New clutch master cylinder, can't fit pipe?

[Roy_S]

Well after over an hour of garage yoga upside down in the footwell I got the new clutch master cylinder fitted. But the hydraulic pipe just won't screw in, it is slightly too big to go into the end of the MC.
Tried the old MC and the pipe screws on with no problem at all, but the new one the threaded coupling does not go in far enough the pick up on the threads.
In the pictures you see the end of the coupling is not threaded, this should pass inside of the threads, but it comes into contact with the threads.
Has the size of the coupling changed, do I need a new pipe from the MC to the clutch slave?

[jbuckl]

Should fit as per original. Unless the original isn’t original.

[Roy_S]

I'll take a picture of the old one, looks original to me, but a 44 year old car so who knows....

[sujitroy]

try putting a bolt of the same thread and pitch of the clutch pipe in the cylinder. just a thought

[nigele]

The fitting has probably been overtightened in the past and the flared end has expanded too much. I had this with a new brake master cylinder with the original pipes. You could try reducing the diameter very slightly with a fine file or emery paper if the thread checks out ok.

Nigel

[Roy_S]

I have today ordered a new connecting pipe and to be on the safe side a clutch slave cylinder from SOC where the MC came from.
Measured the internal diameter of the old MC and it is 9.77mm, the new MC is 9.55mm (near as I can measure) so the new one is slightly smaller ID?
Attached pictures of the old MC and also the current pipe fitted, does that all look original? maybe replaced at some point complete with the pipe from a different car?

One thing I noticed on fitting the new MC was on the engine bay side I originally had two nuts fitted onto the MC bolts, the top one (which is a longer bolt) to hold the bracket supporting the reservoir, but not sure why there was one on the lower lug as the MC lugs are threaded.
Anyway the new MC, the lugs must be thicker as there was nothing much of the lower bolt showing to attach the bolt and washer onto, so they are now in the spares box....

[jbuckl]

Nigele explanation sounds fairly likely.... any photos of the flare / union?

[Roy_S]

I'll upload some pictures tomorrow, but I can push the flared pipe into the MC if I pull the union back. Hopefully the new pipe and slave cylinder will arrive tomorrow, but reading the other post some have found these new pipes to be too short.

[jbuckl]

When / if overtightened, the union can swell at the end.
Sounding possibly what’s happened.

[nigele]

It was quite a while ago, but I think it might have been the unthreaded section at the end of the nut rather than the flare on the pipe that had swollen, preventing the thread from engaging.

Nigel

[Roy_S]

That's the issue I have Nigel, I can see the unthreaded section has marks on it where it is catching the threads in the MC and stopping the union being screwed in. Strange thing is the old MC has no such issues, the union goes in without issue and screws in easily by hand.

There is no way that the body of the old MC could have been streatched as it's cast, but as I posted earlier this new MC does seem to have a slightly smaller internal diameter.

Waiting on delivery of the new pipe and slave from SOC, concern is that the new pipes are shorter and end up too near the exhaust now. The slave I've ordered just in case I get issues fitting the new pipe that end. It's like three steps forwards and one step back at times......

[Roy_S]

So the new pipe and slave cylinder from SOC arrived today (great service), and the new pipe fits the new MC.

Did some measurements, and the unthreaded section on the older pipe is smaller than on the new one, so recomend that if you are changing one, be prepared to change the other. The only physical difference between them was the nut size which might be a tell for others.

My old pipe spanner size was 1/2 inch, the new one 7/16th

[sujitroy]

I had a similar issue with the high pressure pipe going into the power steering rack. I got my file out on the outside of the flare. basically it was over tightened and flared out more that usual.

[Roy_S]

Well I have a nice new pipe fitted and a secondhand spare now.....