Vacuum brake conversion - Does this plan look good?

[Jonas_R]

So I'm doing a vaccum brake conversion and just wan't to check if I got all parts etc:

My plan is to do this:

- remove the pistons in the power steering pump and remove the pressure hose that goes from the power steering pump to the bomb

- remove the bomb. Is there any hose from the bomp to the brake reservoir that needs plugging?

- Vacuum from the carboncanister hose to the brake servo. I bought a t-piece and vacuum hose with ID 12mm.

- remove the master cylinder and brake reservoir and replace it with a vacuum brake booster from audi 100. Part nr. 8A0612105E/4A0612107A 254mm


- plug the hose return from the servo to the power rack return hose with brake nipple. I talked to error404 about this, but I can't remember why it needs to be plugged?

I also bought the parts mentioned in this thread:
gasket for booster (431 612 193)
clevis (893 721 213)
clevis nut (n011 162 9)
clevis pin (443 721 371 A)
check valve (191 611 933 E)

I have 1 liter of brake fluid perhaps I should get some more? I presume I need to bleed all brakes and the clutch?

[popdemonic]

Jonas,
only thing you need to do is on the top of the brake servo,There's the oil return pipe that coming to join with the oil return pipe from steering rack.
you need to plug that off with bolt and all is done.

[Jonas_R]

Ok. Why is it connected to the brake servo?

[Error404]

Excess / bypass hydraulic fluid from the servo needs to go somewhere, it drains down to the return line from the steering rack. When you bin the hydro servo, you need to plug the joint in the rack return line, it's M10 x 1 so a bleed nipple works perfect, plus you have a ready made bleed point for the PAS circuit

[Jonas_R]

Please help my ignorance here.

What is hydro servo? Do the brake conversion mean that I loose power steering?

[varia]

use a b4 or c4 V6 ps pump with hose from a b4 v6 to the rack to the reservoir and call it a day
i used a booster from b3 cos itd an 1" small then one from the b4

[hunker7]

May I ask, what is the advantage over OEM setup?

[Jonas_R]

use a b4 or c4 V6 ps pump with hose from a b4 v6 to the rack to the reservoir and call it a day
i used a booster from b3 cos itd an 1" small then one from the b4

Ehm but is it necessary?

I'm still not sure if I will loose power steering or not by just removing the high pressure part of the pump. I thoght the lower pressure part was used for the power steering

[popdemonic]

the stock ps pump has 2 circuits as i stated above.
removing small pistons = disable a circuit for brake
assists either you might be using ps pump from the
car which is using the vacuum brake booster..
For Example.,we can use ps pump from 100/A6
ps pump.it's just bolt right up and all is set.

[popdemonic]

May I ask, what is the advantage over OEM setup?

you eliminated the chances of the system break down and cost a fortune when it comes
to service time.someone dislikes the "sponge" pedal feeling from the stock "Hydro system".I ever done the conversion with single diaphragm booster and been running
for years before swapped it back to stock hydro system since personally the brake pdeal
is way too hard when apply the brake.I plan to use the 1,5 or dial diaphragm boosters next time some of my friends has done it on UrS6 and you don't need to
mods anything .it's just bolt right up.

[Jonas_R]

the stock ps pump has 2 circuits as i stated above.
removing small pistons = disable a circuit for brake
assists either you might be using ps pump from the
car which is using the vacuum brake booster..
For Example.,we can use ps pump from 100/A6
ps pump.it's just bolt right up and all is set.

Ok so I do not loose the power steering, that was what I thought, but the statement from error404 confused me.

[Error404]

For Example.,we can use ps pump from 100/A6
ps pump.it's just bolt right up and all is set.

In the C4 chassis it's fine, C4 PAS pump pressure is 120bar, S2 is 100bar so it's not a straight fit in an S2. But you can bake a hybrid pump using S2 pump rear section & C4 pump front section.

[Giacomo]

How does the power steering feels on UrS6 steering wheel after this mod?
Does it feel as light as it feels on A6, or still "hard" and "handling-less" like on S6 with the bomb?

[popdemonic]

it's unrelated.power steering is separate function.

[hiloran]

Audi A8 servo is a nice fit. Same bolt pattern no adapter needed.