MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Rear brake cylinder.

I have replaced the offside rear brake cylinder and have been having trouble getting a seal. I bought new copper washers that go either side of the banjo fitting.

I first did it up good and tight and then a lot more as it still visibly leaked when the brake was applied. Then I took it all apart again and gently filed all the mating surfaces - both sides of the washers and banjo and the banjo bolt, and made sure that there were no burrs on the surface of the slave cylinder and that the rubber boot wasn't getting in the way.

After that I gave everything a wipe to remove dust and grit.

I eventually got a good pedal pressure but only after doing it up really tight. I didn't have nearly as much trouble last time I did this job.

When doing up the banjo bolt, the it was difficult to stop the banjo from rotating and twisting the brake pipe connection.

Is this going to be alright? Is there anything else that I could have done?
Dan Smithers

I always anneal the washers before doing this and I also (get ready for criticism) put PTFE tape around the washers when fitting to help the seal
Bob Turbo Midget England

The new copper washers should have been fine as long as the banjo, etc were clean and undamaged. Having tightened it all once you should have annealed the washers as they will have been squashed which work-hardens the copper. To anneal them, wait till the wife's out the way and with the washers hanging on a bit of iron wire heat them to red heat over the gas stove and then quench in cold water. Clean up with a wire brush and they should be ready to go again. I wouldn't use a file as the surfaces could then leak.
Pete
P N Tipping

I didn't say, but I was using my fine-toothed flat needle file and the surfaces were a lot smoother afterwards than before.
Dan Smithers

Pete,

To anneal the copper washers they should be heated to red heat and then allowed to cool in the air.
Quenching them in water after heating will harden them.

Mick
M F Anderson

Dan said "...the surfaces were a lot smoother afterwards than before." Unless it was annealed and perfectly smooth, you really don't stand much of a chance.

I don't use a file either. Files leave a lot of micro grooves and undulations. I place a piece of 220 wet/dry sandpaper on a piece of glass with few drops of water between them. Then I wet-sand in a figure-8 and circular motions until I get a consistant looking finish (all groves and blemishes are removed). Then do the other side of the washer. When done, I check for flatness using a micrometer in 4 places around the outer edge of the washer. I generally try for less than 1/2 thou difference. Of couse this cannot be done on the cylinder or banjo.
Chuck Schaefer

Mick,
You need to heat copper red hot and quench it in cold water to anneal it. It's the opposite of annealing steel. It sounds wrong, but that is the way it is done.
Ed Bell

Hi Ed,

As I have always annealed copper by allowing it to cool in air I went back to my metallurgy textbooks.
It appears that copper, brass and silver can be annealed by either cooling in air or quenching in water.
Ferrous metals must be cooled in air.
I should have remembered that but over time we rely on our habits.
Thanks for the reminder.

Mick
M F Anderson

I'll take the joints apart again and anneal the washers, check for flatness and smoothness. Then reassemble.

I considered doing this in the first place but decided to buy new washers and save the time and effort.

I do remember when I studied a bit of metallurgy that copper and brass can't be hardened by heat treatment.
Dan Smithers

This thread was discussed between 26/03/2012 and 30/03/2012

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.