Hydraulic to Vaccum servo conversion

[AndyP]

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.

Do you have a part number for the TT valve?

[Error404]

058905291k

[AndyP]

For reference Forge are now making a billet one way valve specifically for high boosting cars with vacuum brakes:-

http://www.ebay.co.uk/itm/331470792631

[A80Avant]

Will these stick eventually like the rest of the forge valves?

[mihai_antony]

Hello

I have an 2,3 7A 20v audi, FWD, and I want to make the conversion to vacuum brake
It is better to use the parts from the 2,3 NG engine or the A4 B5 1.8T? The 7A produce enough vacuum for this conversion?

Thank you very much!

[RS2]

I use a 7A in my VW T3 Transporter Tristar Syncro.

It uses the vacuum servo, no problem. It has more than enough vacuum for the braking system.

MG

[krzysztofkabaj]

I'll add something from me. I converted hydro assist to C6 master cylinder, 8" booster and electric vacuum pump, exactly as in C6.





Sorry for Polish marking on pics, they were made for use on PL forums .

For control of electric pump was built control unit using old map sensor taken out of Motronic ECU .

[Error404]

That is on a C4?

[krzysztofkabaj]

Yep, S6 C4. Why asking ?.

[Error404]

Because the hole in the bulkhead is bigger on the C4 than B3/B4 chassis. The later dual diaphragm servo from the C6/D3 does not fit the smaller B3/B4 chassis without some modifications. You need to cut the bulkhead & modify the pedal box.

[krzysztofkabaj]

I see . There's no such issue in C4 chassis. Only problem with dual diaphragm servo U need to solve is brake pedal rod. In C6/D3 we get ball joint, U need to cut it some longer piece of rod, make new M8 thread and use C4's original "fork" joint.
I did not said the mod was easy but certainly was worth it.

[Error404]

Yes the thread is larger on the servo pushrod, M10 vs M8 so an adapter is needed

[krzysztofkabaj]

Thats correct. Wish I made some pics during conversion .

[Horsty]

Hi Guys,

sometime last year i fitted the a8 d2 brake booster and master brake cylinder in my 7A quattro coupe and i thought it might be interesting for one or the other...

7x8 inch brake booster combined with the 25,4mm master brake cylinder.
the other option would be the 26,9mm i guess. but that would be overkill.


adapter plate needs to be fabricated. otherwise the brake booster will be leaky.




a6 v6 hydraulic steering pump. quite the same pump used for a long time at audi.
a4 b5/b6 or B4 v6 is also the same. bolt on directly to the 7A bracket.


brake booster without grommet. you see these tubes coming out of the brake booster for the bolts.
the "tubes" are not the same level as the brake booster surface. thats the reason for the adapter plate i made.


adapter plate alignment.


difference between the hydraulic spacer (short one) and the vacuum spacer (long one).


adapter rod and the grommet mounted.


adapter plate, vacuum spacer, adapter rod and that kind of fork mounted.


this adapter needs to be fabricated to increase the rod length:


ready for installation:

[RS2]

I ended up buying an RS6 one way valve. It's much better but I'll be fitting a bigger servo soon.

MG