MGB MGB clutch slave bleed driving me nuts

[wkilleffer]

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

 

[bobhustead]

The inlet hole and bleeder hole are usually a different shape at the bottom. Tapered seat on bleeder hole. Bleeder must be on top of cylinder as air in a cylinder rises. Get a clear glass vessel and fill it part up with fluid. Put one end of a clear plastic or neoprene hose on the bleeder outlet. Must fit tight. Put the other end of the hose in the vessel you put fluid in and put it on the floor in sight. open the bleeder slightly. Pump the pedal slowly and watch for air bubbles to stop coming out of the hose. Every 5 or so pumps, check level in your master reservoir.
Bob

 

[bobhustead]

Someone on this forum (CJD, I think) has suggested on clutches just opening the bleeder and waiting.
Bob

 

[wkilleffer]

I did that thing in the Moss video where they push the pushrod back into the slave. Saw some bubbles for sure. Did it more than once. Also, pushed the pedal down with a piece of wood, wedged it down, and then opened the bleed screw. Did that a few times, and saw some bubbles again. I'm practically sweating brake fluid. The last time I did that wedge and open the screw thing, I'm pretty sure the fluid in the hose was running clear and bubble-free. I'm feeling pressure at the pedal, but it's not enough to allow it to disengage and go into gear. The clevis pin down at the fork shows some wear, so maybe next step is to replace it and the one at the pedal?

Really hoped to have the car operational today. I'm frustrated, SO is mad because this got me kind of tunnel visioned and I messed up our evening plans. Hard not to think that this would be less of an issue with a longer hose and swapping the inlet and bleed ports. Don't know, though. The Jaguar guys all say this is an issue with them, too.

 

[JPSmit]

sorry this isn't working.

three thoughts

1. I am having a tough time visualizing your setup but, as I read your description, shouldn't the bleed screw be above the inlet? What I am visualizing is that the bleed screw has to be at the highest point in the MC or SC to let the air out?

2. MG Midget 1500 owner here (full disclosure) so I don't know how the MGB differs, but, I chased a soft clutch pedal for a season before I realized that the tolerances on my new line were so bad that they would not seal no matter what I did. Retrieved my old line and all was well.

3. Is any part of the clutch line higher than the MC? On Midget 1500's it is almost impossible to get that last air out as the line is higher than the MC. The easiest way I have found is to disconnect the MC, raise it higher than the line - pump it to remover the air and then reconnect everything.

Not sure how it translates but you can't be far off - good luck!

 

[wkilleffer]

sorry this isn't working.

three thoughts

1. I am having a tough time visualizing your setup but, as I read your description, shouldn't the bleed screw be above the inlet? What I am visualizing is that the bleed screw has to be at the highest point in the MC or SC to let the air out?

2. MG Midget 1500 owner here (full disclosure) so I don't know how the MGB differs, but, I chased a soft clutch pedal for a season before I realized that the tolerances on my new line were so bad that they would not seal no matter what I did. Retrieved my old line and all was well.

3. Is any part of the clutch line higher than the MC? On Midget 1500's it is almost impossible to get that last air out as the line is higher than the MC. The easiest way I have found is to disconnect the MC, raise it higher than the line - pump it to remover the air and then reconnect everything.

Not sure how it translates but you can't be far off - good luck!

These are the times that try men's souls...

As to #1, I am getting a great deal of feedback which would indicate that the bleed screw should be at the top and the inlet at the bottom, but the included hose isn't long enough for that. Moss included some kind of note in the package stating that their vendor was putting the bleed screw and the plug into the wrong holes. Believe me, I tried to do it the other way, but it kinks the hose.

As to #3, pretty sure nothing's higher than the MC, but I'll have another look tomorrow.

 

[mezy]

If as you say the bleed nipple it below the inlet flexi hose and cannot be reversed then your gonna struggle to get all the air out of the
slave cylinder. unbolt the cylinder, push the piston into the cylinder as far as it will go and clamp it in. then with the nipple uppermost
bleed it with your one man bleed bottle, then re fit the slave,

 

[JPSmit]

If as you say the bleed nipple it below the inlet flexi hose and cannot be reversed then your gonna struggle to get all the air out of the
slave cylinder. unbolt the cylinder, push the piston into the cylinder as far as it will go and clamp it in. then with the nipple uppermost
bleed it with your one man bleed bottle, then re fit the slave,

My thoughts exactly - you will never get the air out otherwise. If you can take the slave off and hang it down under the car, the air should <should> flow up the line.

Having said that you might want to pause at this moment and get a proper line made/ ordered. If you want to get the car going for the rest of the season go for it but, this is going to p*ss you off forever and make everything more complicated.

Can you recycle the short on in the meantime?

 

[bobhustead]

"Perhaps the laws of physics cease to exist on your stove" - Vinny Gambini

Regardless of the BS from Moss that accompanied a badly manufactered part or how many things you might try or refuse to try, or the sincerest hopes, if the bleeder is not above the mass of fluid in the slave, the air is not coming out of the slave thru the bleeder. Period. And the bleeder has to be in the designed bleeder hole to make the bleeder work as designed. We are not saying that there is not also another problem, but this is not going to work regardless of other conditions unless the bleeder is adjacent to the air pocket.
Bob

 

[mezy]

You state that you tried fitting the pipe in the correct hole (bottom) but it kinked the pipe,
Can you not make up a short pipe fronm flexi to bottom hole, then the nipple can go in the top where it belongs.

 

[Joe Reed]

FWIW, the reason the bleeder is delivered in the wrong hole is for packaging. It won't fit in the box if the bleeder is in the correct, upper hole. It's been this way for years. I suppose using a slighter larger box for the part is just out of the question

 

[bobhustead]

Joe
Wm. posted that Moss included a writing with the cylinder that a fit problem, not just a shipping convenience problem.
Bob

 

[bobhustead]

On the moss site, there are 2 product photos and a schematic, all of which picture the cylinder assembly in what looks to be the workable configuration.
Bob

 

[wkilleffer]

Here’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.

 

[bobhustead]

The hose is where it belongs. Did you replace the flex hose or disconnect any other joints besides the master? Didyou use a tube (flare) wrench to make sure you got good tightening on the fittings into the master? I really suggest you use the hose from bleeder into a brake fluid bath as I suggested.
Bob

 

[YakkoWarner]

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.

 

[bobhustead]

Yakko
Wm has a copper washer on the joint.
Bob

 

[wkilleffer]

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.

Even wrapping teflon tape around the threads?

 

[wkilleffer]

The hose is where it belongs. Did you replace the flex hose or disconnect any other joints besides the master? Didyou use a tube (flare) wrench to make sure you got good tightening on the fittings into the master? I really suggest you use the hose from bleeder into a brake fluid bath as I suggested.
Bob

I replaced the MC, the hose, and the SC. Now, pardon my ignorance, but when you say "flare wrench" you're talking about those wrenches where the wrench goes almost all the way around the nut or bolt? If so, no, I didn't, but I have a set and can have another go with them.

I'm getting pressure, but it doesn't seem to be happening high enough in the pedal's travel to make the clutch disengage. The clevis pin may have enough wear to aggravate the situation.

 

[bobhustead]

Those are the wrenches. You don't need 100 ft/lb, but needs to be good and snug. I found one I didn't get tight enough on my TR3 last year. When your system is at rest, how much free play can you feel if you grab the throwout fork end at the slave pushrod and move it back and forth?
Bob