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Rear wheel cylinders

Posted: Fri Feb 13, 2015 6:19 pm
by sahtuning2000
I have just renewed the rear cylinders but i,am having trouble getting the NSR one fluid tight,i used a new cyliner but the original pipe as this undone fine from the cylinder,but when i replaced it and bleed the system its developed a leak from what looks like the thread,so i removed the pipe from the cylinder to the brake hose,had a new pipe made with new unions,refitted it and it STILL leaks,but not as much,i,am now thinking it may have a casting/thread issue on the pipe hole,anyone else had this issue?
I,ve bought another cylinder from another supplier and was going to fit that.

Re: Rear wheel cylinders

Posted: Fri Feb 13, 2015 6:31 pm
by ljd
just done them on my pi estate also i did pipes as well havnt had any probs, try bleed nipple in threads before you put pipe back might sort threads good luck

Re: Rear wheel cylinders

Posted: Fri Feb 13, 2015 6:36 pm
by sahtuning2000
I spoke to Chris and he did sort of mention a possible machine era as they are cheap and not Lockhead,i will go with the other one i have tommorrow and take it from there i think,i can,t understand leaking from 2 different pipes/unions.

Re: Rear wheel cylinders

Posted: Mon Feb 16, 2015 8:38 am
by Clifford Pope
I had the same problem. I found that the slightly projecting unthreaded part of the brake union was a tiny bit wider than the hole at the bottom of the threads, so it didn't quite tighten on the pipe itself.
I chamfered off the leading edge of the union a little to let it fully enter the hole in the cylinder.

Rear wheel cylinders

Posted: Tue Feb 17, 2015 6:05 pm
by Polly
Clifford Pope wrote:I had the same problem. I found that the slightly projecting unthreaded part of the brake union was a tiny bit wider than the hole at the bottom of the threads, so it didn't quite tighten on the pipe itself.
I chamfered off the leading edge of the union a little to let it fully enter the hole in the cylinder.
Perhaps I'm teaching grandma to suck eggs, but speaking as a plumber, the threaded portion plays no part in forming the leak proof seal, that is actually the function of the flared end, and the function of the thread is purely to hold the joint in place.
So with that in mind, any fault with the thread would have to leave a loose joint. I appreciate it might be difficult to detect a slightly loose joint with it in position, but after checking for looseness I would open the connection and look at the flared end carefully. You should look for some evidence that it had been compressed by the nut, and that there are no splits on the flare.


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Re: Rear wheel cylinders

Posted: Wed Feb 18, 2015 10:29 am
by Clifford Pope
Yes, that's exactly what I found. The union tightened up hard, but did not squeeze the flared end quite enough to contain fluid under pressure.
There was no play as such - the only way to detect it was to connect the cylinder onto the pipe free from the back-plate and I found it would rotate on the pipe.