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MG MGA - Engaging gear problem after replacing clutch slave

Hi. Replaced the clutch slave cylinder on my 61 Coupe last week and finished off today bleeding it with Ezibleed kit. As far as I can tell I have all the air out. Problem is I can't engage gears, especially when the engine is on. When the engine is off I can engage some gears but not all. Clutch pedal seems good and firm and no leaks. Any steer please on what to investigate first to sort out? Cheers. Tim
Tim Prime

Rod adjust ok at the master cylinder? i.e. not too much slack and therefore not transmitting full movement to the slave.

Steve
Steve Gyles

Steve - thanks for your prompt response. I hadn't thought of that. I'll give it a try. Any guidance on what is the right amount of slack? I attach for info a photo of the worn slave cylinder clutch rod I replaced. There must have been quite a bit of play in it. Thanks again. Tim


Tim Prime

If you grab hold of the push rod in the master cylinder and push it back and forth there should be a slight movement of 0.015 - 0.020" - bit less than a sparking plug gap. If there is no movement you have a slight pre-load on the system which is incorrect. If it is more than specified you may not get enough piston movement in the MC and hence not full movement of the slave cylinder operating rod.

Steve
Steve Gyles

New slave cylinder is shipped with bleed nipple in the end port. The fitting must be relocated to the side port. The end port is for the hose connection. If bleeder is in the end port you can't get the air out.

Watch the slave pushrod while a helper will push the pedal full travel. The slave pushrod should move 1/2-inch, as it takes about 3/8-inch minimum travel for clutch release. If it doesn't move far enough, you still have air in the circuit.
barneymg

Thanks Steve & Barney. The slack is much more than you mention Steve so I'll adjust it. Barney - I had picked up your comments earlier from your website about the right port for the hose so I have that right (see photo). I'll also check the slave pushrod travel once I can get a helper! Really helpful comments - thanks again. I'll let you know how I get on. Tim


TJ Prime

You can delete the banjo fitting on the hose at the slave cylinder. That was used only on very early cars that had two ports on the side of the slave cylinder, so the hose could approach from the end.

These later design cylinders with one port on the end should have the hose screwed directly into the end of the cylinder with a copper sealing washer, no banjo fitting.

The banjo fitting may not affect operation, just looks odd (not needed).
barneymg

Thanks Barney. I did wonder about that when I was installing! Tim
TJ Prime

I had exactly the same problem recently when I replaced my 1600 Master Cylinder. Did all the Easi-bleed thing, then the good lady on the pedal, more bleeding but it was only just possible to engage gears with the clutch release right at the bottom of the pedal travel.Then I found a tip where they were pushing the slave cylinder in the last bit while bleeding it. Which is fine in theory but its all too tight under there for me and I didn't want to fiddle detaching it from the clutch lever.
Solution: Using a piece of 2"x1" timber about a foot long I found I could lever the slave cylinder back in by levering against the front of the floor. As you lever it back, open and close the slave bleed once more. That did it for me. Good luck.
PeteT
PeteT

Mine's just blown the fluid out over the drive (thanks goodness I wasn't miles from home)- so a new slave needed for me too - thanks for all the tips - first time job on the A (did an MGB many years ago) and I've only had it 15 years.
Cam Cunningham

Hi Tim

I am away at present but could possibly pop over sometime from Tuesday if still a problem and you need a second set of hands.

I presume you haven’t joined MGCC but if you are thinking of it and you do so in next week next Sunday is their Scottish MGA Day which I am organising . It is a 90 mile drive from Stirling with 10 other MGA including 2 Twin Cams.

Let me know

Paul
Paul Dean

Steve - your advice was right on the money! The adjustment of the clutch slave push rod on the M/C has sorted it out. Thanks very much. I'll take up the other advice too just to check that all the air is out of the slave cylinder but that will need to wait until Saturday.

Paul - good to hear from you. Sundays are not good for me generally due to church commitments and most of the runs seem to be on Sundays. I may however join up to the MGCC for a year & see how it goes. I'll email you offline about a catch up maybe next week.

Thanks again to all for the advice. The BBS is a first class forum. Tim

Tim Prime

Blimey. Got one right! Glad it's sorted.

Steve
Steve Gyles

If you think you may still have some air in the slave cylinder, here’s a short video from Moss that I have used and it seems to work well.
https://m.youtube.com/watch?v=uj1dMdYgRK4

Jim
JL Cheatham

That's the one Jim that prompted me to try levering the piston back with the bit of 2"x1" timber when the slave is all connected up and in situ.
Pete
PeteT

This thread was discussed between 18/07/2018 and 22/07/2018

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