MGB Register Forum

Hi,
My 1967 mgb has a clutch issue. Last time of driving the clutch was feeling very light and changing gear became harder until the point came where it became stuck in gear.
When stationary and in gear with the clutch pedal fully pressed the clutch is dragging so not fully releasing. Before this the clutch felt perfect at last time of driving
I've checked the hydraulic level which is fine, not had a look underneath yet though. Car had a full clutch about 10 years ago but done very low mileage since unfortunately.
Whats people's idea and how to check myself? Slave cylinder, master cylinder, clutch itself.

Sounds like a hydraulic problem. First thing I would do is get underneath and peel back the dust cover on the slave cylinder. If there is any fluid in there, the slave is leaking. While underneath, you can also check the movement of the push rood when the pedal is depressed by an assistant. It should move about 3/8 to 1/2 inch.

I'm thinking hydraulic also, I'll have a look next week at the slave cylinder and measure its movement

When my clutch showed the same signs, as well as the hose ballooning when the pedal was pressed, the clevis pin and push-rod looked like this. There shouldn't be a groove in the pin, and the hole in the rod started life circular. Easily 5mm of lost movement there alone. Good luck!

Definitely change the flexible if it is ballooning. It shouldnt do that under any circumstances, dont just think of it as a symptom of other parts failing

Sorry for not getting back to this earlier. I've not been able to have a look at this yet as I've been laid out on my back with a sciatica flair up.
If the rod and pin has wear this would be a gradual loss in movement I presume? My clutch operation happened within 30 minutes driving, ballooning pipe I can belive along with failed slave. I may just call RAC out as i have full coverage to see what they say until i have full movement in my back again

James covey wrote: Mon May 19, 2025 8:22 am Sorry for not getting back to this earlier. I've not been able to have a look at this yet as I've been laid out on my back with a sciatica flair up.
If the rod and pin has wear this would be a gradual loss in movement I presume? My clutch operation happened within 30 minutes driving, ballooning pipe I can belive along with failed slave. I may just call RAC out as i have full coverage to see what they say until i have full movement in my back again

How about if the clevis pin, push rod and hose have all aged over time, with the first two wearing incrementally but not enough to be noticed and the hose weakening but not distorting. You're still able to disengage the clutch/get into gear. And then suddenly you can't. If it is indeed 'sudden' it sounds as though the hose might well have been the critical/final change. That's nowhere near the same as saying the hose is the only part in need of attention/replacement.

It's a widespread mistake to think a or b or c is causing a failure, when it's often a and b and c.

Good luck!

Bumpa wrote: Sun May 04, 2025 11:20 am Sounds like a hydraulic problem. First thing I would do is get underneath and peel back the dust cover on the slave cylinder. If there is any fluid in there, the slave is leaking. While underneath, you can also check the movement of the push rood when the pedal is depressed by an assistant. It should move about 3/8 to 1/2 inch.

I think Mike's advice is very sound. A sudden failure looks like a hydraulic seal failure. Whether this is master cylinder or clutch slave cylinder should be fairly easy to determine.
I think you definitely have other bits to sort out as advised, so a thorough overhaul is on the cards.

I have had sudden failures of the clutch hydraulics on a couple of other British Cars, which shall remain nameless! Each time for me it was the seal in the master cylinder.
If you recall, the service advice for these cars back in the day, was to replace all hydraulic seals at regular frequent intervals. No-one seems to do that anymore?

Ian F

Ok so sorry about the slow reply here.
Finally managed to find time to get the car out the garage a couple of weeks ago to look into the problem. Turns out I couldn't find anything wrong, the slave and rubber pipe look virtually new, the master look old though and the clutch started working perfectly again, went for a 15 minute drive and all was well. Confused I was.

Then today I took it out again and all was still well until 20 minutes in and happened again, the problem it seems only happens after a 20 minutes or more which i presume means heat must be a factor causing it to fail.

Any suggestions?

Try changing the hose AND clutch slave cylinder... These are cheap to obtain and will, at least, remove 2 potentials for failure. Is it possible that it was a heat related issue? Changing the clutch plate, etc. is a * of a job as its an engine out job.
To bleed the clutch slave cylinder I disconnect it so it dangles down with the bleed nipple pointing upwards to allow air to be bled easily - with a G clamp stopping the piston from coming out. Leaving it dangling overnight means that any air in the cylinder/hose/pipework (hopefully) goes back up to the master cylinder.
Did you discover what it was in the end?