Hydraulic to vacuum servo conversion

[tajgreidotu]

Hi guys,

I´m going this way with my 3b. For the steering I´m going to use an A class electric pump, and for the brakes.......after reading all the posts I dont have a clear idea.

finally, what the best combination for the brakes? V6 brake booster + v6 brake lines + 3B master cilinder?

Thank you so much, and sorry for my bad english!

[A80Avant]

http://12v.org/urs/Vacuum%20brake%20booster%20conversion.pdf

i followed this list and Marc Swannson (efiexpress) got all the parts from me. Master cylinder is the same as the one on the RS2 so no need to change.
I am using the OEM hydraulic PAS pump with the 2 pistons removed and the brake output tapped. That's the only way it will work. Pistons are located under the 2 black taps with the big cross on them.
Brake hydraulic servo is removed and lines are either going to be tapped or taken out of the equation alltogether.

I am having this done next week so ill post the results. My crossmember will have to be redone maybe and the fuel lines moved slightly.

[tajgreidotu]

Thank you sooo much!

[tajgreidotu]

I´m trying to decide which way to go:

- Electric pump (A class)
- Audi Coupe pump

But im a bit confused about what should I do to convert the hoses in each case..........Can I use the normal pump hoses with the S2 steeering rack??

Thanks in advance!

[A80Avant]

you can use the OEM steering pump and plug the hoses. What you need to do is to remove the 2 screws that have the cross on them, and remove the piston and spring, then retap them and tap the exit that used to go to the hydraulic servo. Tap the rest of the hoses from that system and it should work. Car is still at the garage, so i cannot say anything yet!

[tajgreidotu]

Thanks A80,

Im not sure if my pump is Ok or KO

Ill take a lot later!

[A80Avant]

Small update,
just for people to be aware of problems and issues and save some time, effort and £££...

I got the car back from the garage, who as i mentioned on a previous thread, they chopped and modified the original hose that goes from the power steering to the rack, because they 'couldn't modify it' to make it fit.

According to audi manuals, this hose has a loop at the end and that loop needs to have a specific mounting procedure. It has to have a parallel to the rack bolting and a 30deg angle after leaving the loop. The loop itself may be in any plane, so long as the rubber hose after the loop is at a 30deg angle with the rack.

The geniouses on the garage obviously did not listen when i told them that this hose cannot be replaced. It has to be reused, and went and made a braided hose for me. They insisted that everything will be fine.

After the modification of the steering pump to eliminate the dual vane action, they fitted everything back and although the brakes work nicely, there is excessive noise coming from the rack now, getting worse on lock turns. As at the time it was also leaking from the rack, they kept the car to fix that(now needing to remove the servo to reach the hose), and after explaining again why that hose should be used and perhaps a restrictor is in there, they said that they used a plastic hose that lies within the OEM pipe and that this had reduced the amound of noise produced.

That was absolutely NOT true as it still makes the noise and it gives you the impression that either the pump or the rack will get damaged soon. YOu also get vibration on the steering wheel while steering.

I am amazed how a simple metal loop on a hose that audi uses, makes all the difference. With the help of Pirvu Eugen, i will be sent a hose from an audi 80 i believe which it appears to be much flatter and definitely usable for this application to make the system work.

So for anyone trying to make this conversion, yes the brakes will get solved, but beware not to mess around with the OEM hose that connects the pump to the rack. DO NOT allow the garage to remake that hose. Modify it, bend the end of it a bit to fit, but do not use a braided hose.

the only thing i can think of is that the OEM RS2 hose has that loop in a more vertical plane than horizontal and that may have been the reason why the garage said that could not be used. However, that can still be bent and shaped, so long as the 2 ends of the loop have a 30deg angle between them...

anyway, it will get fixed and will work, just a bit more time and a bit more £££ im afraid....

[tscheel]

Small update,
just for people to be aware of problems and issues and save some time, effort and £££...

I got the car back from the garage, who as i mentioned on a previous thread, they chopped and modified the original hose that goes from the power steering to the rack, because they 'couldn't modify it' to make it fit.

According to audi manuals, this hose has a loop at the end and that loop needs to have a specific mounting procedure. It has to have a parallel to the rack bolting and a 30deg angle after leaving the loop. The loop itself may be in any plane, so long as the rubber hose after the loop is at a 30deg angle with the rack.

The geniouses on the garage obviously did not listen when i told them that this hose cannot be replaced. It has to be reused, and went and made a braided hose for me. They insisted that everything will be fine.

After the modification of the steering pump to eliminate the dual vane action, they fitted everything back and although the brakes work nicely, there is excessive noise coming from the rack now, getting worse on lock turns. As at the time it was also leaking from the rack, they kept the car to fix that(now needing to remove the servo to reach the hose), and after explaining again why that hose should be used and perhaps a restrictor is in there, they said that they used a plastic hose that lies within the OEM pipe and that this had reduced the amound of noise produced.

That was absolutely NOT true as it still makes the noise and it gives you the impression that either the pump or the rack will get damaged soon. YOu also get vibration on the steering wheel while steering.

I am amazed how a simple metal loop on a hose that audi uses, makes all the difference. With the help of Pirvu Eugen, i will be sent a hose from an audi 80 i believe which it appears to be much flatter and definitely usable for this application to make the system work.

So for anyone trying to make this conversion, yes the brakes will get solved, but beware not to mess around with the OEM hose that connects the pump to the rack. DO NOT allow the garage to remake that hose. Modify it, bend the end of it a bit to fit, but do not use a braided hose.

the only thing i can think of is that the OEM RS2 hose has that loop in a more vertical plane than horizontal and that may have been the reason why the garage said that could not be used. However, that can still be bent and shaped, so long as the 2 ends of the loop have a 30deg angle between them...

anyway, it will get fixed and will work, just a bit more time and a bit more £££ im afraid....

A small addition - I have a 80 converted to 7A - brake system also converted to hydraulics. The hose with the loop leaked, so i have had it repaired using the original loop - but I have the same noises as you. The difference in my case is the 4mm nylon hose that runs inside the original hose - it is missing in the replacement, so it allows for greater flow. I don't know if it damages the steering rack or the pump, but it sure don't sound healthy.

[A80Avant]

that is interesting, because if the 'plastic' hose they inserted in my braided hose is what this nylon one that you have, that contradicts the fact that mine still makes noise, even higher than before, although they used it!

Unless you need both the loop and the nylon fitting.

i am wondering if an inline restrictor would make a difference, although i dont think i would bother. I will just fit the OEM hose and take it from there. if it is still noisy, i will get a V6 steering pump fitted and rethink

[S2central.net]

YOu need to get a specific V6 hydraulic pump... some are single vane, some are dual vane. My 1992 V6Q has dual vane for PAS & Brake Servo - but there are some changes across the years with LHD vs RHD just to add confusion.

Its very weird about that special hose - no clue what is going on there.

[A80Avant]

wouls there be any difference between the RHD/LHD pumps? i would have thought that the pumps would be the same, but their hose would be longer on the RHD. Obviously if they list 2 part numbers for pumps, one for hydraulic brakes and one for mechanical, i would use the latter. I read on the pdf about the conversion mentioning that the V6 pump (single vane) mounts on the stock bracket, thats why i mentioned that pump. Otherwise any single vane audi pump would do with a spec of 75bar, it would just need a mounting bracket made to fit appropriately

[S2central.net]

Need to look at parts system. There was deffo something odd there I vaguely recall when looking before. Someone had asked me if pas pump from my V6 would work in s2/rs2

[tscheel]

Unless you need both the loop and the nylon fitting.

i am wondering if an inline restrictor would make a difference, although i dont think i would bother. I will just fit the OEM hose and take it from there. if it is still noisy, i will get a V6 steering pump fitted and rethink

I'm considering adding a restrictor to the hose, but don't hold your breath as the car is unregistered ATM - and it's replacement have a somewhat stronger magnetism on my spanners

The S2 got a replacement hose (and pump) shortly before I bought the car, so apperently the average loophose lifespan is around 17 years

[A80Avant]

the problem is that as i measured the ID of the OEM hose, it wasnt wider than 5mm anyway. So inserting a nylon fitting of 4mm, how much restriction does that cause? Its very odd.

[tscheel]

the problem is that as i measured the ID of the OEM hose, it wasnt wider than 5mm anyway. So inserting a nylon fitting of 4mm, how much restriction does that cause? Its very odd.

Sounds perfect - I roughly measured the restrictor to being 4mm - its running all the way througt the rubber part.

I'm just thinking that I could test a replacement hose with both loop and restrictor that way. The OEM hose is around 130euro for RHD cars I'm told. May be a bit less if bought from Germany.