MGB MGB clutch slave bleed driving me nuts

[DrEntropy]

View attachment 92282Here’s a photo of my setup thus far. If I move the hose to the hole where the bleeder is, it kinks at both ends and also pulls on it, which can’t be good.

The hose and bleeder are correct in this photo. I've run into the problem on a few B clutch systems, the hydraulics were usually bled with an E-Z--Bleed with no issue. Another "best practices" way is to remove the slave from the trans and clamp the slave cylinder puck all the way in using a socket just small enuff to fit the bore. With bleed screw open slightly and hose fitted, immersing the other end of the hose into a jar with some small amount of fluid, pump the pedal a few times. Close the bleeder and refit the slave to the tranny and stroke the pedal to refill the slave. If that doesn't give enough to fully disengage the clutch there's a mechanical problem someplace. If the clevis pins at either end of the system are worn, replace 'em. If either of the rods have "ovality" to their respective holes, they need replacing. Check the pedal hole where the other pin goes into the rod as well. Those are the "easiest" things to fix in the mechanical linkage. If all that still doesn't give enough fork travel to work the clutch properly, it's in the fork pivot or clutch assembly and the engine/gearbox need to come out.

 

[DrEntropy]

Some of the more extreme examples of pin wear found over years of servicing these cars:

The one far right would "cam" and sometimes work, sometimes not!

 

[wkilleffer]

Here’s the Clovis from down on the gearbox:

 

[bobhustead]

Go ahead and change all clevis pins and examine all the holes they wear on for ovalness, as advised by Doc.
Bob

 

[mezy]

looking at the clevis pin, remember all things wear in both directions so the hole will be just as worn giving twice the amount of free play

 

[bobhustead]

Given different hardnesses, and the fact that the clevis does not spin as much in every hole it bears on, wear of clevis and hole may well not be equal in each part. Note, for example, that the shoulders in Doc's picture are mostly in better shape.
Bob

 

[wkilleffer]

Unfortunately, my efforts to find the Clevis pins locally have been a strike out so far. The local Grainger might have them, but I would have to buy a large quantity. I would be leaving them to friends and family in my will.

Ace Hardware probably came the closest to having the one on the gearbox, but I couldn’t tell if its diameter was right, and it was long enough that I thought it might not work well in the confined space by the gearbox. Tractor Supply was a surprising disappointment. So, guess I’ll order from Moss.

Looks like I may have lost my temper at Moss for no good reason. But when you search online and see what a cluster bomb this task has been for so many people, it’s easy to get confused.

 

[bobhustead]

Amazon. Zoro.
Don't let moss off the hook until it is working.
Bob

 

[wkilleffer]

Amazon. Zoro.
Don't let moss off the hook until it is working.
Bob

Would any of these work?

74 Piece Clevis Pin Assortment

Amazing deals on this 74 Piece Assorted Clevis Pins at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[bobhustead]

I don't know. They are sold by length and diameter. Measure yours. They are likely to be 1/4" diameter.

 

[wkilleffer]

I don't know. They are sold by length and diameter. Measure yours. They are likely to be 1/4" diameter.

I haven’t checked the one at the pedal yet, but this is looking pretty close to 5/16”? The length is an odd thing because it’s hitting 28mm. Neither measurement should be metric, should it?

 

[DrEntropy]

No metric stuff on an MGB. And measure the pin diameter on the cotter pin end. It doesn't get any wear.

 

[JPSmit]

No metric stuff on an MGB. And measure the pin diameter on the cotter pin end. It doesn't get any wear.

and please don't assume it is original (though in fairness it looks like it is)

Can I also say there is nothing wrong with throwing in a short bolt as a temprary fix if it means getting it working.

 

[Jrmandella]

I've got a method I've used on my 75 MGB. I've done it 3 times because i replaced the Slave, Master and Hose on 3 separate occasions. Follow the steps below

BUY THE FOLLOWING
Mitvac tool
Box wrench to open/close the bleed port
Plastic Vet Syringe (just do it. Buy at Petsmart, I'll explain in a moment)
A bit of extra plastic tubing that will bit over the ends of the Mityvac and the vet syringe

Steps
1. Put box wrench on bleed port,
2. Fasten tubing to vet Syringe, fill vet syringe with fluid
3. fasten tubing to bleed port
4. OPen bleed port with box wrench
5. Push fluid into the system
6. Close bleed port
7. Verify the reservoir has a bit more fluid in it

If fluid made it to the reservoir, the lines should be full or fluid but a small bubble remains is in the slave. We'll get rid of it in the next steps

8. MAKE SURE THE BLEED PORT IS CLOSED and the box wrench is on it. Quick timing is the key because you need to open/close with precision
9. Attach the tubing to the bleed port and the MITYIVAC
10. Squeeze the handle on the MItyvac a 4-5 times. Verify vacuum is building up with the little gauge
11. Open the bleed port
12. Watch the fluid flow into the MITYVAC, you should see a couple of big bubbles and then a bunch of soda-fizz bubbles
13. When you see nothing but soda-fizz bubbles, CLOSE THE bleed port

Check the fluid in the reservoir, add a bit of fluid and repeat steps 8-11

THe soda-fizz bubbles are from the air slipping past the bleed port. THey are HARMLESS
I thought the vet syringe was a dumb idea, but it is quick way to reverse-bleed the system and get fluid up in the lines.
Im a software guy, not a professional mechanic. Done this 3 times with success.

 

[Joe Reed]

deleted

 

[wkilleffer]

Update: I got the clutch to work yesterday late afternoon. I used my HF version of the MityVac. You may remember that my OP said I didn't want to use gadgets. Part of the problem is that I bought the HF thing to use with helping to bleed the brakes, and it was very little help, though the ridiculous bleed screws on the new wheel cylinders didn't help. The vacuum pump thing in the HF kit is decent, but most of the rest of it, such as tubes and rubber/plastic fittings, leave some to be desired. I might consider a real MityVac, but only if it's that much better than the HF thing. The problem with some of these gadgets is that they can end up being alot like a get rich quick scheme.

But anyway, clutch works, but the catch point seems pretty low on the pedal's travel. I'm gonna guess that the worn clevis pin could be a factor in that?

 

[bobhustead]

Worn clevis could indeed be at fault.
Bob

 

[Jrmandella]

I have never had good luck with the hose from the bleeder because air always leaks in around the threads, no matter how snugly the hose is fitted to the tip of the bleeder. I had similar problem with a 1984 Jeep - the bleeder was on TOP of the transmission (ended up actually cutting a small hole in the tunnel which was already badly rusted in order to get a socket on the bleeder while pressing the pedal - not a viable option for an MGB).

Opening the bleeder and just letting it trickle thru from the master is messy, but might be the only way to do it solo.

Air bleeding past the threads is normal. WHen you see "soda fizz" in the MityVac Line, close the bleed port. THe bubbles you don't want are the big ones, when those guys pass through, you are done

 

[jr234]

At the risk of asking an FAQ here, here goes... Also, I'm just about angry enough that my normal, erudite and articulate nature may desert me, so hope this makes sense and doesn't go too long...

The car is a 1974 MGB. It recently suffered a clutch hydraulic failure. So, I decided to change out all of the hydraulic parts. I was never all that happy with the master cylinder. It came from a parts company in Knoxville, TN, and among other things, I had to remove the cap on the brake MC in order to remove the cap on the clutch MC. I ordered the MGB clutch hydraulic replacement kit from Moss for around $60. I've done this job before, so it didn't seem all that terrible. Got the MC in place, hooked up to the pedal and the metal line. Working with the pedal box isn't my favorite thing, but it's at least doable.

Now, the slave cylinder had some kind of note with it stating that the inlet and bleed screw might be reversed, and the supplied hose wouldn't be long enough unless the bleed screw were swapped to the other hole. Starting to think that's a bug that Moss is trying to turn into a feature because they screwed up their last batch of clutch hoses. Either way, that puts the bleed screw above the inlet hole. That doesn't seem like a workable thing.

So, got everything in place, clutch cylinder mounted, hose on, pushrod in place and fastened to the clutch fork, and my handy-dandy new one-man brake bleeder. Before anyone asks, this is *not* an Eez-Bleed or anything else that uses some kind of air pressure. It's this: > One-Man Brake Bleeder <
A hose with a one-way valve in it that sticks into a small bottle. Supposed to allow one person to bleed brakes and clutches and the valve keeps air from being drawn back into the system while pumping the pedal. My experience with one in the past is that it works well as long as it's tightly fastened around the bleed nipple. My experience with other more complex gadgets has been a let-down, to say the least...

It's a good thing it's a one-man thing because I live alone and don't have anyone I can enlist for help with this sort of task. If you ever meet me, this might make sense... So, please don't tell me to phone a friend or enlist any help. If it gets done, it's because I do it. I don't have anyone I can call. Not for this, anyway.

Anyhow, I open the screw a bit with the bleed thing hooked on, pump the pedal about 10 times, check the level in the MC, and it's in between the Max and Min. Look in the bleeder, and there's a small amount in the hose and bottle, but it looks like the screw is allowing some fluid to drip out, which probably means air is getting back in.

But that might be a moot point anyway. Starting to find out that it might be all for naught given that the bleed screw is up above the inlet, which may mean it's not going to bleed and air will be trapped inside regardless.

So, what to do now, given that I have myself, hand tools, my one-man bleeder?

Any advice would be appreciate pretty well as long as it doesn't include "go out and buy an Eez-bleed or similar" or "get your friend/neighbor/SO to pump the pedal for you." What I have is what I have, and it needs to be made to work.

Thank you,
-William

I may have the answer for your question about the slave cylinder bleed valve from Moss. I also recently purchased the kit (master and slave cylinders) from Moss, and the instructions about switching the screw to the "top" rather than the "side" position where it was when shipped explained that was simply for fitting the items into the shipping box! Otherwise, the design of the slave cylinder wouldn't fit into the shipping container. I also visited some YouTube videos and a hint was made attach the cylinder part to the "incoming" fluid line to better facilitate the attachment of the final step to the "outgoing" fluid line. You may also want to check out YouTube videos on replacing the master and slave cylinders, if you aren't familiar with the mechanical process (the same boat I am in, not trying to offend your mechanical skills, William). Hope that solves the mystery of the bleed screw transfer procedure.