guards red

Well it would appear that I have gotten myself into yetanother mess. I've never found it easy working the pedals, the throttle seemed too far away if I had the seat adjusted so the brake and clutch was right. So today I thought I'd adjust it so I removed the floor board, removed the link and adjusted it so it was longer. So far so good. To make sure everything was okay at the engine end I took off the airblower fan and associated pipes and pushed my arm under the plenum to check the butterfly was fully open. It wasn't, but a few adjustments later all was well. I reinstalled everthing and took it for a run.

On my return I checked my vacuum guage, a guage I have permanantly connected to the varioram system and found it sitting at zero. Normally I can come back to it after a week of not driving it and still find 22 to 24 inches of mercury in vacuum. I do not have access to anything that can generate a vacuum (other than the engine) so I disconnected each circuit and subjected it to pressure to see if any pipe leaked. None did. The only ones i couldn't test were the pipes coming from the plenum with the one way valves. Mine is a C2, so it has two one way valves, one for the brake booster, the other to run the varioram with offtakes for the fuel vapour system.

My question is this - is my thinking right, if the varioram system pipes are okay, vacuum can only be escaping via these valves? Are they both one way valves? What is the purpose of the venturies behind the valves? Has anyone ever replaced these?



Thanks guys

Robin 993DX

It could be a leaking vacuum reservoir, you will find the bubble looking thing tucked under the left hand side rear wheel well area. Sometime if the cars are not jacked carefully you could damage the vacuum reservoir bottle there.

Of course it could also be a number of vacuum hose you accidentally disconnected during your repair.

guards red

Hi Robin, thank for your reply, much appreciated. I have checked everything, using my lungs to provide a vacuum where I could, and it turns out its the check valve that the vacuum distribution elbow is connected to. The elbow being the rubber piece that often collapses. It bleeds vacuum out and isn't sealing properly. Can't see why it went when I was working on another part of the engine, but I'm convinced it is the culprit. I disconnected the brake vacuum takeoff and connected the varoram pipework to that and it held vacuum. I've had to remove the whole varioram system which is now on the bench and tomorrow I'll order a new valve.

I did check the vacuum tank that you mention by isolating it and subjecting it to some positive pressure which it held. I never would have figured that the valve had failed if I didn't have the vacuum guage permanately connected.

Porsche in the UK rarely keep things like this in stock so I'll have to wait a few days for it.

Thanks again for your input, as as always very knowlegable.

Regards
Tal

shamrock

Hi there Guards,
when I saw the title I was very interested , purely cos I know very little about the system , especially the vacuum workings and I need to figure more for when my system goes on the blink (in fact I'm not even sure that it's working properly at the moment )
Is there any chance you could post some pics as you're putting the hoses back together again?

Toga

+1

targagr

hey guards red,

can you pls post the part # for the check valve...Thanks!!

guards red

Hi fellas,

got the whole thing sitting on the bench waiting for the parts at present. Will post pics of the workings, will also post the part numbers for the things i replace. One of the venturi tubes is an older version on mine so that's going too. Not done the photo DIY before, so bear with me as I'm a computer idiot.

Regards
GR

alex973

very intersting, here is a v-ram diagram, i got this from Bill, good luck..

http://forums.pelicanparts.com/uploa...1207935592.gif
http://forums.pelicanparts.com/uploa...1207935613.gif

993MAN

Well that's a piece of cake to follow!