HOW TO: Re-sealing ZF tandem pump (SLS and power steering)
OK, I fibbed a little in the thread title. This is not a hold-your-hand re-seal procedure, just some photos of the process, and a few tips. I don't think there are any other threads with this info yet. (?)
EDIT: Yeah, there was, Gerry already went there and did that. Merged my piddly post with his mega mondo thread.
The pump on my project car was leaking like a sieve - possibly worse. Photos of that coming later. I had a good spare pump on the shelf (thanks, John!) and decided to clean and re-seal the spare pump, which allegedly had low miles (under 70k, IIRC) and should have been in better shape than the leaky pump with over 190k on it. Interestingly, the pump appeared to have been re-sealed once before, despite the low mileage. I don't know if it would have leaked or not, but given the difficulty of R&R'ing the pump, I didn't want to install it without a fresh front seal.
The factory procedure is at the link below. FSM job number 46-0730, section C. Start at PDF page 26 of 42. Note that the procedure is written for both ZF and Vickers/LUK pumps, which are NOT the same, and you'll need to interpret the instructions along the way to make sure you are following the proper directions. Photos attached below are for the ZF pump only! The Vickers/LUK pump is quite different. Oh yeah, the link:
http://www.w124-zone.com/downloads/MB CD/W124/w124CD2/Program/Chassis/46-0730.pdf
- Photo 1: Main 4 bolts removed, rear half of pump separated from front half
- Photo 2: Flat "barbell" shaped pressure plate removed
- Photo 3: Cam insert removed, rotor & vanes exposed
- Photo 4: Snap ring removed, rotor & vanes removed
- Photo 5: Drive shaft removed
- Photo 6: Main front seal exposed. This is the seal that leaks SLS fluid (NOT power steering fluid)
- Photo 7: Front cover removed
- Photo 8: Back side of front cover
- Photo 9: SLS section of pump exposed with front cover removed (Note: Internals NOT removed)
- Photo 10: Front cover temporarily re-mounted, front seal removed
- Photo 11: Front cover with seal removed
- Photo 12: New seal in position
- Photo 13: New seal pressed into place with super-special tool (27mm Sears socket)
- Photo 14: Top of rear pump section removed (power steering fluid inlet)
- Photo 15: Snap ring info
- Photo 16: Seal kit contents
Photos are also on my website
here for non-forum members who don't want to sign up just to see the pretty pictures.
I've done this a few times and 99.99% of the time, the only leak is SLS fluid from the front shaft seal. (If you are leaking PS fluid, it's probably coming from the hose above the pump, or the reservoir, or other hoses... not the pump itself.) Unfortunately you need to mostly dismantle the pump in order to replace the one offending radial seal. I chose not to take apart the SLS pump internals to replace the couple of O-rings inside, as this adds quite a bit of time and complexity, and IMO is not needed 99% of the time.
I also did not attempt to remove the center shaft seal which separates the SLS fluid section from the PS fluid section. This center seal is almost impossible to remove and it
almost never needs replacement. If your car is not mixing PS and SLS fluids, you don't need to replace the small shaft seal buried inside, just leave it alone. I replaced the O-rings for the front cover, between the halves of the pump, on the back of the 'barbell' separator plate, and the top PS fluid inlet, just because those are not difficult to replace.
Side note: The torque specs for all the bolts are very low. If you don't have a torque wrench that goes low enough, just make them snug. A previous MuppetMechanic™ managed to strip the threads on one of the eight bolts which hold on the front cover of this pump. Only a real gorilla, or idiot, would use that much force on small aluminum threads.
