My tech has had two failures while trying to reseal the self-levelling /
tandem power-steering pump on our 1993 500E.

Both times they are slightly leaking at the FRONT seal of the pump.

Any insights on resealing these pumps ?

Thanks,
:-) neil

Ttt

I sent you a pm. Mark

FWIW, I located a low-mileage tandem pump, and they re-sealed that one, no issues so far (over 3-years).

:-) neil

I suspect they were not cleaning up the shaft where the seal rides... a little polishing with ~1200 grit sandpaper, or Scotch-Brite pad, should work fine. Re-sealing these tandem pumps is NOT a fun job... if you don't have the patience of Job, I'd spring for a rebuilt with a warranty.

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You must speak from experience . . .

:-) neil

Welll... sort of.

My E500 had the pump re-sealed by the PO about 6 years ago, and it started leaking from the front shaft seal again recently, so I re-sealed it again. My 500E had the pump either replaced or resealed by the PO also 5-6 years ago, and it looks like it has the same problem. I re-sealed my E420 pump last year, and I think it may be leaking again, however I haven't confirmed the leak source yet... hopefully the oil is coming from somewhere else.


When I took the E500 pump apart to re-seal it a couple of months ago, I noticed the shaft wasn't perfectly clean & smooth where the front seal rides, so I used the Scotch-Brite treatment and it seems to be working ok so far (but, check back with me in 5 years). I will probably be doing the 500E tandem pump in a few months.

Now, the actual process of taking these apart and re-assembling them is a real nuisance. The plain power steering pumps are not too bad, but the tandem pumps are afwul. The worst part is getting those blasted locking rings off the shaft, and on the tandem pump there are two of them - one for the p/s circuit, and another for the SLS circuit (at least on the Vickers/LUK tandem pump). The SLS clip is held in by a thin lip of metal on the main center shaft, and when prying the clip out, the metal edge can easily break. There's very little left holding the clip in place on my pump... the previous tech damaged it, and I added to the damage when I pried it on & off 5 years later. Next time it will have to get returned as a core and replaced with a rebuilt pump.

Another tip for tandem pump re-sealing... if you are not getting PS and SLS fluid mixing (i.e., fluids mixing between the front & rear circuits), and the center seal appears ok... LEAVE IT ALONE. That center seal can be extremely difficult to extract without damaging the pump housing. Once again, if you screw it up too much, you'll be buying a rebuilt pump anyway...

I have a SLS pump without the pistons and springs; otherwise the pump is good.

Does anyone have a set of 4 pistons and 4 springs that I could buy so I could complete the repair of this expensive pump.

These small parts are not available via the dealer.

Thanks,

James.