Hello all,

Since a while now I have air in the heating system. If I turn on the heater, which seems to work fine, I can always hear the airbubbles in the system. I have tried to get all the air out of the cooling system, even by slightly lifting the front of the car, but I do not seem to be able to get rid of it. While being at my Benz shop on other business I aksed how they bleed the system for air and explained why I asked. The technician there told me that this is usually caused by a faulty auxiliary water pump.
I have been reading up on this part in these forums and it sounds like a plausible story. The only thing I could not get out of the threads that I read so far is the location of this pump.
I drive a 1993 300e 2.8 24V (M104 engine). I do have something that looks like a swith mounted on the firewall just in front of the battery (when standing in front of the car). It has two cylinders (2-3 inches high and alloy colored) on a plate that seem to connect to the heating hoses. I am not certain which part this is but it does not really look like a pump. Where would I find the pump in this car? Would anybody have, or know where to find, a picture of the part and it's location?
Thanks a lot,....not for the first time,
Marc