robot808

I know that there are a million plus threads on this subject, I was hoping that someone experienced these same symptoms.
I have recently rebuilt my clutch master and slave. After weeks of bleeding, I am experiencing the same conditions:
After bleeding the clutch it works better than ever for one day.
The next day the pedal is loose for an inch or two before you feel any pressure and I cannot shift.
I use a powerbleeder, I have bled thru the Master (Kempf method) I pump the slave rod, and even use the old fashioned pumping the pedal and alternatively opening and closing the bleeder screw.
Any ideas?
Thanks,

Mitch Johnson

Are you sure there aren't any leaks between the master and slave? Seems like the only place that air could get introduced assuming that it was fully bled.

robot808

Thanks Mitch,
I have looked over the line every time I have been under there (which is alot by bow) and I have found no leaks anywhere.

Tom. M

When you do the Kempf method, does air come out? If so..it's getting in there somewhere..

Ispeed

I have the same cr@p going on too. New master guts, flexible hose, slave cyl. I have to dig deeper for a leak...

robot808

Tom,
The first time I did it (Kempf method) air came out. The next 3 or 4 times I did not notice any at all.
Can anyone explain to me why it is while the car is parked that the problem seems to set in? I have only a very basic understanding of hydraulics, but it seems to me that air would really be introduced while the you were using the system. My car runs fine for a full day. Even when I park, it works great. It is after it sits a while that it acts up. I would understand if it were dripping fluid, but there are no signs of leaks at the MC, slave, or at any lines.
Thanks again,

mark kibort

unless the temperature builds up and expands the air you do have in the system.
we are having this exact same issue with scots car. havent done anything but push the rod back in the clutch slave, but bleeding is next. then, if we still have issues, i guess the clutch master guts have to be replaced. ( 928intl trick of buying a new master, but only replaceing the guts on the existing clutch master body )

mk

robot808

Mark,
The gut replacement is exactly what I just did. I feel confident in it. The guts felt flush with the inside diameter of the cylinder. I believe that part worked well.
The only bleeding method I haven't tried is the one with a jumper from the slave to to the brake. It seems like a solid method, but also seems similar to the effect of pushing on the slave rod.
Any thoughts?

Mrmerlin

Replace the clutch master and slave remove the whole system from the car read this post search for another way to bleed the clutch hydrauics,this one works and you only have to do it once

Mrmerlin

https://rennlist.com/forums/showthre...tch+hydraulics
go here

jpNcos

Hey Bob,

I know you were helping me out when I was having my issues. You mentioned that you replaced the master internals. The thing that was giving me problems was the length of the pushrod. Somewhere on here there is mention of different size pushrods floating around and some are shorter then others. I ended up using one from a 79 because it is adjustable.

Not sure if this will help you but something different to look at and since I have an 82 5-speed thought I'd throw out my 2 cents.

nosnow

There is a specific adjustment for all years on the pushrod. If the pushrod is not properly adjusted hydrolic fluid will not move freely between the resovoir and the master. Eventually the system needs to be re-bled. I don't have time right now but I know there is already a thread on this. I suggest making sure the push rod (rod connected to clutch pedal and the master) is properly adjusted per specification.

Lizard928

I honestly believe that the clutch master is the main problem in the factory clutch system, I ended up using a floor mount wilwood master system.

Not for the purest, but it works a million times better, and bleeding was a piece of cake.

robot808

Mrmerlin,
I am going to give quick fixes, just a couple more tries. If I don't have any luck, I am sure I will use your write up. Thanks for that.
jpNcos & nosnow, help me understand. If the pushrod is too long it pushes the master in too far? Does this let air in somehow?
I will check the length tonight.
Thanks again,

nosnow

Verify the clutch preload proceedure. I had simular problems with the cluch going bad after ~30 minutes or after a long drive w/no shifting. I adjusted the preload and the problem was fixed.

Scott with username hupp did the following writeup recently.
I agree with some of the others -- sounds like you have a air in the system. Avoid letting crazy creative solutions creep into your head at this point because these systems are quite simple and it's usually a simple thing causing problems.

Take a deep breath the start from step one (assuming you have the oem parts in the car).

--Remove the pedal rod at the clutch pedal.
--Bleed the clutch again.
--Remove slave from the bell with lines attached and with bleeder closed, slowly push the slave rod in until it reaches its stop. Slowly release -- then repeat this multiple times. This is done to force the last remaining air pocket in the master back to the reservoir. AND turst me, this air pocket will be there no matter how long you bleed.
--Install slave.
--Install pedal rod with correct pre-load or lack of pre-load (as mark mentioned 1mm gap) depending MY. The rod length can be adjusted by loosening the lock nut and then turnung the rod in the appropriate direction to lengthen or shorten. This is an important step and what you described previously as the clutch getting worse after 30 min sounds as if this rod adjustment is not correct. Too much pre-load causes the master piston to sit too far forward. This blocks the ports that allow the clutch/brake fluid to flow freely as the clutch is used and you essentially pump more air in with each use.

On the mechanical side of things:..........
__________________
Scott
1979 928 5-Speed, LSD
Kiln Red