Hydraulic pump cap tool

Ameer Antar antar at comcast.net
Sun Nov 19 22:45:51 EST 2006

I won't pretend to know all the details of that system, but what I do know is that after replacing the "rebuilt" bomb with a new one, I got my power steering and brakes back, and no more check system warnings. Looking at the diagram on SJM's site, it does look like the check valve prevents any back pressure on the pump, but I don't know if the servo actually puts pressure on that part of the system.
The pump was rebuilt, but not by ZF. The tag was even removed from the pump. Other than the leaks, it's a lot better than my old one which probably had a bad front bearing since the pulley was wobbling all over the place and squealing up a storm. The seller claims the seals were replaced, so I wonder what I'll find under those caps. Either dried up seals or ones ripped up by strong backpressure... Or who knows what else... For now I'm stuck having to top up the liquid gold every week. Last week, I had the car in the shop and they filled it for me cuz they got the check system warning: $20 for a top-up! I didn't argue... at least they didn't put in transmission fluid...
-------------------- Original Message --------------------
From:Kneale Brownson [kneale at coslink.net]
To:Ameer Antar [antar at comcast.net], Quattro List [quattro at audifans.com]
Cc:cobram at juno.com, Frederick Smith [smitty at pcrealm.net]
Date:11/19/06 8:33:46 PM
Subject:Re: Hydraulic pump cap tool
I wouldn't blame the bomb for pump problems.  I think the check valve is only there to help the accumulator hold its pressure when the engine isn't turning the pump.

Was the ebay pump supposedly "rebuilt" or just a "good" takeoff?  I wouldn't trust ebay pumps unless they come with validation that ZF rebuilt them.

If you buy the seals kit referenced earlier, do the whole pump, not just the seals under the caps.  I'll bet that when you take the caps off you'll find the seals inside much harder than the ones from a new kit.  Best writeup I've seen on pump resealing is in the Bentley for 89-91 100/200.
At 07:21 PM 11/19/2006 -0500, Ameer Antar wrote:

Thanks for the tip to everyone who replied. I guess I'll have to change the seals too, even though the pump's only a few months old (bought it from ebay). I had a brake accumulator (bomb) with a bad check valve (one of those rebuilt ones). I'm not sure, but my guess is the leaky valve forced fluid back into the pump, instead of the brake servo, and may have busted the seals. Should I be worried about anything else?

I'll never buy one of those rebuilt bombs again. There's nothing in there that can be rebuilt if you can't replace the diaphragm. Too bad I didn't realize that before the bomb blew up my new pump! Live and learn I guess...


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