Doesn't the 603 water pump housing have a notch to clock the thermostat?

Sixto
93 300SD 3.0

Yes, I think it can only go the one way.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Yes, it's notched to be clocked in only one way. The side with the spring goes into the engine. All that is needed to replace it is a 13 mm wrench. I found it more efficient to take the top rad hose off and pour antifreeze in there till it was full, put the hose back on. then fill your tank and rad
make sure your heater is on when you start the car. I had the same heater problem. 99.9% sure that it's the monovalve. Probably a torn diafram. (sp??) A monovalve is only 4 screws to take off. No big deal.

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All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic