New slave cylinder failure

Moderators: 330GT, abrent

Post Reply
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

New slave cylinder failure

Post by Jumprun »

As some readers have noticed, I recently did a clutch job on my 1968 330 GTC, just prior to that I had a leaking slave cylinder that I replaced with a new one bought from one of the usual suppliers.
Attached are photos of the failure which shows the sleeve forced out of the housing with the piston and seal. It also appears that the rod was over extended, see in the picture the seal bulging out the side, how is this possible?
After I got my new clutch in, which included a minimum clean-up on the fly wheel and a new ring gear, the release arm was approximately in the middle of the the threaded piston rod when I adjusted the free play to spec, which didn't end up looking like the manual picture, which shows it near the end of the threaded rod, but the clutch was releasing (toward the bottom of the pedal travel) but used more and more of the pedal travel until and got harder and harder culminating with this stuck-on-the-side-of-the-road failure.
Removing the slave was difficult as well because the over extended piston was jamed with the seal and had the clucth jammed in the release position. I guess my cherry was popped with the first Ferrari I needed to flatbed home.

Clues? Ideas? I know I can buy a new slave, but is there something else at play here?
Hmm...maybe when I did the initial adjustment the piston/rod was not all the way retracted? I thought it was, and you would think the spring should have kept it fully retracted, what might cause this?

Thanks and Regards, from Tom in Ca.
Attachments
11157 progress 022.jpg
11157 progress 022.jpg (162.5 KiB) Viewed 11420 times
11157 progress 020.jpg
11157 progress 020.jpg (132.19 KiB) Viewed 11420 times
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: New slave cylinder failure

Post by Jumprun »

I stand corrected about a "sleeve" being forced out, there is no "sleeve" it's just the boot seal groove machined in the body of the slave cylinder, an optical illussion brought on by my ingnorance, so why was the piston forced out?
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: New slave cylinder failure

Post by Jumprun »

What would prevent the slave piston from fully retracting? a miss-adjustment of the pedal plunger at the master? some other problem with the master?
Sorry about the multiple posts, but any advice would be appreciated.

Best Regards, --Tom
User avatar
tyang
Posts: 4060
Joined: Wed Nov 27, 2002 10:28 pm
Location: New York
Contact:

Re: New slave cylinder failure

Post by tyang »

Hi Tom,

The spring in the picture was attached to the clutch fork arm?

Tom
'63 330 America #5053
User avatar
tyang
Posts: 4060
Joined: Wed Nov 27, 2002 10:28 pm
Location: New York
Contact:

Re: New slave cylinder failure

Post by tyang »

It sounds like something is not allowing fluid to return to the Master.

Tom
'63 330 America #5053
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: New slave cylinder failure

Post by Jumprun »

Tom, I believe you are correct, thinking back a few weeks I found quite a bit of clearance between the pedal rod and the master cylinder piston, so not questioning it, I adjusted the excessive clearance out, so maybe the master cylinder was not fully retracting causing the slave to not fully retract?

This is my diagnosis unless someone else has a clue, so I'm going to buy a new master and slave to be sure.

Thanks for the reply, regards from Ca.

--Tom
Steve Meltzer
Posts: 982
Joined: Mon Sep 06, 2004 10:31 am
Location: with Barney the Beagle boy and Enzo 8995

Re: New slave cylinder failure

Post by Steve Meltzer »

Tom, I'm just finishing the replacement of the entire clutch hydraulic system on my GTC. I took Richard Garre's advice and replaced everything....new master cylinder (tho' Karp's can rebuild yours), new high pressure hose (looks like a darn brake hose that should cost $15 but was $85) and a new slave cylinder. The master was so corroded to the firewall assembly from years of slow leaking, that I thought I'd never get it out. When I replaced the slave, I measured the "throw" of the old rod and replicated it with the new one. To get the slave in it's new home, I had to move the clutch fork with a carefully applied crescent wrench.I also protected the high pressure hose with a piece of heater hose shielding it as it crosses the frame on it's way to the slave. All a bit tricky, but will be easier for a real mechanic than it was for a novice like me. steve
steve meltzer,
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: New slave cylinder failure

Post by DWR46 »

Steve: In continuing our clutch discussion, you want to adjust the free play at the master (up under the dash) to about 1/8- 1/4 " at the pedal. You do not need more as all additional play does is reduce the overall clutch disengagement. As long as you have some free play at the master, you are fine, but I like about 1/4" as insurance. This is the play in the pedal with very little resistance.
Then the free play at the slave should be about 1/2-3/4" of additional pedal travel. This is adjusted under the car at the slave cylinder. So you should be able to move the pedal about 1/4" with little resistance, and then an aditional 1/2-3/4" with additonal resistance before you encounter the heavy resistance of the pressure plate itself. Many times I have had to put heavier return springs on the slave as the orignal factory spring would not consistently seat the slave in its bore with the pedal released.

I suspect the writer of the thread has reduced the free play at the master to nothing and as a result, the slave is not fully seating when the pedal is released.
Steve Meltzer
Posts: 982
Joined: Mon Sep 06, 2004 10:31 am
Location: with Barney the Beagle boy and Enzo 8995

Re: New slave cylinder failure

Post by Steve Meltzer »

Dyke, thanx so much for helping me put the finishing touches on the job. There's a return spring (small) under the dash that helps the pedal return to it's full upright position (like the tray table on an airplane!). It's a bear to replace (mine broke) but it's the only thing between me and success. thanx again for your advice. steve
steve meltzer,
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: New slave cylinder failure

Post by DWR46 »

Steve: You are correct, the pedal return spring is strong enough to support a drawbridge!! It is a horrible job to replace without breaking fingers. In the past, I have encountered broken pedal return springs that I just ignored (not proud it it) and the clutch effort did not seem effected. By the way, it is really more than a return spring, it is an assist spring, because once you push it over center, the spring then helps the pedal continue further down and reduces your leg effort. Surprisingly, the only cars I have seen with broken springs are 330 GTC's.
tim
Posts: 341
Joined: Tue Sep 03, 2002 2:48 pm
Location: sacramento, ca

Re: New slave cylinder failure

Post by tim »

Greetings... Somewhere in the recent past, I seem to recall someone mentioning replacing a clutch with a "new improved" design. It was a diaphragm rather than a B&B. Was that you? As diaphragms are thinner than B&B's, I can see nothing but problems. Tim
1964 330GT 5769 -the big yellow taxi 61&66 Morgan +4's Daimler SP250 Turner 950S and some other dull stuff plus a brand Mercedes C300 4matic
Steve Meltzer
Posts: 982
Joined: Mon Sep 06, 2004 10:31 am
Location: with Barney the Beagle boy and Enzo 8995

Re: New slave cylinder failure

Post by Steve Meltzer »

Tim, Dunno nuttin' about any clutch discs nor pressure plates. T'wasn't me. steve
steve meltzer,
"I've spent all of my money on wine, a beautiful woman, and stunning cars. Then, squandered the rest."
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: New slave cylinder failure

Post by Jumprun »

DWR46 wrote:Steve: In continuing our clutch discussion, you want to adjust the free play at the master (up under the dash) to about 1/8- 1/4 " at the pedal. You do not need more as all additional play does is reduce the overall clutch disengagement. As long as you have some free play at the master, you are fine, but I like about 1/4" as insurance. I suspect the writer of the thread has reduced the free play at the master to nothing and as a result, the slave is not fully seating when the pedal is released.

You are correct, I did have the clearance set very close at the master cylinder and pedal rod, my manual shows a specification of around .3mm but I understand your logic. I think I'll put a heavier spring on the slave return also. As a point of reference, my long lower spring at the pedal was broken too.

Thanks and regards, Tom M
DWR46
Posts: 621
Joined: Tue Sep 22, 2009 8:23 pm

Re: New slave cylinder failure

Post by DWR46 »

Jumprun: I think that .3mm between the pushrod and the master piston will translate to about 1/8-1/4" at the pedal.
Jumprun
Posts: 276
Joined: Wed Aug 01, 2012 6:28 pm
Contact:

Re: New slave cylinder failure

Post by Jumprun »

DWR46 wrote:Jumprun: I think that .3mm between the pushrod and the master piston will translate to about 1/8-1/4" at the pedal.
OkI got it, I misundertood your post, I thought you meant 1/4 at the rod.....thanks for the clarification. How did I work on cars before the internet?

--Tom
Post Reply