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Mercedes 6.9: Water Pump Overhaul

Started by jllgd, 03 October 2019, 04:28 PM

Randys01

I researched this topic deeply some years ago and culminated in me designing a new shaft and bearing assy. ..it works a treat. I am convinced that anyone offering an overhaul repair service resorted to the same thing I had to......the original bearing cannister is no longer available so rebuilders have had to come up with  something else.  It's not rocket science but I can see that hereonin, getting the vane impellor is going to be the show stopper.  As highlighted the 600/6.3 is just different enuff to hose down the obvious interchangeable unit hope. So some one with the smarts and means to recreate a 6.9 impellor is on a winner.
I will buy 2.!

john erbe

This took place several years back and if I recall my trusty mechanic, after describing the higher temps. told me that as a result of a different size bearing the impeller was now shifted to the wrong place.

TJ 450

It might be worth measuring up an M117 impeller for comparison as it looks to be a similar profile to the 6.9 one.
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

PosedgeClk

Thanks, John. Thanks, TJ.

TJ, do you have a part number or photo of the M117 impeller that you are referring to?

As for John's input, that does not surprise me at all that the performance of the pump changed when the impeller's location was changed. You can't change a single thing in one of these designs without likely affecting the performance. If I make an impeller out of billet 304, the vane contours are going to be very close to those of the original casting. I would go so far as to 3D printing a negative of the part to fit into an original part to check that my model is right.
1979 450SEL 6.9

Randys01

If you refer to the Tech Library, you will see a spec for the impellor clearance on the 6.9 water pump and that is the key ...........