There is a rebuild kit part number from the dealer and other sources which includes a new plunger, gasket etc. It's cheap. Simple to install and it will cure the heat always on issue. Good time to do a coolant flush anyway so, drain all of the coolant. Dave Hall I seem to remember a discussion about rebuilding the E28 M5 water valve (but couldn't find it with an archive search), the electrically controlled valve that controls coolant flow to the heat exchanger for heating the car interior (it's located on the firewall with the "battery terminal" on top). My AC works poorly, but I think it is fighting warm air allowed into the interior because the water valve is not shutting off. The electric control signals to the water valve appear to be fine for the various thermostat positions, and the valve itself "clicks," but residual warm (not full-hot) air blows into the car when the interior thermostat is set for full cold position, and AC gets cold but not really cold. Has anyone rebuilt their water valve? Any good way to drain the coolant (other than a shop vac) without making a mess in order to remove and test the valve? Thanks, Joe.