924Board.org

[-nick]

I'm having trouble getting into 1st & reverse after putting this new engine together with the 911 alloy pressure plate. I'm hoping there is just some air in the hydraulics that is making the clutch drag. I can only get it into those gears if the trans is cold, and the other gears feel a little more crunchy than usual (G31 trans). I already adjusted the rod on the pedal as far as it will go.

I picked up a mityvac, but have never used one before. I've heard that the clutch pedal should be on the floor / depressed while I'm drawing fluid through. Correct?

Assuming all is working properly, is there a spec for the deflection of the clutch fork arm with the pedal depressed? In other words, measuring the movement of the arm through the inspection window at the bottom of the bellhousing?

ps - clutch master & slave are both pretty new, so I can rule them out as the culprits

Thanks!
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

[Rasta Monsta]

Not really a direct answer to your question, but I used this pressure bleeder for the whole system, and it worked perfectly:



It doesn't seem like there should be any pedal applied, BTW. . .
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Toofah King Bad

• WeiBe (1987 924S 2.5t) - 931 S3

[Smoothie]

I've been looking at the drawing and a real live clutch mc piston and can't come up with a reason to require the pedal to be down while vacuum bleeding. Obviously bleeding the old fashioned way with the pedal you'd pump a few times and hold pressure on it while opening and closing the bleeder, then repeat..

The hydraulic clutch is self-adjusting, so messing with the rod adjustment at the pedal wouldn't help as you noticed. I'd start by getting that set back to where it belongs with 0.5mm space between the rod and master cyl piston (which translates to 3mm at the pedal). No need to be tooo fussy about it - just want it so there's just a bit of space between rod-piston so the piston moves completely back to the end of its' travel when the pedal's released. With the rod set correctly like this, it adjusts itself automatically with a few pumps of the pedal and that results in maximum possible movement of the clutch fork.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[dpw928]

Smoothie,

Just wondering if Porsche made a change to the rod adjustment for the 931 like they did in 1991 for the 928. The change was from .5mm clearance to one revolution of preload. This change was for all model years of the 928. Since both cars essentially use the same parts one would expect a 931 update.

Also, the 928 guys came up with a bleed method that seems to work and eliminates fighting air bubbles that want to rise. It involves removing the pedal rod, removing the circlip and easing the piston out enough to let any air escape. When it stops bubbling, put it back together and adjust the rod. Haven't needed to try it myself though.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[Smoothie]

I remember you mentioning that before Dennis. I don't have any manual updates beyond the 1980 date on mine. It would be a cheap and relatively easy fix, so may be worth a try. Though common sense mechanics is telling me you'd get the absolute max clutch fork movement with both zero clearance and zero preload.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[dpw928]

Smoothie,

Not sure if they changed it due to different parts or just to compensate for wear. I did adjust my 78 928 to preload and it stopped a lot of my reverse to first gear grinding.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

[-nick]

Mityvac is a groovy little tool. It bled the clutch easily - and sucked out a fair bit of air. Not to mention some nasty looking fluid.

Anyone know how much the end of the clutch fork is supposed to move during operation? I got a rough measurement of 5/8" on the inspection hole end. It looks like plenty of movement.

I'm still having some first & reverse grinding trouble. Going to jack up the rear next and feel for the clutch dragging. I put enough pre-load on the pedal adjustment to make the clutch slip under power in high gear and it still doesn't want to go into 1st or reverse at a stop.
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet