Just tried bleeding my front brakes and got good pressure. the problem is the union that goes into the caliper is weeping.
The caliper is a hi spec 4 pot.and the pipe was pre made with the calipers.could i use ptfe to help it seal?by wrapping it around the threads that go
into the caliper?
Chris
NO!
You need to find out why it is leaking. Assuming the seat and threads are good in the calliper then a re flare of the pipe is probably in order and a
new fitting for the end of the pipe if it is not in good order too.
I'm not sure what would happen to PTFE that is in contact with brake fluid but it could well degrade. Very bad practise and a "get you home
fix" only in my book!
YES 
PTFE doesn't degrade with brake fluid. I've got it on some of my joints and there's been no issues with them. There was even an article
in CKC a couple of months ago where John Dickens discussed this and the whole possibility of of a stray piece entering the caliper and the fact that
it will do no harm.
Ideally as Strontium says find out the cause but I'd say don't be afraid to use a bit of PTFE.
The concern over the degradation of the PTFE (and there is more than one type, which have you used?) is secondary to the concern over why it is
leaking in the first place! A correctly fitted union will not leak.It is NOT the threads of the union that seal but the compression of the soft metal
tube flare against the hard metal seat in the calliper. Now consider that if the leak is due to a small fracture in the pipe at the point at which it
flares. PTFE may well seal it up for a while but sooner or later the pipe will let go and probably suddenly. Now I appreciate the benefits of dual
circuit brakes and all that but would you like to lose all braking force ( or at best have totally unbalanced braking) to the front as you try an
emergency stop? The most likely time the pipe will let go according to the law of Murphy!
Get it checked and repaired properly by someone that knows what they are doing. Brakes and steering should be right, no exceptions to that! IMHO!
fluid must be leaking through the threads,the front joints ARE NOT compression joints .if the pipe is wound to the stop like a compression joint the
lower piston pushes out.
[Edited on 23/10/10 by chris666]
quote:
Originally posted by chris666
fluid must be leaking through the threads,the front joints ARE NOT compression joints .if the pipe is wound to the stop like a compression joint the lower piston pushes out.
[Edited on 23/10/10 by chris666]
Chris, you must have something wrong going on there. I've never seen a brake fitting that relied on the threads to seal unless it's a taper
thread. If it is a taper then PTFE is of with brake fluid but ideally should be avoided.
Do you have a picture of the pipe end and caliper.
Chris, where are you. If you are near Plymouth I'd be happy to have a look for you. If not then PLEASE get another engineer to take a look. You
can't afford for a fail here.
As Adithorp has just said, post a pic up at least!
Chris. Out of interest, you say the pipe was made with the caliper. Is there any way that you're placing the wrong end in the caliper?
just spoke to hi spec apparantly there should be a banjo union fitted to one end of the goodridge hose,also two copper washers.Will have to get hold
of some banjo fittings to go on my goodridge hoses.
thanks again.
life saving information.
p.s camera is not working.in the middle of buying a new one.
Chris
Chris
[Edited on 23/10/10 by chris666]
In over 43 years as a motor vehicle technician I have never had to use PTFE or any other sealant on a brake pipe fitting and IIRC it may be an MOT failure . When you think of the very high pressures generated in a braking system do you really want to rely on a piece of PTFE in an emergency stop? PTFE is fine in it's place but not on braking systems
The picture is clearing! Good job you posted up and sussed what is going on or that could have ended in tears!
The next question is what type of end is on the hose/pipe. When you called it a pipe is it in fact a flexible hose? Is it a taper and what thread is
it. I would take the hose to a brake specialist to make sure you get a banjo and bolt that is correct. A picture would tell a thousand words even if
taken with a phone.
Having said all that the calliper firm should be able to supply exactly what you need if the calliper came with the pipe from them in the first
place!
[Edited on 23/10/10 by Strontium Dog]
quote:
Originally posted by rusty nuts
In over 43 years as a motor vehicle technician I have never had to use PTFE or any other sealant on a brake pipe fitting and IIRC it may be an MOT failure . When you think of the very high pressures generated in a braking system do you really want to rely on a piece of PTFE in an emergency stop? PTFE is fine in it's place but not on braking systems
If he's only qualified to inspect OEM parts then I suspect that he is breaking the rules daily. Could he really fail it or just refuse to test?
If it were true then even a non OEM standard tyre or even winscreen wiper should be refused and if I were him I wouldn't want to put my neck on
the line. I suspect that there's a little more to the interpretation though.
Bajos on the way for the braided hoses.And banjo bolts with two sealing washers.will try to post pic to show finished article.
Chris
quote:
Originally posted by mistergrumpy
If he's only qualified to inspect OEM parts then I suspect that he is breaking the rules daily. Could he really fail it or just refuse to test?
If it were true then even a non OEM standard tyre or even winscreen wiper should be refused and if I were him I wouldn't want to put my neck on the line. I suspect that there's a little more to the interpretation though.
As to whether he would fail it or refuse to continue to test the result would be the same. No MOT and a bill to pay
anyway!
quote:
He was just commenting on the way the rules are going and how it is all getting a bit too much!