W204 C220cdi 646811 Overheating

[Vici]

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]

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.

 

[Vici]

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