hydraulic to vacuum conversion

[hunker7]

Time has come to get rid of silly hydraulic brake system as bomb has started pissing all over the road. I had a look at A80Avant (http://www.s2forum.com/forum/showthread.php?t=54144) post and his write up on hydraulic-to-vacuum conversion and seems pretty straight forward.

Does it matter which car I get a servo from? 100, 80 or I've heard A8/S8 servos are good? A8 setup is more widely available and can be bought very cheap on eBay with servo, master cylinder, clevis and fluid container so pretty much everything you need.

Car being a daily driver, how long does it take?

Tia

[steve briance]

I've done this on my CQ20v.

I 'think' it was an A80 servo but the p/n was 8A2 612 105 A.

Fitted a treat and came with all the vacuum hoses which was a bonus.

I don't know about removing the plunger from the pump - I've heard that this is not quite the best solution as it may sideways load the pump bearings as all of a sudden there is nothing acting on one end of the axle... At the cost of new (good secondhand) dual vane pumps thuogh it may be a case of so what it is only lasts another 2-3 years!

I used a pump off an ABK engine A80 and made up a bracket for it so the alu' 7A bracket still worked. The pump is the right operating pressure for the system and is designed as single vane from the outset.

I found the whole process quite satisfying and not too tricky though I would say beware undoing the servo nuts in the footwell, there are 3 and you can only see 2! I used many many extension bars and wobbles joints and it worked in the end. access was tight.

Brakes don't seemmuch different to before really if i'm honest but at least i know they are future proof and easily replaced with parts available out there

[s2dk]

Have had the same idea om mine
I have a a80 TDI that is being parted and was thinking of talking the vac booster from it and for my s2
My s2 bomb worls great But my pas pump is ****** noicy and was thinking to either use the a80 TDI or a spare s2 b5 that i have

[steve briance]

pics of the bracket I made. The flange i cut up was made from 6mm steel plate and was spare from a project i did years ago. Shows you why you should never throw things away!

the main issue is that the single vane pump is shorter than the dual vane item and the bracket needs to fill that gap. An afternoon in the workshop and an afternoon under the bonnet and now nearly 2 years in service and no bother.

If you have access to laser cutting, milling machines, lathes etc i'm sure you could make a nicer looking bracket but with only a MIG welder and a file I'm happy with mine.

[Albert]

So what car pump did you use ?

[steve briance]

050 145 155 A

2.0L ABK engine (and probably others)

you could probably knock up a batch of brackets for sale and i bet they would be quite popular...

[steve briance]

heaven's above, I've just found that the pump was also used on Ford sierras!

this opens up all sorts of bargain basement opportunities...

[Yuri]

Hi, I used this mannuals :

https://www.drive2.ru/l/288230376152418644/

http://audi-manuals.ru/remont-article/audi-a4/513-audi-s4-22-aan

https://www.drive2.ru/l/1860989/

[Bowie69]

Hunker, my conversion here, sadly with no pics (was in a hurry, a daily driver here as well):http://www.s2forum.com/forum/showthr...=69506&page=14

As in thread, took me 3 hours.

Servo part number I got was 8A2 612 105A, and included the firewall bracket, however I didn't actually need it, as the CQ20V has it already fitted.

I think the S8/A8 may be for LHD vehicles, which have some more room? That was my impression when I researched.

The part number above fitted the later cabrios, so not that uncommon really.

[RichLV]

I have vacuum assist on mine too. It was one of the first things I did when I bought the car, I'm almost 2 years on it now. Since it's a C4 like yours, everything is the same.

I opted for a standard vacuum servo from 2.8 C4. I did have to change it later, since it was torn and leaking vacuum, inducing a Mixture Adaptation fault. Everything else can stay the same. Even the pump. Just remove the pistons under X-plugs and plug the outlet for the bomb on the pump. I eventually changed the pump to a standard single contour, brand new TRW unit.

A8/S8 is a bit better, because it's a two membrane unit. But then you have to fabricate the connecting rod to the pedal, change MBC, change fluid reservoir.

[Bowie69]

Oh, and I got a rebuilt single stage pump from Alex! (error404)

[hunker7]

Thanks for the input guys. Don't want to do any fabrication work so D2 is a no go. If I understand correctly any servo fron that era will fit with no problems pretty much?

[RichLV]

Thanks for the input guys. Don't want to do any fabrication work so D2 is a no go. If I understand correctly any servo fron that era will fit with no problems pretty much?

Yes, even the B4 one. B4 vacuum pots just have the transfer fitting from 4 to 3 bolts, to fit them to the chassis. C4 doesn't need it.

Be advised, that it's a PITA thing to do on the first time.

[hunker7]

Sound. I'll try and get a C4 servo as I want to be as close to plug and play as possible.