Classic Audi Ľ Technical Ľ Mech/Tech Ľ Suspension & Brakes » ur quattro (WR '85) brake booster

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Old 29-06-20, 08:50 AM   #1
StoutyBoy
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Default ur quattro (WR '85) brake booster

Dear all,

I wonder if someone could please offer me some advice on the brake booster unit on my RHD '85 WR ur quattro?

The unit that sits behind the master cyl on the right side of the engine bay. It has developed an ATF leak from the knurled 'fitting' on the underside. I've attached a poor photo as the unit is still on the car and this was taken somewhat blindly from underneath.

Is this actually some sort of bleed nipple or am I likely to have a seal inside the unit which is causing the problem? I do plan to remove it shortly but thought I'd ask some experts first. I think brake boosters are difficult to come by so I guess it may need a specialist repair

Thanks

Paul
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File Type: jpg urq rs2.jpg (177.7 KB, 22 views)
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Old 29-06-20, 07:21 PM   #2
Steve
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They are available and periodically do need replacing. After running the car and then turning the engine off, how many depressions do you get before it goes hard?
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Old 30-06-20, 09:22 AM   #3
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Thanks Steve.

Depressions wise you get quite a few but ATF is dripping out of the underside of the booster all the while which is far from ideal. It'll empty the reservoir pretty swiftly. Do you know a supplier for these units if it can't be repaired?

I'll test pedal feel with the engine on and then off (need to get the car out). Recently replaced the bomb but the leak was already there prior to that.

Thanks again

Last edited by StoutyBoy; 30-06-20 at 09:24 AM.
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Old 30-06-20, 09:29 AM   #4
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IIRC, you can use a Citroen bomb instead. No idea if they are still available though!
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Old 30-06-20, 09:45 AM   #5
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Thanks. The bomb was easy to get hold of and only 90quid in the end. The booster is the bigger issue unfortunately
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Old 30-06-20, 10:27 AM   #6
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There is a fella offering rebuilds, I believe. Maybe S2 forum. A lot of commonality with some BMW stuff, it Iíve yet to look further as Iíve been distracted for a couple of years
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Old 30-06-20, 10:27 AM   #7
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Unless you are going for originality have you not considered dumping the hydraulic servo and changing to a vacuum setup?
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Old 30-06-20, 11:18 AM   #8
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Ok thanks. I’ll have a hunt.
In terms of a vacuum setup, yes would consider if this can’t be rebuilt or replaced. Would ultimately prefer it to be original but not at the expense of not being able to drive the thing.

Cheers
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Old 30-06-20, 12:38 PM   #9
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Which part do you actually need? The master or the pump? I may have a spare.
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Old 30-06-20, 03:53 PM   #10
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Thanks Dave. I'm not sure of the name of the component as I've seen it referred to as different things. It's the unit bolted to the back of the brake master cyl.

I've not disassembled it but it's the component shown at the foot of the attached. I understood it to be known as the brake booster (it contains and leaks ATF).
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