Brake Line Question

I would try to tighten it a bit. I would be surprised if it doesn't need another 1/8th to 1/4 turn or so. DIN/ISO bubble flares need to be crushed a bit when they seat which is why they often don't work well when reused.

 

The S bit isn’t correctly aligned .So the flare isn’t evenly pressured by the nut internal flange .

Those front S hard lines are devils to line up .

For those curious… you have to undo this line to remove ( get a socket ) that bolt if you intend to remove / replace the caliper .

Obviously try nipping it up first .
But also try to reconfigure/ bend the S pipe .

I am a retired Orthodontist ( U.K. ) so “ wire bending “ if you like , getting things to align was part of my day job .
How ever these tested me ,

 

Agree. Doesn't look aligned.

 

The tube has to go straight in, with the flared end evenly seated at the bottom of the female hose fitting.... before the flare fitting engages the threads and starts in. Don't just tighten the fitting, slack it a few turns first and wiggle it to see if it you can get the tube in a bit more and straighter. It may help to slacken the hose/bracket connection a bit as well.
(But I must confess that I'm not seeing the misalignment but that's just me and maybe I should be looking harder).

Another possibility is that the flare or flare seat is damaged, or you got a bit of crud in there. I've had to flare and bend my own S-tubes (it's a lot easier with modern cunifer than the old steel stuff) a few times.

 

I agree it does not look aligned. As much as people struggle getting those in and out and as big a beating as they have taken over the 40 + years they have been taking that abuse and as few as I have had to replace in those 40+ years I really doubt perfect alignment was required or we would all be very well aware of that long before now. With a common open end I'd try tightening it a bit. Flare nut wrenches are only really needed if you intend to massively overtighten the fitting

If that does not fix it you have a bad line.

 

In the picture it looks like the end of the S-pipe is sitting low and off center in relation to the female (flare seat) fitting. The nut does not necessarily provide a centering function when tightening down the fitting. As you said, the fitting has to be seated (centered) before tightening down the nut. I would suggest that having tightened down the nut with the fitting off center, the OP may have caused some damage to the flare (which is softer than the seat) and should examine the flare to assess the degree of damage, if any.

 

Which if possible would have been a near daily occurrence since 1975 when that pipe started being used. Flare fittings are used precisely because exact alignment is not required. The flarenut to pipe clearance should be able to align the pipe to the degree required. If you want to make the case that the flarenut and pipe have a dimensional issue allowing a misalignment sufficient to allow a leak that is very possible but it it is aligned close enough for the flarenut to thread in,the fitting should not leak.

 

Send PMB a picture and ask them how to proceed. Unless you left it loose you need a new line.

 

I respect your many years of experience Brian. But there has to be some reasonable expectation of proper alignment before tightening down that fitting. If I am correct, a bubble flare is not particularly conical so I would think there is possibility of it being tightened down off center, perhaps pinching one side of the bubble flare between the nut and the rim of the female fitting, but not around the entire circumference of the flare. I believe I understand correctly that the softness of the tubing material allows for some squish of the bubble flare upon tightening to form a seal. But if that squish is uneven due to misalignment could it not result in insufficient sealing/leaking? As an aside, has there ever been any use of a compression fitting with a ferule (as used in the plumbing industry) for automotive brake applications?

 

The only alignment required is the flarenut.

Please, lets quit with the fantasy land diagnosis. That exact design has been in use since the 365s were in production in the late 60's. If a crooked pipe is all it took how many Ferraris have been built with that design?

Its a bad pipe. Either they made a bad flare or the pipe is a poor fit in the nut.

Move on.

 

What Antony said in post # .

When I did mine ( new callipers ) buttoned it all up bled it all through = nice rock hard peddle .
Great I thought.
Next day before going out in it I bent down to peek under from the front valance .A tiny wet patch apparent on the inside of the wheel rim and it just started to run down the inside of the tyre = shiny patch .Nothing on the garage floor yet !

So I traced it to the exact place in the pic ^ .

As said a bit of deft “ wire bending “ ( well the tube carefully ) i realigned it nipped it back up reusing the “ flare “ and it’s been fine ever since .

So if the car was @ a shop done that afternoon, then shipped back to the customer, then parked up etc it might be days before the issue was spotted .
Sure the flare might not be totally symmetrical, sure the inside of the flange rim on the nut might not be perfectly machined ……but it certainly helps if the pipe is as best square up aligned .Ok there’s a bit of wobble latitude Brian’s point , but it’s tiny .

So for best chance of success the S needs to be as best aligned as you can get it .