Lost clutch pedal pressure

Sounds like an issue with the internal seals in the clutch master. If it were leaking past the slave cylinder you would have fluid leaking out around the slave cylinder boot. Maybe someone else has a slightly more concise answer.

Blaine

Daniel:

This sounds like a good opportunity (excuse?) to upgrade your system. Pantera East sells a nice stainless steel long-throw slave cylinder:

http://www.mapenterprises.net/pe/1024x768/main.htm

I think most of the vendors sell nice replacement aluminum master cylinders and stainless steel flex lines. Also, Hall used to sell a very nice billet aluminum mounting bracket with the DeTomaso logo on it for the slave cylinder. Dave Berman has it on his, and it looks very sharp.

Yup, your descent on the slippery slope of endless upgrades may well have begun...

Welcome to the club!

- Peter

I wouldn't suggest a long throw unless it's needed. It increases pedal pressure over the stock clutch slave.
Will

Thanks guys, I will look for the leaks first where
Blaine suggested, but I think your right Peter, it has begun! That said, thats why I love cars. Will, can you or Peter tell me more about the pedal pressure increase? I am very used to high performance firm clutch's, they don't bother me a bit. I definitely want to take the upgrades to this car down the high performance path.
Thanks,

Daniel

You could probably remove the outlet line and cap the outlet port of the master and see if you get pedal pressure. You wouldnt lose too much fluid and you would not have to remove the master cylinder from the car.

Blaine

The main benefit to a long throw cylinder is to improve improve clutch disengagement (the distance between the clutch disc & flywheel) by increasing it from about .020” to .040” or more. For the specifics, I will defer to Jack DeRyke, who has written previously here on the PIBB as follows:

“With an OEM slave attached to an OEM master cylinder, about the best separation of clutch & flywheel you can get is 0.040" as measured thru the bellhousing hole with a feeler gauge (with the engine OFF) This means the clutch disc has 0.020" of clearance on each of its sides- not much to compensate for disc wobble, thermal expansion etc. A long-throw slave will increase the disengagement to about 0.055" More disc separation= less clutch drag on your tranny synchros, which are VERY expensive to replace- upwards of $1500 for each assembly.”

Jack has also pointed out that, “many replacement clutch discs are slightly thicker than the DeTomaso-reworked units that were OEM, so a long-throw slave IS a good idea for ZF longevity regardless of what clutch is in there.”

Back in February of 2006, Jack wrote the following regarding installation of a long throw cylinder:

"With slave cylinder swaps (especially long-throw cylinders), sometimes we
need to move the external bellcrank on the cross-shaft a spline or two so you can
end up with a VERY slight gap before the throwout bearing touches the clutch
fingers. ... In a few cases, moving the bellcrank a spline or two causes
interference with the bellhousing, requiring a bit of grinder-work- see TSB Bull 10,
article 90. Do not be afraid to use the rod & front retaining washer from the
old slave if it results in a better working system, either."

I did not need to do this on my GT5 when I installed my long throw slave cylinder, but it's something to keep in mind.

- Peter

Daniel,
The long throw slave sounds like a good idea. You could install it and if it solves your problem, cool! If the slave is not the problem, then you could tackle the master. Replacing the master is NOT as much fun as replacing the slave. If you have to replace the master, I would highly recommend putting a 2.5" hole on the side of the pedal box to make access to the linkage easier. I will attempt to attach a picture.


Art

This is geat info, thank you. This weekend I will dive into it and see where I stand. My clutch has always felt a little spongy, I was hoping to address it when I install the new engine this winter, didn't make it. Looks like long throw is the ticket..I'll check everything you have all suggested, maybe I'll get lucky and it's just a leak.....Oh wait, I almost forgot, it's a Pantera, it will never be just a leak.
Thanks everyone.
Daniel

Daniel,

Back to your original post which to me indicates air in the hydraulic system i.e. a leak and presumes you had adequate clutch throw previously.

If there is nothing around the slave in the way of fluid (also check under the rubber dust boot) then move to the master cylinder. Check initially from inside under the dash and again remove the dust boot, as the fluid leaks back past the seals. If there is any fluid then your master will require rebuilding or replacing. If nothing then move to the hydraulic lines and look for leaks.

The first upgrade I would recommend as you have to bleed the system anyway is (assuming it is still stock) replace the red plastic line from the hard line to the slave with a SS braided line.

If you do choose to upgrade there are a few variants (bore sizes) on both Master Cylinders and slaves on the market and you want to make sure you match capacities. I have had shifting problems and found I have a nice billet Clutch MC but at 3/4" bore, now the long throw slave is 7/8" so the MC at full travel is only 85% travel on the slave! Wilkinson had the MC and slave on special recently for $70 and $60 respectively.

Good luck,
Julian

Thanks Julian, I let you all know what I find this weekend, again thanks for everyones direction.
Daniel

Finally got to investigate, or basically look for the obvious......yep, puking out the back of the slave cylinder boot as soon as the pedal is depressed.
Pantera east seams to be the item of choice, any last minute advice on which on to choose?
Daniel

quote:

any last minute advice on which on to choose?

long throw SS slave, Marino at Pantera East, ought to do it just fine.

Don't ever let anyone talk you in to an internal (bellhousing) hydraulic throw out bearing - don't ask how I know this, either. It works fine, when it works. But when it doesn't, oh the PAIN!!!

Larry

The SS slave showed up from pantera east, it took maybe 20 min. to install, I have to play with the adjustment still, it doesn't have as much free play as I think it should. I drove it and it operates great, just the pedal is a little to high.
So on my test drive the sun was setting and I discovered, oops, now my headlights don't go up....The joy's of Italian cars. Anyone have a suggestion on this before I dive in. Hopefully this won't take parts I have to wait for.
Daniel
PS Thanks