Scirocco Register

James I checked the one way valve and it was busted. Air was going both ways. I changed it for a good one that works but now every time I press the brake pedal the engine revs up!? The engine idles a bit rough but when the pedal is pressed it revs up. If I hold my thumb over the pipe going into the servo the engine does not rev up with the brake pedal pressed. The idle is still a little rough though the carb might need a little tweak. Withe the new one way valve fitted the brake pedal seems like it has assistance but the car revs up. I am still going to change the servo with the second hand one I get tommorow.

james butler wrote:the master cylinder is annoyingly longer on the 16v where it goes into the servo so the shorter 8v cylinder doesn't work with it.

Ah, that's annoying!

I'm actually tempted to try out one of those bias pedal boxes and remove the whole current assembly

thats a bit odd, i dont recall the revs increasing? if any thing mine will stumble a little if you repeatedly press the brake pedal.
im going to have to go try it now!
the one way valve is there to try and maintain as much vaccuum as possible under the varying load conditions so it will improve braking slightly whilst idling and what not it isnt going to fix a servo that doesnt work so i think you may be right and changing your servo is going to be the only way to find out if its really bust.

Finally got around to changing the servo. The old one came out handy enough but it was a bit of bugger to get the new(second hand) one back in. The small clip on the clevis pin broke my heart to get in. But with some patience and loads of swearing I finally got it in place. The rest was handy enough but then I had to bleed the whole system about 3or 4 times to get all the air out and get a decent pedal. The brakes are grand now,much better than before so the old servo must have been on its last legs. No more revving up or down while pressing the brake pedal either,thank god ! I decided to do a post mortem on the old servo so I attacked it with an angle grinder and cut the front face off it and as suspected the rubber diaphragm perished/split at the lowest point when fitted on the car.if you get what I mean. And it had perished and split because the lower part of the servo casing had engine oil in it and it had softened the rubber diaphragm and it must have split when I stomped on the pedal when I had the crash.I reckon the oil must have been leaking past the dodgy one way valve. Anyway all sorted now. Thanks to everyone who offered advice.

Good to hear it's fixed.