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MG MGA - Rear brake leak

I have just replaced one of my rear wheel brake cylinders, reusing the old banjo but replacing the 2 copper washers either side of the banjo unit. After bleeding I noticed brake fluid on the floor, so I tightened everything up (not that anything was loose) and tried again. Same result. On closer inspection I found that the fluid is escaping under pressure from the banjo bolt, so presumably one or both of the new copper washers?? I am now wondering if I need to replace the banjo, banjo bolt and washers (again) as it's as tight as it will go but still leaking.
Any thoughts or suggestions please?
Thanks
Robert Sinclair

Robert,
you would be best advised to replace the copper washers.
Copper hardens when compressed and the old ones are probably now too hard to make a good seal. New softer copper washers should squash to make a good seal

In theory, you can anneal copper to soften it again but this probably won't work because the washers will have already been squashed to be thinner than a new washer will be. Not worth the effort or the risk of it not working.

New washers are listed as only 68p from Moss (+VAT), so it has to be worth a try.

Cheers
Colyn
Colyn Firth

I did replace both washers, Colin, so find it hard to believe that they could be the culprits!
Robert Sinclair

Most modern made parts are to be suspected when fitted, assuming the copper washers are the correct size, or that the leak isn't from the flexi-hose being disturbed - but this from another thread. -

richard b, Zumerset, United Kingdom
"The process of stamping out the copper washers can work harden them.

Anneal by bringing to cherry red and dunk straight into water - i.e. quench - or slow cool - no difference for copper unlike some steels.

Maybe worth just rubbing the washers on a flat file to check they don't have raised edges from the punching."
Nigel Atkins

In that case Richard, it may be time for some new brake hoses as well as another set of copper washers.

Moss Europe parts

"HOSE, rear brake
1500cc, 1600cc & MkII GBH104"
approx £13 + Vat

Cheers
Colyn
Colyn Firth

Yes, I think you're right. Having had issues with replacement brake cylinders in the past, when the new one was fractionally larger than the one it was replacing, I'm also wondering if there might be an issue with the new cylinder and the old banjo bolt. Could it be that the old bolt is too long for the new cylinder and therefore won't tighten fully?
Robert Sinclair

This thread was discussed between 25/07/2022 and 26/07/2022

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