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Old 01-15-2005, 12:36 AM
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goldstone goldstone is offline
W126 Lover
Join Date: Oct 2002
Location: Dutchess County, New York
Posts: 156
Can flushing cooling system kill monovalve?

Just swapped in a new tranny and torque converter, finally putting the original to sleep after 245,000 miles. Car is shifting like new (actually better, considering the modifications made to the great rebuild I purchased from Ron at German Star!)

Anyway, I can't fully enjoy the ride yet, since I now have no heat in the cabin! The thermostat and water pump were working fine, so it had to be the monovalve. Sure enough, I removed it and the screen/filter was totally caked with debris and the rubber membrane was torn.

Now, I know these monovalves are notorious for failing (especially after 15-years of use,) and that it's a really easy and relatively inexpensive fix, but I don't buy that the timing of this failure was just coincidence...

Can flushing the coolant (as was necessary before transplanting the transmission) foul and/or rupture these monovalves? And if so, would it be a wise precaution to remove the monovalve piston insert and plug the hole before flushing-away?

1991 560SEL-Euro (185,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)
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