Hydraulic to Vaccum servo conversion

[diesel des]

Ahhhhh this is becoming stupid now. So I recieved a replacement servo for the faulty one i got that seemed to be leaking when it wasn't preloaded. The replacement is leaking badly around one of the pressed together seams. So I pulled it and another one apart to see if I could make a good one. And no is the answer. Well maybe if I put it together with silicone or something.





So back to basics here. Are these things ment to hold vacume. Do they need preloaded on assembly or not. Do they need sealed to the bulkhead or anything else I am missing. Surely this shouldn't be so hard. Help!!

[diesel des]

Thanks for the feedback I thought I was going mad!! Yea one servo operated and gave assistance ok but leaked when the peddle wasn't pressed. But that's the one I pulled apart and probibly nackered last night ffs. I'm using a d2 audi a8 servo. So what servo fits a urs car and works without a vacume pump. I thought this was a well traveled conversion path but clearly not. Have others used these just connected to the inlet manifold and put up with the leaking air noise?? Surely mot time would result in a fail?

[diesel des]

So where on the intake are you guys taking as a source for the servo. On my aan intake I'm coming from below the throttle on the 10mm nipple via a t piece for the crank vent setup and then on the other part of the t a check valve to the servo. Just thinking that maybe these servos need loads of vacume to seal up or move a valve off its seat or something. And maybe then I need a single dedicated 15mm ish feed to the servo via a check valve.

If this was the case then the suck test we have done might fail but a real good vacume might work? Clutching at straws maybe.

[macspring]

Des, ask Eric in Cork, he did this conversion on his B4 S2 Avant. He may be able to assist.

[Error404]

Not with the dual diaphragm booster AFAIK

[diesel des]

Another update of my saga. I recieved the forth servo today in the post. This is how it arrived at my back door.



This is really taking the pi55 now. So the first servo came in the "kit" I bought from someone on this forum and it leaked at the seal near the input area.

The second came from a dismantler on ebay and in all fairness it seemed to be the best in that it would give assistance but would leak at its internal valve if it wasn't preloaded.

When I complained he sent another unit which was my third. This leaked badly at the crimped join in its body. I took it and number 2 apart last night to try and make a good one but now have a box of bits and a leaking servo at the crimped join.

And now the forth one today is broke at a big dent on the crimped join. It's getting to be like a comic sketch.

So I'm at a point now that I want to go to a car parts place or dealer and buy a new one that will fit and work! So any part numbers and places to buy one at something less than a kings ransom that is known to work in this type of conversion? Is that too much to ask?

Come back "bomb" system all is forgiven!!!

[diesel des]

Oh and thanks guys for the assistance so far. Your keeping me sain.

[Error404]

So if you want to go with a plug & play servo, just use the C4 vac servo - 4A0612107A
Ref the dual diaphragm booster, no-one has done it yet in RHD AFAIK - breaking new ground is always frustrating & expensive IME
i'll see what ELSA has to say once I've had time to install it

[diesel des]

Ok good man. I suppose I do have 2 c4 tdi parts cars I could plunder but then the master cylinder is different too. At least I have proven that the servo fits no problems it's just how it operates which should be no difference lhd to rhd. When measuring these servos is it the largest diameter that's used. The servos I'm trying are about 9 inch.

This looks interesting if it works.

http://pages.ebay.com/link/?nav=item...184287&alt=web

Anyone know if the pcd of the bolts are the same on all these twin chamber servos? Cheers des.

[diesel des]

http://m.ebay.co.uk/itm/171394184287?nav=SEARCH

[Error404]

Not sure, I think they will be. The Audi engineered don't tend to change stuff if they can help it. I bought a new OEM C6 servo on eBay a couple days ago to have a look at, was only £40. It hasn't arrived yet. They are ten-a-penny, half the reason I want to use one

[diesel des]

Any link to the one you ordered eg does he have more? If it's due to get to you soon I could wait until you get it and maybe make a few measurements for me? Cheers

[Error404]

It should arrive soon but I'm going abroad tomorrow night for a few days. I'll see if I can find the link now, iirc he had more.

[macspring]

Not with the dual diaphragm booster AFAIK

Apologies, I made an assumption, which was wrong.

Need to read the whole thread.

The idea of the factroy C4 servo on lesser C4 models would seem like a good idea / solution ?

[Error404]

Looks like he's put the price up now but free post
http://m.ebay.co.uk/itm/190623003871?nav=SEARCH