caution: vac pump rebuild kit for 617.952
 

Successfully completed the rebuild of the vac pump (single line, piston style) on my 617.952 two weeks ago. Worked beautifully until yesterday when the self-locking nut that holds the piston on its shaft decided it no longer wanted to stay where it should and blew a 3/4" hole through the center of the vac pump face plate:eek:. I found the center of the plate sitting on the core support but the nut was long gone. It scored the threads on the shaft a little as well as the center of the piston (by the hole) before its escape. It may have been my fault but I suspect it was a faulty nut- no way of knowing now. In any case, make sure you triple check this nut (and everything else) before/during re-assembly!
My indie friend had a spare pump (housing, and its insides, etc. $175), luckily, and I will be installing that tomorrow. Replacing the whole housing assembly with a known good one (instead of just a new nut and faceplate) to be safe in case I pull this pump and find more damage...
I really wish these things could happen during warmer weather...

It seems the worst repairs always have to happen in the cold....then again it could just be that the cold weather is harder on the components in general.

So far my 300SD has gone all winter with the only issue being a frozen/torn window seal on my drivers door. :D

Then again.....having done 6,000 repairs in the past 5 years....it'd better not have anything break!

what came w/ the kit?

was the nut original or replacement?

Standard vacuum pump repair kit by Mehle from Fastlane (Phil). You reuse the washer, replacement nut.

I believe I had a similar failure when i rebuilt my pump awhile ago. Created a hole in the piston. I replaced it with a junkyard swap unit that has been OK so far.

Thanks for the Heads-Up!!!

Insurance: degrease the threads and Nut with brake cleaner.
Assemble with your favorite Loctite.

Or use a center punch and stake the nut/threads in severa areas. This works but you may need a Die to chase the threads on the next rebuild.

In hindsight, I can't remember if I put any loctite on there...
Anyway- good advice. Now to get this new pump on before the Steelers beat the Ravens in the AFC championship game:D

Meyle or Mahle?

Meyle, sorry