Leak at brake banjo unions

[frank drakman]

About 2 months ago I filled my new brake lines (actually the whole brake system is new) with silicone fluid but I am getting leaks at both brass brake unions at the rear brake cylinders. I am also getting a leak at the 2 way banjo union at the master cylinder. The banjo bolts are all new. The brake cylinders are new..all the surfaces seem flat..and I have replaced the copper washers several times. I have tightened the bolts up extremely tight yet I still get fluid leaking. The only parts that I have not replaced are the unions themselves (but their surfaces seem fine). Is this a common problem? Any suggestions? Would aluminum washers may work better than the copper ones? Has anyone tried that?

Thanks for any advice,

Rob Greaves

[m_e_jablonski]

Rob I had the same problem. I eventually sealed my leaks by annealling the copper washers before using them. It seems that commercial washers are often not fully annealed. Perhaps they anneal them before punching out thus they get work hardened after annealing. I also had to use more force on the bolts than I felt happy about. Haven't tried aluminium washers but they are softer and may be better. This was going to be my next option if I got any more leaks. One of my slave cylinder spigots was out of square and required truing in the lathe. If the leaks persist after using softer washers I'd check this. I also gave the spigots and banjos a light rub on fine emery (laid on a flat plate) to ensure there were no scratches (though your's are new so should be ok). At the wheel cylinders make sure that it's not residual fluid coming out of the bleed screw bore after bleeding, or running out of the thread. I had this problem too and thought I had leaks until I wrapped the bleed screws in rag for a week or so to mop up the remnant fluid. Part of the problem is that silicone brake fluid is like penetrating oil and finds the slightest leak. Thus remnant fluid easily runs out of the bleed screw thread and the central bleed opening, even though the screw is shut. I suspect that glycol based fluids evaporate, leaving a gummy residue which can eventually seal a slight leak. If the weep is small enough the evaporation rate would equal the flow rate and the leak would eventually seal. (Any chemists care to comment?) Or, in the case of the bleed screws the fluid would dry in the thread. Silicone fluid doesn't seem to evaporate. My leaks would only consist of a slight weep, becoming apparent after a week or more. I've noticed that my old brake components often had what looked like rust, which was hard to remove but turned out to be the gummy deposit from the glycol fluid. Hope this helps Mark Jablonski Melbourne Australia

--- In mg-tabc@y..., "Tammy Greaves" wrote: > About 2 months ago I filled my new brake lines (actually the whole brake system is new) with silicone fluid but I am getting leaks at both brass brake unions at the rear brake cylinders. I am also getting a leak at the 2 way banjo union at the master cylinder. The banjo bolts are all new. The brake cylinders are new..all the surfaces seem flat..and I have replaced the copper washers several times. I have tightened the bolts up extremely tight yet I still get fluid leaking. The only parts that I have not replaced are the unions themselves (but their surfaces seem fine). Is this a common problem? Any suggestions? Would aluminum washers may work better than the copper ones? Has anyone tried that? > > Thanks for any advice, > > Rob Greaves

[i.thomson@talk21.com]

Tammy, you must anneal the copper washers before use, and each time they are removed and replaced. Heat them to cherry red (put them in a gas flame) for a few minutes and then let them cool. I asked the same question in the Octagon bulletin many years ago and was told to quench them in water or oil to cool. My simple metallurgy expected this to harden with this treatment them but I was assured that this was not true for copper. I find, however, that just letting them cool naturally works just fine. I always flat them (and my finger ends) on fine wet and dry on a flat surface (the back of a vice) before use to avoid having to do the job twice. I had a recurring problem with the master cylinder union until I found that one of our esteemed MG specialists here in the UK, who had rebuilt the rolling chassis for me, had mated a TA master cylinder to a TC union (they have different tailpieces). I also would like to hear if people have used aluminium washers - what about telling us if any of you have. Ian Thomson -----------------

> About 2 months ago I filled my new brake lines (actually the whole brake system is new) with silicone fluid but I am getting leaks at both brass brake unions at the rear brake cylinders. I am also getting a leak at the 2 way banjo union at the master cylinder. The banjo bolts are all new. The brake cylinders are new..all the surfaces seem flat..and I have replaced the copper washers several times. I have tightened the bolts up extremely tight yet I still get fluid leaking. The only parts that I have not replaced are the unions themselves (but their surfaces seem fine). Is this a common problem? Any suggestions? Would aluminum washers may work better than the copper ones? Has anyone tried that? > >Thanks for any advice, > >Rob Greaves

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[Dean Jensen]

Tammy All the replies apply. I have also found that if after you have tried everything, and you still have a leak like this, in this case, take and put a film of silicon pipe dope, compound, on the surface of the washer. You want only a film, put some on your finger and wipe it on, just so you can see that there is something there, you do not want more than that, so the system is not contaminated. Regards Dean Illinois

----- Original Message ----- [b]From:[/b] t.greaves@hyperlinx.net [b]To:[/b] mg-tabc@yahoogroups.com [b]Sent:[/b] Tuesday, January 22, 2002 7:29 PM [b]Subject:[/b] [mg-tabc] Leak at brake banjo unions About 2 months ago I filled my new brake lines (actually the whole brake system is new) with silicone fluid but I am getting leaks at both brass brake unions at the rear brake cylinders. I am also getting a leak at the 2 way banjo union at the master cylinder. The banjo bolts are all new. The brake cylinders are new..all the surfaces seem flat..and I have replaced the copper washers several times. I have tightened the bolts up extremely tight yet I still get fluid leaking. The only parts that I have not replaced are the unions themselves (but their surfaces seem fine). Is this a common problem? Any suggestions? Would aluminum washers may work better than the copper ones? Has anyone tried that? Thanks for any advice, Rob Greaves Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

[joecurto@aol.com]

Ian we use the anneling technique here in my shop also but sometimes even that does not work and we have to use new, as for aluminium washers maybe there would be a corrosion problem against the steel bolts. Joe

[Roger Furneaux]

Re: [mg-tabc] Leak at brake banjo unions hi Rob - I also had the same problem with some copper washers, and also at the front with new bleed nipples in the old cylinders. the easy way to heat up the washers to anneal them is to cut up an old wire coat hanger, put all the washers on, and clamp the ends in a vice. with the washers on the bottom straight part (which is now at the top) heat with a DIY type gas flame. they heat up very quickly to cherry red, and only need a few seconds before cooling in the air. BTW I have always thought that if the machined surfaces of the cylinders and banjo had grooves from the machining, they would seal BETTER on the soft copper than smooth surfaces. ocTagonally Roger

[quote]About 2 months ago I filled my new brake lines (actually the whole brake system is new) with silicone fluid but I am getting leaks at both brass brake unions at the rear brake cylinders. I am also getting a leak at the 2 way banjo union at the master cylinder. The banjo bolts are all new. The brake cylinders are new..all the surfaces seem flat..and I have replaced the copper washers several times. I have tightened the bolts up extremely tight yet I still get fluid leaking. The only parts that I have not replaced are the unions themselves (but their surfaces seem fine). Is this a common problem? Any suggestions? Would aluminum washers may work better than the copper ones? Has anyone tried that? Thanks for any advice,

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