I am getting a thump from my aux. water pump that can be felt and heard.No temp problems or coolant loss just this annoying thump.
Could there be an air pocket in the system,can it be bled?
Car is a 91 300E 24V M104.

A little thump is normal. The monovalve opens and closes many times per minute to handle temp inside the car. Due this abrupt "stop'n go" of coolant flow, you can feel and hear an intermittent thump and a little movement of the aux water pump. That's why this two devices are rubber mounted.

What's more, Aussie delivered W124s got two monovalves for the climate control system we have with separate temperature dials for driver and passenger side. This presumably gives even more "thumping" than the US deliveries with a single monovalve (pushbutton climate control with single temp dial).

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.

Thanks for the replies guys,it puts my mind at ease!