p/s kaput - pump or valve in box @315k miles
 

I've seen reseal kits for a p/s pump - but not a rebuild kit. How do the light alloy vickers pumps fail? Can they be tested? I hate to buy a pump and install it only to find my problem is in the box.

Anyone have test procedures for this?
I'll start with proper belt tension and fluid level.

I have never seen a failure on the aluminum or cast-iron pumps. I have seen them in obviously worn-out condition that still pump fluid and are quiet.

I think the reseal kit is all you need...Bert

The seal kit will only help if the unit is leaking. What do you mean by "kaput"

no more power steerting assist
 

I now have zero assist at low speed. The steering gets light once i get going, but i think that is more a function of lower effort when the car is in motion. The pump never sounds like it loads up when the wheel is turned.
Instant failure. No period of increasing effort. Fluid level is fine.

ZAFFO:

There is a pressure regulator in the system and the MBZ manual gives the specification for the pressure test procedure.

I thought your question was a general theory about the life expectancy of the pumps...Bert

Thought this link might help
 

Try this link for some help
http://mbpumps.com/index.html

I just got done rebuilding my pump. When I took off the pully and pulled off the rear acess door, the impeller came out. It has little metal teeth that glide in and out of the cylinder like fan blades. The faster you go, the further out they run, the slower, the further in they go toward the center of the shaft.

My guess is that some of these are stuck from debris or possibly wear and if they did, the fluid would not move at the correct rate with speed of engine. That could potentially create a problem. Pump was an easy rebuild. My 82 300sd pump had a front shaft seal and two o rings on inside of pump where the impeller goes. If these interrior seals have gone, the pump will not leak fluid outside, but it will not operate properly. I think the parts cost all of $12. Just make sure you get the front seal. It is separate.

punp looks OK - on to steering box
 

I pulled the pump out and took it apart and cleaned it out. The pump section itself (shaft and vanes in the impeler) looked fine. No evidence of binding or sticking. The valve and spring under the 30 mm nut looked a bit gummed up. It didn't come out too easily when the nut and spring were removed. I cleaned the housing and valve realy well and will reassemble with re-seal kit.

I'll look in the manual and read up on the steering box and any valve in there that could be stuck. At this point i think that I'll reinstall the pump, plug the return port and run several quarts of new oil though the pump and out the return line into a bucket with wheels off the ground and my assistant running turning from full left to full right, thereby flushing the box to see if that cleans out any junk in there that is stopping the show. If not, then I'll go deeper into the box.

Thanks for the tips fellas!
zaffo