W204 C220cdi 646811 Overheating

Vici

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Joined
Jun 17, 2021
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Your Mercedes
C220cdi 2008
Hi, I have a problem on my C220 CDI. The car will over heat and the blowers in the cab will blow cold, I removed the thermostat and checked flow and found out if I left the header tank cap off then the heaters in the cab would get warm. I've heard these have an auxiliary water pump and if so I believe that it is struggling to pump when the system is pressurised. If this is true does anyone know of the location of said pump? Or is there something else I could be missing. Thanks for any help.
 

MJJ

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Jan 15, 2020
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Location
Wiltshire
Your Mercedes
'09 S211 E220 Cdi manual - 185k miles and counting
Is the car losing coolant?

If so, a simpler cause might be that the header tank cap has failed. Had this on a Peugeot, and it would leak coolant out of the pressure cap - when the coolant gets low, no warm coolant gets to the heater matrix and the cabin heat stops. When the coolant gets very low, the car will start to overheat.

Martin.
 
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V

Vici

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Your Mercedes
C220cdi 2008
  • Thread Starter
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Is the car losing coolant?

If so, a simpler cause might be that the header tank cap has failed. Had this on a Peugeot, and it would leak coolant out of the pressure cap - when the coolant gets low, no warm coolant gets to the heater matrix and the cabin heat stops. When the coolant gets very low, the car will start to overheat.

Martin.
There are no external leaks and the header tank is retaining pressure, annoyingly the cab heaters actually work when the lid is off. It's starting to baffle me
 


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