Clutch Slave Cylinder dribble...

[Boink]

I'm hoping this is easy.

My Bugeye (with 1275, ribcase but otherwise all else "original" - including a new clutch) started to be fussy getting in/out of gear... and this came on rather fast. I was nearly stranded but pumped the peddle a bit and limped home.

Upon inspection, the fluid in the single square reservoir was down a bit (though not bad - and the brakes were fine), and there was no obvious leaking at the clutch master (or lines)).

Under the car the slave looked OK (at first), but I then noticed a single drop of fluid near the push-rod. When I squished the rubber boot inward a bit, out came a dribble of hydraulic fluid. :frown: It was incontinent!

Question: figuring duct-tape is out of the question :laugh: , can I easily swap out the guts (with a repair kit) WITHOUT removing the slave unit itself? Maybe I should pull the entire thing and evaluate the cylinder wall (and possibly hone it). Any tricks other than a pesky bleeding process at the end? Also, I notice that Moss mentions a different repair kit for a 948/1098 vs. 1275. I've got a 1275 but I think it's the original (square) combined master cylinder. Do I get the original for the 948/1098? https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=36484 (part #36 - but two are listed) I suppose I should just crawl back under there and see how the cylinder looks (bleed screw configuration - to see whether it's a 1275 or the 948/1098 style - right?).
Thanks.

 

[nomad]

The 1275 slave has a rubber hose connection while the 1098 and 948 have a steel line connection. Personally I would remove the cylinder and hone it a bit before fitting new rubber to it.

I'm using the 3/4 bore master on cars with front disc's. Do you know what MC you have? I believe it will determine what size slave you should run. Though if you're happy with your clutch then what you have is fine.

Kurt.

 

[Gerard]

The 1275 slave has a rubber hose connection while the 1098 and 948 have a steel line connection. Personally I would remove the cylinder and hone it a bit before fitting new rubber to it.

I'm using the 3/4 bore master on cars with front disc's. Do you know what MC you have? I believe it will determine what size slave you should run. Though if you're happy with your clutch then what you have is fine.

Kurt.

Mark,

Ditto on the remove, inspect and hone. The 1275 slave is a 1 inch bore and <span style="font-style: italic">does not</span> use a circlip to hold the piston in the bore, and as Kurt mentioned uses a rubber flex line and larger fittings. The 7/8" slave bore will have a circlip retaining the piston.

You probably have the original slave from the Bugeye, but MC bore won't really matter. You can use it with either 3/4" or 7/8" master cylinder. It does actually work better with the 3/4" bore MC.

 

[Guest]

X3, pull and at least take a peek. No sense in new parts without honing.

 

[Boink]

Thanks guys. Great advice, and thanks with the identification of the slave.
If I know MCs, mine is the original 7/8" (and have a change in that on the back burner because I DO have disc brakes)... but just want to get it back on the road ASAP (given the weather is so good). I'm pretty sure it's an original slave - but should know shortly as I'll pull it out today and have a look.

Gerard, I know you offer a MC switch to a 3/4". When I do get around to doing that, will I then be better off changing out the slave? And what do you think about the much less expensive after-market slaves?
Thanks.

 

[Gerard]

Gerard, I know you offer a MC switch to a 3/4". When I do get around to doing that, will I then be better off changing out the slave? And what do you think about the much less expensive after-market slaves?
Thanks.

Mark,

You can continue to use the same slave. All the reports I get are that the clutch works better when going to the smaller bore MC. You can switch to the 1" slave if you like, but it's not as straight forward to swap since the clutch line used is a larger diameter and hence uses a 3/8" fitting rather than a 5/16". You also need to add a mounting plate where the flex line and hard line join. Then there is the original size fitting at the MC, so an adapter is needed somewhere for that. Some people make up a full length braided line with the correct fittings at each end, but that's not cheap either.

As far as as the aftermarket MC's, there's not much complexity to them, so I would think they'd be fine as long as the metal doesn't corrode in a hurry and the seal is of decent quality. I can also have your original slave brass sleeved, which would make it virtually trouble free forever. It costs about the same as a new one.

 

[nomad]

I brazed a tube fitting to a old 1275 hose end so that I could use the 1275 slave on my BE. Cheeep here!!

Kurt.

 

[Jim_Gruber]

I took the angle grinder to my Smooth Case so I could use the 1275 Slave. It was 12 years ago but been working well ever since. I can't remeber exactly what I did as he 1275 Slave would not fit in there straight. I was able to grind something away on the tranny flange or slave to make it fit. And I did it without pulling the tranny. That was the trick part.

 

[lbcfan]

Mark-

When I went to a 1275 and ribcase for my bugeye I found the clutch pedal pressure uncomfortably high. The smaller bore master for the clutch solves that completely, and Gerard's rebuilt MC has worked great.

I'm using the 948 slave. As some do I also ran the slave cylinder bleed via a brake line to a location in the engine compartment. Beats crawling into the passenger compartment to bleed the slave.

Good luck.

 

[JOeyKnapp]

LBCfan, do you have a picture of the routing for the bleed line?

 

[Gerard]

Joey,

Nothing tricky about the routing. Bring it up by the battery tray or all the way over to be near the master cylinder.

Here's what I did on my '68 so I could use a short piece of hose to return to the reservoir, but you wouldn't want to do that on the tandem/combined MC.

Slave line

 

[Boink]

Well, just a quick report back. I was planning on ordering some bits when a friend of mine turned out to have a spare (NEW) 948/1098 slave available... which has all the guts too. It was exactly like mine.

So, I pulled the old one and installed the new one. Easy work. Shouldn't have taken more than an hour (and I thought it was going SO well). However, the bleeding operation is not going well as when I'm "done" I seem to have a slave piston that only moves about 1/4" (which isn't nearly enough).

Funny story. <span style="font-weight: bold">I'm having my wife depress the peddle so I can do the bleed. I'm getting nowhere so I climb out to look at the master and have her depress the clutch... and no movement! Aack. So, I kindly ask her "which peddle are you depressing?" Turns out that she'd been methodically depressing the GAS peddle!!! I now think I have a modest amount of air in the system.</span>

Seems to me that the slave internal spring is pushing the piston out pretty far... as it drifts way out all by itself. Then, depressing the clutch only pushes it another small bit (and certainly not enough).

So, I may have to start over with this pesky bleeding operation. Man, the bleed fitting is in a lousy place. Who designed this? :laugh:

EDIT: wish I'd seen this video before I started... https://www.youtube.com/watch?v=uj1dMdYgRK4 as this will surely resolve the matter. I was trying to push that piston in while it was attached to the clutch fork!

 

[lbcfan]

Joey-

Gerard's solution was better than mine. I used a line that was a little short, but still better than none..

https://s1355.photobucket.com/albums/q702/michaelandaudrey/

 

[JOeyKnapp]

Thanks for the pictures, guys! I will have to do that when my time comes!

 

[regularman]

You might get lucky with a brake hone run through it and a new kit. Otherwise I think new slaves are not that bad.

 

[Boink]

I put an aftermarket slave in and it definitely doesn't leak.

But here's an interesting factoid for some of you. I've read that if you have a non-circlip slave it is 1" and if you have the circlip it's 7/8". However, I'm living proof that this isn't true. My old slave is exactly 7/8" with no circlip (and even the old rubber cup as a 7/8" on it - and for the record, there is no groove for a circlip so it doesn't wouldn't receive one). So, maybe the circlip is a function more of vintage. I sort of like the newer one with circlip as it stops the plunger from falling out.

Next interesting observation. The slave I removed, which is leaky, had a perfectly healthy-looking rubber bit on the end of the piston. The cylinder was fairly polished. Wouldn't thought it would have leaked so easily under those conditions, but maybe honing would resolve that. Odd.

 

[Gerard]

Mark,

If your old slave does not have a circlip, I would suggest it is not OEM. I personally have not seen one without, but every one I have seen has been an OEM one. Given the 50 years plus, yours could have easily been replaced once or even twice.

Regarding the old seal looking good, if the lip has lost it's springiness or just worn below tolerance, it entirely possible it would still leak. There is a tolerance for seal OD vs bore diameter, and I have on occasion even had brand new seals that are outside acceptable tolerance range and failed immediately.

 

[Boink]

Mark,

If your old slave does not have a circlip, I would suggest it is not OEM. I personally have not seen one without, but every one I have seen has been an OEM one. Given the 50 years plus, yours could have easily been replaced once or even twice.

Regarding the old seal looking good, if the lip has lost it's springiness or just worn below tolerance, it entirely possible it would still leak. There is a tolerance for seal OD vs bore diameter, and I have on occasion even had brand new seals that are outside acceptable tolerance range and failed immediately.

Thanks Gerard. Makes a lot of sense. The rubber edge isn't super springy at all and I suspect it's not original either (as the internal pieces just looked too recent). Thankfully, the new (aftermarket - nonLockheed) slave unit that a friend had in his stock of spare bits seals well (at least for now).

 

[Boink]

Follow-up question:
I've put the new after-market slave in (7/8" which is what I had and worked) but realize that the prior owner used a 2 and 3/8" push-rod that has its tip nearly out of the slave when fully extended (and I think my release bearing is fine).
Wondering if it would be better to go to the 2 and 11/16" long one so-as to have the tip deeper in the slave when operating.

In the attached photo (PRIOR to replacement), I now realize that the pushrod is barely in the chamber... and with full extension, might be nearly OUT (after about a 1/2" throw).
Thoughts? Thanks.

EDIT: Oh, one more. I purchased the rubber boot that is supposed to go on the lever arm, and wow is it tough to get its tiny hole over that fork for the clevis pin. Is there a trick (short of sliting it and zip-tieing back)?

EDIT #2: Just an informational thing. The after-market (non-Lockheed) 7/8" bore slave from Moss does <span style="text-decoration: underline">not</span> have the circlip (so the one I took out was likely the same one).

 

[Gerard]

Follow-up question:
Wondering if it would be better to go to the 2 and 11/16" long one so-as to have the tip deeper in the slave when operating.

EDIT: Oh, one more. I purchased the rubber boot that is supposed to go on the lever arm, and wow is it tough to get its tiny hole over that fork for the clevis pin. Is there a trick (short of sliting it and zip-tieing back)?

Mark,

Easy question first, use a good rubber lube or any of the slippery vinyl or rubber restoration products. I like the Black Magic brand products.

On the pushrod issue, it would be good to know you have the correct fork on this gearbox and that it's not bent. I realize that may be difficult to answer. What about all the pivot point, including the one inside the bell housing. If you have the pushrod removed, you should be able to get a feel for how much slop the is the the fork pivot bushing. Check all the other pivot points, both for oval holes and worn clevis pins from the pedal box the the gearbox.

The pushrod you have should be correct, but of everything else checks out, you could try the longer one, but my guess is it's a fork issue.