This is a 2015 M3W with low mileage which has been perfect but recently I noticed the clutch starting to feel "notchy". The pedal descends fine and the clutch and gears work no problem. However, when releasing the clutch I feel a "notch" or stickiness through the pedal. The pedal still seems to return OK but there is a "notch" and a noise like a dull thump.

I removed the inspection hatch above the pedal box to check if the master cylinder had come loose or was binding, but can't see any problem there.

The video below is only 20 seconds and is taken through the hatch, the clutch is on the right. Ignore the squeaking as that's my footwear but you can clearly hear the "thump" which is felt through the pedal.

I've searched the forum and can see some mentions of sticky clutch with people replacing master/slave and even release bearings but I would like to try to pin down the problem before further dismantling.

Any wisdom gratefully received.

Here is the video link :

https://youtu.be/EATssx1ERBY

Does your set up have a clevis pin? I had a similar noise on my 4/4 with the MX-5 transmission and the sound was almost the same. The pin had only a few mm left on it and it was binding.

Thanks,
P

There is a clevis pin at the pedal which you can almost see in the video. Doesn't seem to be any movement there through. In the video you can see that the actuation rod doesn't move when the "thump" occurs so I don't think the problem is there. No idea what the rest of the system looks like so hard to diagnose further down the system, but if there is a similar mechanism at the slave end it could be a wear issue there?

Hoping for some guding wisdom from the forum....

The slave cylinder is usually a concentric type and has no pivots or rods to wear. It sounds like something in the pedal linkage to me, the pivot pins wear like a crankshaft shape and clunk as they move sometimes.

That's useful thank you planenut.

No-one around to help otherwise I would be able to get someone to actuate the pedal and I could feel the joints/pins to see if the noise/notchy thing is coming from there. Might be able to get in closer and video the pins to see if that shows anything.

Does the clutch itself release smoothly? If so it would probably point to a linkage issue rather than a master/slave cylinder.

SOLVED ?

Thanks for the helpful and prompt suggestions.

Yes the clutch works OK and as planenut and Perry_P_M3W had pointed to the pedal/linkage/clevis pin I rechecked this area.

The below video shows that there is some play in the connection between the pedal and the master cylinder input shaft.

Thought I would rotate the pivot for it to work on a different point of the shaft but it doesn't rotate as it has a flat on it. The cotter pin holding the pivot in looks tricky to remove, but if the pin would come out it would be good to check and maybe replace (unless it is the pedal that is worn). As a test I put some lube on the various contact points and it did make a difference.

Anyone experience of changing the pivot pin ?

My car is low mileage so I assume others must be having this issue ?

Here is the video showing the play :

https://youtu.be/zStD9HhNLh8

I used harder stainless replacement clevis pins when I replaced both brake and clutch ones on my Roadster. I also added washers both sides against outer edge of clevis (which should have been there but found missing) to minimise lateral play of pin. Suitably greased with new split pin I expect longer life than OE.

Main reason for wear is lack of lubrication. Suggest regular use of spray grease.

There is the solution of replacing with a unibal ball joint, this requires a bit of work to manufacture a new axle fixed to the pedal.

Hi GLLOQ that looks like a very smart solution !

What size is the uniball joint (I would call it a rose joint) i.e what thread size to match up with the master cyilnder push rod and the diameter of the hole through the middle ?