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MG MGA - leak - brake fluid ?

Hello all experts,

I installed a new master cylinder together with new copper brake pipes etc. the whole brake system is new as to say. Than the important moment is there to check everything. A (extremely small) leak occurs on the exit of the master cylinder. Could the use of silicone brake fluid be the reason of the leak ? As far as I can say (and trust my mechanic skills) everything was put together with much care, hence my unbelievable surprise when I noticed the leak.
Any advice from all of you ?
Many thanks in advance,
Kind regards,
Guido
gva guido

Is the leak on the front side of the master cylinder (where the pushrods are located) or on the back side of the master cylinder (where the brake line attaches)?

If it is on the pushrod side, then fluid is leaking past the piston seal which will require a recheck of the seal and bore of the master cylinder. Getting the piston seal on correctly can be a chore. It's possible for it to be incorrectly installed but still "look right." See
http://www.mgaguru.com/guest/mgashop/mcrebuild.htm

for a visual tour of rebuilding the master cylinder.

If it is at the brake line connection, then it may be as simple as retightening the brake line connection.

I personally do not have any experience with silcone brake fluid, but I know that there has been a lot of discussion on this board over the years about silicone fluid so check the archives.

Good luck and keep the board posted on your progress.

Don Carlberg
Don Carlberg

No silicon does not cause leaks.
Were the brake lines Bubble type?
"Normal" double flare brake lines won't seal in this system. This picture shows the master clyinder end of both the clutch and brake lines.


R J Brown

In fact the important leak is at the clutchline, where we need the 3 copper rings to fix the whole. I warmed up these rings (as I was told to do) and tighted all the parts together. The leak comes out when I push the clutchpedal. It is just like a little cloud that appears, the leak is that little.
That is why I doubted about the silicone fluid which could be thinner than the classic brake fluids.
We will try again tomorrow with a new set of rings, hope to have more luck...
Regards,
Guido
gva guido

"I warmed up these rings (as I was told to do) and tighted all the parts together."

I am curious as to what you mean by this. How hot did you warm them and were they hot when you assembled them. If they were cool when you assembled them how did you cool them?

Did you use new copper washers? You should only have to heat previously used copper washers. This is called annealing. Copper work hardens in use. Copper needs to be soft so that it will crush and seal properly. To do this you heat them cherry red and let them slowly air cool to room temperature. If you cool them too fast they will harden. Again, if you used new copper washers you should not have to heat them.
Jeff Schultz

Where I worked, we made electrodes for induction heat treating out of copper square tubes. We annealed it by heating it to cherry red and quenching with cold water. It would come out dead soft and very workable.
Ed Bell

Guido

The lesson from Jeff about copper is most interesting and a information I have now stored in my brain.

Many of us use silcon fluid with no problems. I have used it for 12 years, others for up to 26 years. One of the advantages is that when the system does leak, as yours is doing, there is no risk of damage to the paintwork.

Steve
Steve Gyles

I never reuse a copper washer without 1st sanding down the surface on a flat plate to remove the indentations made by previous installations. Then anneal it. Once this is done, no problems.
C Schaefer

Guido, Mine also leaked after re-build. The trick With these hydrolic lines, much like plumbing fittings, is to continue to torque down the nut a little at at time while checking it. I would turn it about an eight inch at a time. It will eventually stop.
WMR Bill

it is like Ed wrote, I had many years professional experience with used and new copper washers, heat them cherry red, drop in water will make them perfect soft and you can use them as long as they stand the mechanical strain. If overheated they will deform and are scrap.

Siggi
Siggi

I agree with Siggi and Ed - we used large copper pipe gaskets in the steelworks - always heated them up cherry red and then dropped in water to anneal - now steel is different matter...
Mike
Mike Ellsmore (1)

This thread was discussed between 21/11/2008 and 24/11/2008

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