Hydraulic to Vaccum servo conversion

[robo]

Audi A8 D2 vac serv is a massive lump. OK for LHD but may be a problem in RHD application.

Any servo such as A4 B6, B5, B3 should be fine.

Just did the pump mod as fitting an AAN to a B3.

Would you know if a8 rhd sevo would fit lhd car?
I am trying to get all the parts to convert my lhd Ur to vac servo, not sure if local breakers would help me or is better get the stuff from europe.

[Ryss]

I will take a pic or two of the A8 and A4 boosters. A8 should fit with no problem in LHD.

Just very big for RHD where proximity to engine inlet, throttle body could be a problem.

Also, will clarify bolt / attachment layout. Off hand, A4 is bigger diameter but shorter in over all length than the A8, if my memory serves me correctly.

[Ryss]

Here are the pics of the A8 and A4 B6 boosters.

A4 fits. A8 does not fit thru attachment plate and therefore pedal set, as the nose piece dia is too big.

Also note length from firewall to end of master cyl, is shorter on the A4 unit.

[robo]

Thanks for the info.

[robo]

A4 B6 boosters.

A4 fits.

Also note length from firewall to end of master cyl, is shorter on the A4 unit.

Are you sure about a4 b6,I have one of these a4's and it has double servo, looks different then the one in your picture.

[Ryss]

Sorry.. My mistake. Not A4B6 . Its a A4B5.

[Error404]

For reference I just bought a vac servo off a 2.0L cabrio with P/N 8A2 612 105 A

[tajgreidotu]

IIRC I heard some where is that the difference between 105A and 107A is the size of it. I have 107A (an inch bigger) one and fits perfectly, but dont know how size affects.

[robo]

http://www.ebay.co.uk/itm/2008318148...84.m1439.l2649
I just bought this one from 2000 a4, I am trying to fit it to lhd ur quattro, will see when it arrives.
Thanks

[Error404]

IIRC I heard some where is that the difference between 105A and 107A is the size of it. I have 107A (an inch bigger) one and fits perfectly, but dont know how size affects.

Yes I think you are right on the LHD, but I don't think there is room for a bigger unit on the RHD as the servo is closer to the suspension turret, there is only one size vacuum servo in RHD.

Lets not complicate matters by comparing LHD and RHD parts though

[RS2]

Just out of interest, has anyone had issues with the one way check valve going bad and losing boost as a result?

I have an AAN in my Vanagon Syncro 16 which makes only 11-12psi (chipped ECU) and my brakes are now very hard to work!!

The van has been parked up for a while as we've just moved house but my daily driver Van (Tristar Syncro with 7A) developed a fuel injector body leak so I'm driving the 16 today.

MG

[Error404]

A couple of things you can check - pull the vacuum line off the servo and hold your thumb over it, start engine. You should feel a good vacuum on it. Switch off engine. It should hold vacuum for a while - if not the check valve leaks. If it does I am sure boost will not be doing the servo any favours!
Also check the seal between the master cylinder and the servo. A brake fluid leak can damage the seals and get inside and also damage the diaphragm.

I have two check valves inline on mine as insurance against boosting the servo. One is the OE check valve the second one is ff a TT - I figured that would be designed to take boost.

[A80Avant]

In my retrofit we used a one way valve from a Citroën which seems very robust. It's been a while I opened the hood of the car to check the valve but I will check and see if I can find a part number.

[popdemonic]

I had a black one way valve from VAG cars but not sure if it was taken from B5.working flawlessly just make sure you
plumbed her on the correct direction.I remember the check valve has a 2 small nipples available for another system that required the vacuum soruce as well.i just plugged them off.

[sailaz]

Here are the pics of the A8 and A4 B6 boosters.
A4 fits. A8 does not fit thru attachment plate and therefore pedal set, as the nose piece dia is too big. Also note length from firewall to end of master cyl, is shorter on the A4 unit.

In my RS2 I have fitted the double one from A8 D2 (4.2) without any problems ....