hydraulic pump rebuild

[New England: July-August & winter 08-Nov-1994 1443 <samaras@wrksys.enet.dec.com>]

Just as a word of experience, I have rebuilt an Audi hydraulic pump.  I would
not attempt this without the Bently maunual =OR= the factory service bulletin.
Either of these are ok, and the give you secret information that you would
never know. For example, it tells yuo how to make the tool to get those "X"
screws out (a special snapon socket). Also, it's very important to use a torque
wrench and use the proper values for each step of the reassembly process.

Anyhow, I did all of this and the pump leaked again within
a week.

Here's a summary of my experience with these pumps:

-If the pump only leaks from the X screws, get the less
 expensive rebuild kit and replace the O-rings under
 these screws.  It'll probably stop the leak forever.
 Don't take the pump apart.

-If the pump is leaking from the seam of the 2 pump halves
 (like mine) rebuilding probably won't help without
 machining the pump halves. The pump body gets distorted
 and no rebuild kit will fix that.

-If the pump was leaking at all, that can be caused by
 "excessive back pressure". Disconnect the banjo bolts
 that connect hydraulic lines at the pressure accumulator.
 There's a screen made onto the end of one of the bolts.
 This screen usually gets clogged.

With all the work it takes to remove and install the pump,
you're better off to get a good deal on a rebuilt one. Once
you have a pump that doesn't leak, clean all of those banjo screens
and flush the hydraulic fluid every 2 years or so. 

my 2 cents,
...bill
DEC MAYNARD, MA