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Brake Unions, How Tight?


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#1 Deathrow

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Posted 30 April 2018 - 01:54 PM

I've searched the forum to see if I could find a thread on this but there doesn't seem to be one. Apologies if I'm just not searching with the correct terms but I think I've been fairly thorough.

 

I've just finished bending up the last of the pipes for the Elliot's brake system and they're all now installed. I'm going to go round and do a final check before marking each joint with Tipp-Ex so I know I don't need to fiddle with it any further.

 

How tight should brake unions be? I want them to seal but I'd also like to avoid over-tightening them so they're still serviceable in the future. Due to the nature of a brake union, traditional socket torque wrenches aren't of any use.

Is there a rule of thumb for how to tighten unions? How do you do yours?



#2 GraemeC

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Posted 30 April 2018 - 02:01 PM

Nipped up, then checked for leaks and then nipped up further if needed.  ;-)

They need to be reasonably tight as you're effectively deforming the end of the flare to create the seal. Light ipe of copper slip on the thread section should make them easy enough to undo later.

 

Treat yourself to a paint pen - much better than tippex.



#3 johnR

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Posted 30 April 2018 - 02:02 PM

I'm guessing it depends to some extent on whether your pipes are copper or Kunifer - the latter is harder I believe so presumably would need a little more effort to get the same tightness.

Probably the worst thing you can do is overtighten because this can lead to a fracture behind the union.



#4 Deathrow

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Posted 30 April 2018 - 02:34 PM

Graeme I swear you must have a notification set up for whenever I post a thread  :D. It's not a bad thing though!

John they've all just been replaced with Automec pipes from MiniSpares which I believe is all kunifer piping.

When we're saying nipped up, I'm thinking gently tighten until resistance is felt and then 1/8th of a turn? Sorry to be so pedantic about it, unfortunately my OCD doesn't let up unless I know exactly what I'm doing!

I might have to get myself a paint pen, the Tipp-Ex is a bit fiddly when you're shuffling about underneath stuff. Better than not marking them though :-).

Does the same procedure apply for the banjo bolts on the driver side front brake hose and the clutch slave cylinder? I feel there's less danger of over tightening here but I guess you're only really crushing some copper washers.



#5 GraemeC

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Posted 30 April 2018 - 02:39 PM

1/8 - 1/4 turn once it feels like it is squahing the flare would be about OK I think.

Similar for banjos.  The think to watch there is that the banjo itself stays in the alignment you want it to - a little bit of lube (even just some brake fluid) on the washers helps here.



#6 Steve8274

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Posted 30 April 2018 - 02:59 PM

Ive just redone all mine with kunifer pipe. Wish I had used copper to be honest. I have a few joints that have a slight drip after few days. Very annoying. I initially tightened them all up till I could feel resistance then did another 1/4 to 1/2 turn. Seems to have worked on most joints apart from 3. I have since gone round and tightened these bit more but still few drips. They feel rather tight now so want to avoid tightening further.

Edited by Steve8274, 30 April 2018 - 02:59 PM.


#7 Spider

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Posted 30 April 2018 - 06:17 PM

Nipped up, then checked for leaks and then nipped up further if needed.  ;-)

They need to be reasonably tight as you're effectively deforming the end of the flare to create the seal. Light ipe of copper slip on the thread section should make them easy enough to undo later.

 

Treat yourself to a paint pen - much better than tippex.

 

This is about what I do too, though I do generally find, with new flares some do need that extra nip the first time they are done up.

 

I will though express some concern about using any marker or paint types pens or the like for fear of introducing a contaminate or even a paint flake.

 

If I've re-piped a car, I bleed it through first with metho to check for leaks and also to flush the system, the metho is 100% compatible with all brake components and won't damage paintwork it there is a leak, then once happy with that, drain off, flush and fill with Brake fluid.



#8 Stu1961

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Posted 30 April 2018 - 06:39 PM

The main thing is not to overtighten them, you can always nip them up a bit more if you get the odd drip. The most critical bit in my view is removing all traces of swarf from the freshly deburred tube/pipe end and forming tool, this will ensure the flare is formed correctly with no deformity's. Lubricating the tube will also help as well during the flare forming stage and subsequent tightening. As far as copper washers are concerned everyone I fit at work gets annealed before use, they rarely leak fluids or compressed air/gas.   



#9 Deathrow

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Posted 30 April 2018 - 08:40 PM

Thanks for the replies everyone.

 

Graeme, I'll go 1/8th and then check everything once there is fluid in the system.

 

Steve, I really hope I don't encounter the same issues you've had. It'd be an absolute headache at this point and I really don't fancy removing all the pipework again.

 

Moke, that's a fair comment. I've been really careful to ensure that the pipes and the fittings are clean and clear before fitting them to the car. Each pipe has had brake cleaner blasted through it and across the threads of the fittings to ensure it's all clean. I've even given ample time to make sure it's all evaporated before fitting.

What do you mean when you refer to metho? It makes me think of methylated spirits here in the UK but I fear that might not be what you mean. When I fill the system I might go in with the intention of filling it, only to entirely replace the fluid after it's been in a few weeks with the hope that it'll give the system an initial clean. Though everything in the system is brand new or has been cleaned very carefully (banjo bolt, front brake union (on top of driver side brake hose) and the rear 3 way union). I do wonder what they lubricate new master cylinders and brake valves with though, I can only hope it's brake seal safe whatever it is.

Stu, am I right In thinking that annealing copper is actually the opposite to annealing steel in that it must be heated and quenched?



#10 nicklouse

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Posted 30 April 2018 - 08:45 PM

yes meths. the purple stuff.



#11 gazza82

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Posted 01 May 2018 - 07:21 AM

Read yesterday that imperial joints need a copper washer and do not touch the bottom of the fitting, so wouldn't cause further squashing. Metric however do screw right down and use this to seal and don't use washers leaving a gap.

#12 Spider

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Posted 01 May 2018 - 07:58 AM

What do you mean when you refer to metho? It makes me think of methylated spirits here in the UK but I fear that might not be what you mean.

 

Yeap, that's the stuff - Methylated Spirits.

 

It is harmless to Automotive Brake parts and is referred to in one of the factory workshop manuals to use as a cleaner of brake parts. It's what I've been using since the year Dot. Brake Fluid too can be used for this, however, I can't stand that stuff on my hands.

 

And of course, there is Brake Cleaner too, but dearer (considerably) than Metho.



#13 Ethel

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Posted 01 May 2018 - 09:03 AM

Gazza, what you've read about washers applies to hoses only, metric ones seal like pipe flares so don't try to tighten to the flats. Easiest to just look in the hole to see if there's a seat matching the male end. Also test assemble without washers to check the fitting will screw in fully.

Anneal copper by heating until you see a Reddy colour change and let it air cool. You can use an electric hob.

The purple is a dye to discourage you from drinking meths, it's just ethanol. You get a crystalline residue around the caps of meths containers, so I prefer the pure stuff, tastes better too!

Hope the disclaimer that's a joke is unnecessary and I doubt residue is an issue if you don't leave it sitting in your lines long enough to evaporate.

#14 Stu1961

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Posted 01 May 2018 - 05:08 PM

Thanks for the replies everyone.

 

Graeme, I'll go 1/8th and then check everything once there is fluid in the system.

 

Steve, I really hope I don't encounter the same issues you've had. It'd be an absolute headache at this point and I really don't fancy removing all the pipework again.

 

Moke, that's a fair comment. I've been really careful to ensure that the pipes and the fittings are clean and clear before fitting them to the car. Each pipe has had brake cleaner blasted through it and across the threads of the fittings to ensure it's all clean. I've even given ample time to make sure it's all evaporated before fitting.

What do you mean when you refer to metho? It makes me think of methylated spirits here in the UK but I fear that might not be what you mean. When I fill the system I might go in with the intention of filling it, only to entirely replace the fluid after it's been in a few weeks with the hope that it'll give the system an initial clean. Though everything in the system is brand new or has been cleaned very carefully (banjo bolt, front brake union (on top of driver side brake hose) and the rear 3 way union). I do wonder what they lubricate new master cylinders and brake valves with though, I can only hope it's brake seal safe whatever it is.

Stu, am I right In thinking that annealing copper is actually the opposite to annealing steel in that it must be heated and quenched?

Sorry for the late reply Adam, heating copper then allowing it to cool naturally will soften it, heating it then quenching it will soften it even more  though is not essential, however if you quench steel in oil or water it will harden in most cases.        






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