RE: Heater valve
Is that the Silver Bullet/Cylinder looking things in the engine compartment under the plastic cover left side (wheel-well)? They look like a group of cylinders together. It's a rather expensive part! But if you need it, you need it. But could it be a problem with the temp control unit?
Best wishes with all that you endeavor to do
'08 Chevy Impala 2LT/FlexFuel
'02 Mercedes S430 w/S5 AMG Sport Pkg (Black/Charcoal)
'97 Mercedes S420 (SOLD)
'97 Cadillac Catera
'95 BMW 740iL