[urq] ATE Aluminum Brake Booster / Servo -- Update onRebuild ing kits

Eric Renneisen racingiron at comcast.net
Sat Jun 21 11:05:42 PDT 2008

Great work, Bob!  This is definitely a nagging problem that needed a
solution.  If you wanted to expand your market for these things
(assuming you want to put more kits together) you could advertise this
to the BMW crowd that has an almost identical booster, and the same
leakage problems.  The E23 BMW 7 Series (1986 and earlier here in the
US) has the same AL unit.  The rod that attaches to the brake pedal is
shorter, but everything else is the same.  The later bimmers with
hydraulic assist (E28 5-series, E24 6-series, E32 7-series) appear to
have a similar booster with just a differently positioned mounting
flange.  I haven't touched one of these yet, but they use the same bomb
and pressure regulator as the E23, so I'd bet the innards are the same.
These cars are also a good source of replacement parts if one has an AL
urq booster with damaged bits.

I've rebuilt an iron booster as well as AL.  Here is a picture of the
parts in the iron one:
Compare this with the image on Sean's instructions at Martin's site.  I
think there's just one seal difference, but I can't recall which.

Here are the differences for dis/reassembly:
- There's no rubber boot on the pedal side of the Fe booster like on the
Al one.
- There's an extra little collar and small spring inside.  I suspect
these are superfluous because the parts they mate to are identical in
the two boosters.  Nevertheless, I put them back in.
- The big, long spring is tapered in the Fe booster, while the Al one
has a symmetrical one.  This is because the metal end cap in the Fe
booster is a little wider where the spring mounts than the plastic end
cap in the Al unit.
- The Fe end cap is metal rather than plastic.  This is good, because
the plastic one breaks easily.  The oil seal is crimped in on the metal
one, but it's easy to "uncrimp" for removal and "re-crimp" when the new
seal is installed.
- The set screw has a metal cap that covers a normal hex head, rather
than the funky thing on the Al unit.
- The main difference is that the end cap on the Fe booster is held in
with a circlip rather than just the set screw.  You can remove the
circlip by pushing down on the end cap with the handle of a screwdriver,
short wooden handle, whatever, AFTER you've removed the set screw.
You'll be pushing against the pressure of the big spring, but it's not
too difficult to push the cap away from the circlip.  There is a notch
in the booster body that allows you to pry the circlip out with a

Other than that, it's the same procedure as Sean's Al write-up.

Eric R.
'86 urq
'92 urS
'93 urS

-----Original Message-----
From: urq-bounces at audifans.com [mailto:urq-bounces at audifans.com] On
Behalf Of Robert Pastore
Sent: Wednesday, June 18, 2008 1:59 PM
To: urq at audifans.com
Subject: Re: [urq] ATE Aluminum Brake Booster / Servo -- Update
onRebuild ing kits

This morning, I continued my insanity, and spent the morning driving
across the state to meet with a hydraulic seal manufacturer.
the owner of the business was a car nut too, and agreed to make the
2-piece Teflon piston seals (2 needed per servo) since the size was not
a stock item
in any reference book.   Minimum order was 50 pieces, or $250. So now,
invested almost exactly what a new servo would have cost!

I'll ship anyone who contacts me about a kit in the next week or so at
approx. my cost = $35 shipped.

The kit will include: 
see: http://www.quattro.ca/Urq/Brake_servo_guide.pdf

-The five o-rings & seal that are shown in the bottom left picture on
page 2 of the guide. -Two 2-piece pistons seals as shown on the piston
in the guide.  These are seals being custom made, and are Teflon outer
seals, each supported by an internal o-ring. -Part # 357 611 243 Gasket
between brake Servo and Brake tandem master cylinder (now with a dealer
cost of $8.91)

I'll have the piston seals by the end of the week, and I already have
rest of the parts on hand.   

I don't plan on keeping any kits on hand for the future (other than for
my own needs), and although I've now got a lifetime supply of o-rings,
the thick oil seal is hard to come by, and the pistons seals are being
custom made. So please, if you think you might need to rebuild your
servo at some point in the future, take one now.

If I happen to recoup my costs, i.e., have my fellow urq-ers request 15
kits, (so that my net cost is equal to yours) I'll donate a few kits to
URQ25, and the rest of the money to Dan.

Also, I owe a thanks to Sean, who *I think* is the person who prepared
guide that is hosted on Martin's site.   Also, another thanks to Ben
who is sending me an iron servo, so that I can identify the differences
in the internal components between the iron and aluminum servo.  I've
heard that one or two o-rings and maybe the seal are different.

If you have an iron servo, and want a kit, please email me.   I'll do
work to find out what changes I need to make, and if there's enough
demand to cover the cost of the changes, I'll go ahead and put a kit
together for the iron servo too.

Remember to register for urq25 North America this week -- the price
increases after Friday!

Best regards,


-----Original Message-----
From: Robert Pastore [mailto:pastorer at optonline.net] 
Sent: Monday, June 16, 2008 8:57 PM
To: urq at audifans.com
Subject: [urq] ATE Aluminum Brake Booster / Servo -- Rebuild kits

Thanks to Jim Pasqualoni & Ben Howell, I've been able to track down the
necessary seals and o-rings to rebuild the ATE aluminum hydraulic brake
servo. Martin Pajak has a great FAQ on the servo up on his site,
http://www.quattro.ca/Urq/Brake_servo_guide.pdf , but it seems that
nobody is putting a repair kit together anymore.

The servo part number is 857 612 107 A, and it has a current list price
of $725.81, and sells for $650.15 at Worldimpex.  There is no repair kit
listed in ETKA.

The parts needed to repair the servo are the 5 O-rings and 1seal listed
on Martin's site, plus I found and included the seal that sits between
the servo and the master cylinder which isn't show on Martin's page.

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