I have an '89 420 SEL. Can anyone tell me the bolt size and length for the housing that contains the thermostat and attaches to the water pump (this would be on the left side of the water pump if you were facing the front of the vehicle)? There are three bolts and they are all the same.

Hi! I was browsing through the board and stumbled across your question. In case you haven't found your answer yet, the three bolts are M 6 x 20. They should be tightened to just 10Nm.

Cheers!

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Eric

1991 560SEL-Euro (214,000 miles)
1989 420SEL (Retired from daily use at 325,000 miles; Use as donor vehicle)