 E270 CDI 2004 blows cool air when idling

morphix

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Your Mercedes
E-class W211 270 CDI
Hey there fellow drivers, so recently I have ran to this issue.

To explain it as clear as possible, problem is that when car is standby (idling, not driving), heater blows cold air no matter what position it is in.

When driving the car, all heater functions work as expected, hot air blows, but as soon as you stop and wait for a bit idling, cold air starts blowing (even though the engine is already warmed up and at working temperature).

I have read about heater control valve issues on this model, however I'm not quite sure if it is the case here, since people with broken heater control valve usually have no hot air blowing at all, while I do (when driving).

Any suggestions are appreciated!
 

LostKiwi

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Your Mercedes
'93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
Sounds like the auxilliary heater pump has failed - quite common.
Not sure where it is on 211 but on 210 it's drivers side just below and behind the headlight.
 
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morphix

morphix

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E-class W211 270 CDI
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Cheers for the insights! :cool: I will look for a new aux heater pump and update this thread once I've made progress replacing it.
 
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morphix

morphix

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E-class W211 270 CDI
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Alright, finally managed to get some spare time and replace the auxiliary heater pump. On W211 270CDI it is located near the SBC block (not visible in the borrowed picture, it is a bit deeper). But the repair itself is not that difficult, took me about 30 minutes. It is just a bit hard to remove hose clamps from it since the space is tight.
tzzLbr9.png


Anyways, heating now when standing still and idling seems to be back, everything works as expected. Thanks!
 


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