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Uncomfortable with Clutch Peddle

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RAC68

RAC68

Darth Vader
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After rebuilding the brake and clutch hydraulic systems, I am left with an uncomfortable feeling when working the clutch peddle. Although the clutch master and slave do move freely, the clutch now grabs quite high. After bleeding for the second time, I still have the same high grab. The frustration is that prior to rebuilding all hydraulic components (brakes and clutch) the clutch grabbed smoothly and positively from the middle and now, I have a sense that it may even be slipping a little upon initial contact.

At this point I am left at a loss and looking to tap into the collective intelligence of the Forum for some ideas. Although no bubbles have appeared at the end of the 2 previous Silicon (DOT 5) bleeds, I am wondering if there could still be air trapped in the lines. Peddle resistance seems to be consistent from top to bottom of travel and the slave seems to move quite a distance, however, it is difficult to tell if it is traveling the full extent of its through.

I would appreciate any suggestions.

Thanks,
Ray (64BJ8P1)
 
Hi Ray, if the pushrod is moving "a lot" that's about all you can ask for. Usually I hear that after changing over to DOT 5 the slave cylinder pushrod doesn't operate very much at all.

What's the condition of your clutch?
 
Is the cluch rod attached to the cluch pedal adjustsble???
 
Hi All,

Johnny, I have used DOT 5 for the past 25 years and even after rebuilding the clutch slave recently the clutch action was crisp and caught in the middle of the peddle’s travel. Although not leaking, I decided to rebuild the brake and clutch masters to complete renewing of the full complement of hydraulic components.

Keoke, my peddle rod is not adjustable but it has always seemed to be perfect. I appreciate that, presently, the peddle does activate the slave but grabs at the top of its travel and even seems to slightly slip upon initial application.

My initial thought was that, since the clutch grabbed at the top of the peddle’s travel, maybe I could still have air in the system (even after 2 bleeds). Is my thought logical and possible?

Additionally, since the clutch seems to be ever-so-slightly slipping upon initial application, could the slave be moving the clutch folk further than it should and not releasing crisply?

Any idea on what I should do next?

Thanks all,
Ray (64BJ8P1)
 
I (vaguely) recall a discussion about some pushrods for the clutch slave cyl. that were the wrong length. Did you buy a new S/C?
 
I too converted to dot 5 after doing a complete brake system rebuild, My clutch travel and engagement is the same as before with no problems! Did you bleed the system properly?
 
May sound silly, but were the hose and bleed screw ports inverted? Hose should enter at the bottom and bleed at the top.
 
Bob/Dramboui, this it the original slave and master. It was rebuilt in 1989 and converted to DOT 5. It has been working perfectly since then. Recently, I thought my loss of brake fluid was from the slave and I rebuilt the slave first. The unit was in great condition with no corrosion at all so very easy to rebuild. After reinstalling the slave, all was perfect and it turned out not to be the source of the leak. After rebuilding all slaves, calipers, and booster, the masters were last to be completed. Although the brakes worked perfectly, I seemed to have developed this problem with the clutch.

Nevets, I used the approach described by Keoke and finished off with the plunger-push described in the Moss video. Based upon my previous successes with this process, I was either lucky in the past or doing it correctly.

Thanks for the check Randy. My bleed is on the top and feed on the bottom. Your question is very appropriate as a friend installed the bleed and feed backward resulting in the bleed on the bottom and feed on top.

This seems to be my year for issues. Although all have been the type that can be resolved, the way things re going I may have everything completed just before the first snow.

Thanks all for your inputs as they are appreciated,
Ray (64BJ8P1)
 
I think if you had a lot of air in the system the clutch would engage with a low pedal; i.e. you have to compress the air in the system enough to get the slave cyl moving.

Sounds more like you might have some residual pressure. Did you install a new flexible hose? Have heard of hoses collapsing inside, keeping pressure on pistons.
 
Re: Uncomfortable with Clutch Pedal

I set up the clutch a few months back with dot5 silicone fluid. Because I didn't have very much fluid left and the shops were shut I didn't want to bleed the system so just pumped the slave cylinder all the way out, then pushed it all the way back in. One beer later I had a perfect clutch without losing any fluid.

If your clutch is engaging 'high' then you have possibly just bled out the air that was in the system previously.

To check your slave cylinder push rod clearance, grab the clutch lever and push it all the way forward against the slave cylinder. You should get some movement and there should be some sort of freeplay in the lever afterwards. If there is no freeplay after pushing the lever then your clutch disc is likely worn down. You can shorten up the pushrod to get some freeplay but the disc may be due for replacement.

Andy.
 
Ihad some problems with mine years ago ,so I installed an adjustable push rod and have been a happy camper every since.
 
About 2 months ago, my '65 3000 started showing the same symptoms, high engagement, maybe a little slip, constant feel in pedal from fully depressed to letting up for full engagement, a sort of dead feeling with no feeling of clutch engagement other than when car starts to go. Poster suggested replacing flex hose which I did and it was exactly the same. Mine started doing it all on its own, nothing in the clutch system touched. Tests for worn out facing such as accelerating hard in one gear higher, same going up hill, could not induce slippage. Maybe new form of computer virus, your reading my post infected....
Jay
 
Hi Jay,

You described the condition exactly. Everything works…but something isn’t right. And it all happened suddenly.

Although I intend to install a bleed extension on the slave and re-bleed the system, I am not confident it will change the condition. I would have expected air in the lines to cause the rod to extend less than required and result in a low engagement, however, we seem to have a far greater rod extension that is causing a longer contraction distance resulting in a higher peddle. If the master and slave are the same units prior to rebuild, it seems that the fluid movement, and therefore slave rod extension, should be exactly the same after.

If we move past the hydraulics, could anything within the clutch mechanism have shifted and caused this condition?

Thanks all,
Ray (64BJ8P1)
 
I think Bob may be correct - sounds like some residual pressure. And Keoke may be on the right track asking about adjustable pushrod in the master.
When the pedal is all the way up check to see that there is some freeplay in the pushrod going into the master. If the master piston is not all the way out to it's internal stop, the port to the reservoir will not be open and this might cause residual pressure in the system. Don't know if this could be the problem but I have seen difficulty in bleeding the brakes turn out to be caused by the master piston not going all the way out to it's stop and not allowing fluid from the reservuoir to 'refil' the master when bleeding - sort of the reverse of what you are experiencing. Again, not sure if this could cause your symptoms but worth checking - the factory used shims under the mounting flanges of the masters to insure freeplay, and adjustable pushrods are another way of acomplishing the required freeplay. Pedal should have 1/4 inch or so freeplay before pushing on the piston.
Dave
 
Hi Dave,

I concur with Bob’s evaluation and as I have previously mentioned, I also would had thought air in the system would have resulted in a low peddle grab and not a high peddle clutch engagement. Today I fabricated a bleed extension and re-bled the system. Initially, the Master had difficulty building any resistance with the bleed open, however, after a 5 or 6 pumps resistance built. After tightening the bleed screw, peddle resistance was appropriately high and the slave rod seemed to move fully.

I noted your comment about residual pressure and free-play and not sure if I am interpreting correctly. Following the bleed procedure, I noted that I can lift the peddle another ½” to the end of the its swing. I expect that the Master piston is all the way out and, when pressing, it seems to develop pressure as soon as pressed. Also, can I assume the Master piston is opening the orifice to the reservoir since I needed to bring the up to level during the bleed procedure?

Hopefully, tomorrow I will find if my efforts were successful, however, I am not confident as I have not found anything I would consider wrong….yet.

Thanks to all. I really need the ideas and appreciate the support.

All the best,
Ray (64BJ8P1)
 
Did you just replace the rubber parts or did you hone the inside of the master cylinder as well? No parts flipped on you when rebuilding? For what they cost, I replace with new master cylinders. They come pre-built, the cup size is correct and relief hole clear and open. They are exact match in appearance. They are readily available. Just my opinion.
TH
 
Dave/Jay/All,

I may have worked this problem out, however, it will require the de-installation of the Master and I would like to get some feedback before I do everything that this effort entail…again. I believe Dave and Bob had it correct in that the problem is being caused by residual pressure not being released as access to the reservoir may be happening inconsistently.

This thought started during my last re-bleed when the peddle first had resistance and, after pumping, lost all resistance. A few more pumps and resistance returned but again was lost on the next push. Again, resistance returned and was maintained after a few more pumps.

Also, in the rebuild kit and the picture in the shop manual is a rubber seal called an End-Seal. Although it is no longer provided and used in the Brake Master (pictured in workshop manual too), it was provided and installed in my rebuilt Clutch Master. Since this seal fits over the end of the plunger, it comes in contact with the Dish Washer to produce a buffer when the clutch is released. However, the seal does take up space and may not allow the plunger to sufficiently retreat to allow the opening of the reservoir port. Since it is rubber, the force of the plunger’s contraction may vary sufficiently to allow the port to be open inconsistently.

Before I tare everything apart again, I would appreciate thoughts on the following:
1. Do my thoughts seem plausible?
2. Is this End-Seal still being installed with no difficulty or has it been eliminated on the Clutch Master as it has on the Brake Master?
3. Can anyone see a problem by eliminating the End-Seal in the Clutch Master?

Thanks all and all the best,
Ray (64BJ8P1)
 
In my parts manual, I see a drawing of what I think you're calling the 'end seal,' but it isn't labeled in my manual. I don't think I've ever seen one in either brake or clutch M/Cs, but I could be wrong as I'm working from memory.

The symptoms you described when first pumping up the clutch--'no resistance'--sound like they could be caused by a malfunctioning 'foot valve;' the little spring-loaded valve at the end of the piston that controls flow to/from the reservoir. If it doesn't seal, you'll get exactly the symptoms you describe; if it didn't release, it would hold pressure inside the clutch hydraulics.
 
Quick access to the innards of the master cylinders can be gotten without taking them back out of the car. Detach the rod from the pedal assembly and work inside the car, rebuilding in place. Lessen the fluid by bleeding first. Since it's clean inside, this might save some effort. Good luck,Bob
 
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