Fronkenstein

I swapped in a 10 inch booster. But I am baffled as to how that affects the clutch master and slave cylinders. We have pressure and vacuum bleed the system 3 times now. That booster is operating 4 monobloc Cayman S calipers with ease.

I think I need to measure the throw at the rod (17.4mm) and where the release arm is shooting in the inspection hole for starters. As well as check the H adjustors - again and inspect the short shaft.

Thanks,

Fronkenstein

Fronkenstein

You're right Erik. And it was in the 80's ;-D

Fronkenstein

hacker-pschorr

So now we have fallen down the rabbit hole of intermittent clutch operation?

I had similar problems, the clutch would only act up after the car was warmed up.

After a dozen or so clutch removals trying various parts, this was the problem:
https://rennlist.com/forums/928-foru...2=#post3145762

Since I kept re-using the same pressure plate (with the bearing installed) with other parts (4-5 intermediate discs for starters) I did not detect the problem until I finally decided to install a new release bearing.

This was allowing the bearing to **** itself in the pressure plate causing the clutch to drag.

No idea if this is your problem, just one more item to keep in the back of your head. That "tooth" which is broken in the photo above, I broke another one shortly after replacing the bearing. Knock on wood the last one has held up but I talked to Turbo Todd about making a stronger one if I ever break it again.

Dave928S

It doesn't ... the only connection is that the clutch master gets its fluid from the brake master reservoir via the notorious blue hose.

James Bailey

booster would have nothing to do with clutch operation.....
There is the need to modify the now common replacement clutch master cylinder to allow a longer stroke......well documented here.
Have also seen several "extended" slave push rods on some cars that were dismantled...

The Deputy

Sorry, l know this is no time to be cruel...but l couldn't resist...lol

However, in my defense...we only got to go for a seventeen second ride in the vidoe in the other trans post...and there were no donuts involved...

Brian.

Rob Edwards

Yes, ignore my brainfart post from last night, dunno what I was thinking about.

Fronkenstein

Brian,

Not gonna drive it much until I know it's right. When clutch engagement is 40mm of the floor something is wrong. As you can see from this thread I've got way to much time invested to blow it up now

Fronkenstein

Fronkenstein

James,

Ah what do you mean "modify... the master cylinder"? And please provide a link so it can be documented here.

Fronkenstein

Dave928S

Here's a link to a thread on that issue ... https://rennlist.com/forums/928-foru...e-old-one.html

This would certainly explain your problem, but I'm not sure that this could be the case as you haven't changed the master have you?

Stan and a few others also note, in that thread, that brake master size has a bearing on ease of clutch master removal, which explains Robs brainfart and me remembering some vague relevance .... could also be early onset alzheimers

Fronkenstein

Yes, everything has been either replaced or rebuilt from engine to transaxle. Including all hydraulics.

I am really unhappy about this "mod". How stupid is this? And why isn't there a "Red Letter" in the box saying "READ THIS FIRST!!!"? There is nothing in the box.

So I have no idea how much this is going to suck done I replaced the 9 inch with a 10 inch booster while the engine was out.

Getting the 10 inch booster in was bad enough. Do you think it's possible that the master can be dismantled under the dash?

One other thing is it doesn't feel to me like the pedal bottoms out. It goes almost to the carpet.

Please tell me there is another way - puh-lease!

Fronkenstein

Fronkenstein

Oh and for the record Deputy - I would sooner burn Inga to the ground than put a slush box under her

Fronkenstein

Fronkenstein

So after reading much clutch master cylinder pain and suffering by the brethren, I am seriously considering the "fender well modification.

After all the 928 is not a monocoque design so I can't imagine that cutting a nice clean uniform access hole will compromise the structural integrity of the car. And I plan on flanging the opening and using a fuel pump access plate from a BMW or Volvo as the cover.

Anyone car to chime in regarding my assumptions on the structural issues? This car will never be original and its not visible just as all the other mods are not visible with exception to the Cayman S calipers and rotors.

Fronkenstein

James Bailey

You need NOT remove the master cylinder just pull the guts out from inside the cabin...shorten the end of the plunger and spring.....and put it back together...

Fronkenstein

Thank gawd I s hoping you'd say that. It's been 6 months since I did the booster and master change out and couldn't remember if the opening was large enough to pull the guts.

Thanks for confirming James!

Fronkenstein