Bleeding clutch!

I've been following the brake bleeding thread in the hope I could pick up some tips, but I'm still having a problem with my clutch.

I've tried to bleed the clutch, but it's not operating. Are there any 'gotchas' I should be looking for?

I don't think it's possible to fit the slave cylinder with the rod from the release arm not correctly located against the slave cylinder. But could I have got something badly aligned?

I have fluid. I don't think I've got any leaks, as the fluid level isn'r dropping (when the bleed valve is closed, of course).

I've set the pedal height and got my 1.5mm slack on the operating rod on the master cylinder before the cylinder operates, so I think that's all good.

But when I press the pedal, I feel an increasing amount of resistance as the pedal moved down, but it does eventually hit the floor without disengaging the clutch (checked by turning the engine over with it in gear, and the torque built up in the transmission isn't released enough to easily get it out of gear, when pressing the pedal. It feels like it's doing something, but I don't have enough travel to actually operate the clutch.

I've tried manually bleeding with someone on the pedal, while I open/close the bleed valve, I've tried a 'vacuum' bleeder that connects to a compressor, which pulled out lots of bubbles, but I think most were coming from the bleed valve itself. My 'red grease' hasn't arrived yet (as suggested by @rob1miles), so I've not been able to check whether that will help.

Are the Gunson Eezebleed type where it looks like you pressurise the reservoir, any better?

Any other ideas, folks? I'm at a bit of a loss, and am beginning to wonder if I need to take the gearbox out again in case I've done something stupid with the clutch itself.

Thanks!

Have you rebuilt master cylinder, slave cylinder or both?
If not, and even then, could be leaking past the seals.

Stanleysteamer said:

Have you rebuilt master cylinder, slave cylinder or both?
If not, and even then, could be leaking past the seals.

Click to expand...

Both are new...but I think are Britpart (bought them a while ago before I learnt to avoid them!), so that might be my problem! It doesn't feel like the pressure is dropping off if I hold the pedal down (in fact, I've wedged it down tonight, in the hope that this might help).
If it was leaking past the slave cylinder seals, I'd be losing fluid, wouldn't I? I guess it's possible the master could be leaking, but then I'd expect to feel the resistance fade away.

TheMegaMan said:

Both are new...but I think are Britpart (bought them a while ago before I learnt to avoid them!), so that might be my problem! It doesn't feel like the pressure is dropping off if I hold the pedal down (in fact, I've wedged it down tonight, in the hope that this might help).
If it was leaking past the slave cylinder seals, I'd be losing fluid, wouldn't I? I guess it's possible the master could be leaking, but then I'd expect to feel the resistance fade away.

Click to expand...

If the seal is leaking the piston could just be moving through it, it wouldn't leak necessarily.
What packaging was it stored in? Did you check the bores for rust before fitting them?
You said you could eventually push the pedal to the floor. This should be impossible, and does indicate what I suggest.
If the bores are rusty you may get away with honing them. Tool like this. https://www.ebay.co.uk/p/649326269?...MI_-Xc4d256gIVAu7tCh2TzAj9EAQYBSABEgJLDfD_BwE
But you have to hope that the seals haven't come to harm being squisshed past the rust.
There used to be rebuild kits, back in the day. I've done quite a few, but then it stopped and you had to buy new cylinders. Well sometimes!
Much more expensive!

Stanleysteamer said:

If the seal is leaking the piston could just be moving through it, it wouldn't leak necessarily.
What packaging was it stored in? Did you check the bores for rust before fitting them?
You said you could eventually push the pedal to the floor. This should be impossible, and does indicate what I suggest.
If the bores are rusty you may get away with honing them. Tool like this. https://www.ebay.co.uk/p/649326269?...MI_-Xc4d256gIVAu7tCh2TzAj9EAQYBSABEgJLDfD_BwE
But you have to hope that the seals haven't come to harm being squisshed past the rust.
There used to be rebuild kits, back in the day. I've done quite a few, but then it stopped and you had to buy new cylinders. Well sometimes!
Much more expensive!

Click to expand...

Sorry, my stupid, with a clutch of course you would expect to be able to push it to the floor. I was thinking of brakes!
But what I said about leaking seals is still possible.

Have you tried altering the threaded pivot assembly in the pedal box?

Or wedge the pedal down overnight to allow any residual air to rise to the top of the system.

Bleed nipple is at the top yes? Not put the slave on upside down?

Stanleysteamer said:

Sorry, my stupid, with a clutch of course you would expect to be able to push it to the floor. I was thinking of brakes!
But what I said about leaking seals is still possible.

Click to expand...

Yeah, although there isn't a pedal stop under the clutch, so I am worried it's going to knacker the paint if I have to push it to the floor every time! But that's detail to worry about later, when I've got it working.
The cylinders were kept in their bags until I fitted them, but they have been fitted (dry) for a few months, now. But they are alloy, so shouldn't have rusted. Is it likely they've corroded significantly in just 3-4 months? It does seem like I need to remove the system and check the bores carefully. I wish there was a good way to test these in isolation!

flat said:

Have you tried altering the threaded pivot assembly in the pedal box?

Click to expand...

You mean the two nuts on the actuator rod into the master cylinder? Yes, set that up according to the book. If there's other adjustment on the pivot, can you explain what you mean, please?

flat said:

Or wedge the pedal down overnight to allow any residual air to rise to the top of the system.

Click to expand...

I'm trying that now. I won't have an opportunity to check it again until later in the week, thought.

flat said:

Bleed nipple is at the top yes? Not put the slave on upside down?

Click to expand...

Yup, got that right. Annoying that the feed pipe is right in the way when getting to the bleed nipple, though.

Thanks for the suggestions.

Have you tried to bleed the system before attaching to the bell housing?
Sometimes the clutch fork does not push back Enough & leaves a bit of air in the slave.

Hicap phill said:

Have you tried to bleed the system before attaching to the bell housing?
Sometimes the clutch fork does not push back Enough & leaves a bit of air in the slave.

Click to expand...

No, I hadn't. Just undo the slave cylinder and bleed it? Is there a risk the piston will pop out? I guess I use a vacuum bleeder once I've ensured the piston is right in, and not risk actually pressing the pedal...

i was referring to the 2 nuts on the rod so if you have done that then thats all good, try wedging the pedal down over night aswell, sounds daft but i swear it works

flat said:

i was referring to the 2 nuts on the rod so if you have done that then thats all good, try wedging the pedal down over night aswell, sounds daft but i swear it works

Click to expand...

Yeah, thanks. I was careful to ensure I had the slack before the piston operates, in case that was preventing getting the full length of travel or the master cylinder operating correctly. And I tried wedging the pedal down last night and it's still down as I type. I'll see if that make any difference after a couple of days.

Some of the slaves have circlip retainers so they don’t pop out. Check first

I had a similar problem with my Lightweight recently. Eventually found out it was the brand new master cylinder seals that had failed. I also bought myself a reverse bleeding kit to ensure all the air removed from the system. Also found that even though I’d set up the adjustable rod as per manual I had to fiddle with it on the car to get it right. Cut down an old spanner with a grinder to get the one closest to the radiator

Birdbrain said:

I had a similar problem with my Lightweight recently. Eventually found out it was the brand new master cylinder seals that had failed. I also bought myself a reverse bleeding kit to ensure all the air removed from the system. Also found that even though I’d set up the adjustable rod as per manual I had to fiddle with it on the car to get it right. Cut down an old spanner with a grinder to get the one closest to the radiator

Click to expand...

The more I think about it, the more I'm wondering if my new master cylinder is also the cause. Can you clarify what you mean by a reverse bleeding kit, please - something like one of these https://www.ebay.co.uk/itm/312771796795 ?
I've got an extended nut on the front end of the rod, so I'm able to tighten it with a regular spanner. Do you recall what changes you made - did you reduce the 1.5mm of play, or slacken it off further?

Yes, something like that. The problem with my Lightweight was the seals started breaking up. It was a brand new genuine Girling item but the seals had obviously perished. When I took it apart for the third time there were bits of perished seal in the reservoir. I ended up replacing slave cylinder, flexible & metal pipes ( had to cut to get off slave cylinder) before eventually taking master cylinder apart again.

problem with threaded rod in my case was that the pivoting lever rests against a stop bolt at the back of the pedal box. This threads through a little U shaped bracket on the inside of the pedal box. This bear jet had got slightly bent over 40+ years of use so adjustment of threaded rod had to compensate for this. If you get this wrong the valve stem seal won’t seal hole that fluid travels through in master cylinder meaning clutch pedal will move up & down but no hydraulic fluid moving.

OK, thanks. I've ordered one of those in the hope it'll be better than the one I had that runs from a compressor, but I also need to try the red grease trick, as I'm pretty sure I'll still be getting air drawn in through the bleed valve thread, otherwise. I was getting a pretty continuous stream of bubbles when I was using it, before...far more than could possibly be in the pipe/cylinders.

OK, yes, the petal stop is significantly bent on mine, too, but I have adjusted the screw to get the pedal in the '140mm' position, as described, to compensate for the bent stop. And then I set the 1.5mm slack in the threaded rod. I know the seal needs to rest in the correct position when the master cylinder is 'at rest', but I don't know exactly how they are constructed. I assume as long as the threaded rod is adjusted such that there is at least some slack, winding it back any more won't actually help, but I will lose some pedal travel. I was wondering if I needed to adjust it so the master cylinder didn't reach the end of its travel, but I think that would make things worse, even if it did potentially allow the master cylinder to move further.

I can gravity bleed my clutch slave cylinder fix tube to bleed nipple into jar add fluid to resevoir and let it run out the bottom till clear nip up and try.
If your really beat take slave off and hang upside down another to bleed.
Copied this plate idea from another forum but have not needed to use it.
Also altered pedal box to make easier to setup master cylinder.

I always gravity bleed and never any problems, I have also modified the peddle box as Blackburn's video.
Have you looked at the flexible pie that runs down the back of the block ? Have a look whilst someone works the clutch, when the pipe is knackered it will balloon and not allow all the fluid movement to the slave.

OK, I've not even tried gravity bleeding. I didn't think that would be quick enough to flush bubbles out, given they'll be travelling in the opposite direction. I'll give that a go, too.

All pipes are new. Shouldn't have any ballooning, but I'll double check.

There was an option to fit a remote bleed for the clutch cylinder up high.
In the parts catalogue I believe.