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MG TD TF 1500 - New brake pipe testing experiment shows leaks

Oh no, they say in unison! Not this topic again!! But I'm trying an experiment not seen in archives & would appreciate your thoughts.

I've installed 1 new Moss bridge brake pipe that connects the 2 front brake cylinders. No brake fluid added yet! Before I move on I decided I should check for leaks somehow. So I set my air compressor very low (10 psi), squirted some water on the various connections, and fed air through the brake hose. Of course, I get bubbles at all 4 connections (pipes & banjo's)! I've read to never overtighten the new pipes lest you ruin them. I've tightened as much as I had nerve to do, but still get bubbles. I removed the pipe to inspect and flared ends look indentical to other new unused pipes in the set and old pipes as well.

Should I continue to tighten pipes until bubbles subside or try something else? All opinions are welcome!

Gracias,
Ed
efh Haskell

Fyi, I just ordered a can of Gasoila in anticipation, but I shouldn't have to use this stuff. My old pipes never leaked and had no such stuff on them I could see.
efh Haskell

Personally I would tighten them nice and snug. Sometimes the flare needs to conform a little to a less than perfect opposite half.
Steve Simmons

Ed, over-torquing is a recipe to ordering more parts. Let it sit for a while then recheck the torque. Of course cleanliness is the utmost in assembly. Flat smooth annealed copper washers are a must. Go easy on thread sealant applications as excess can be worked into the cylinders (none on flat washers). As always a couple hours at night spent reading the archives goes a long way. Not comfortable about using pressurized air as it's not designed for it.
Have fun, Mike.
Mike Hart (52 TD 16378)

Has anyone tried Teflon tape?

Gord Clark
Rockburn, Qué.
Gordon A Clark

Sealer, including teflon tape on the threads is useless - the sealing surface is the flair on a similar reverse flair on the inside of the fitting. Cheers - Dave
David DuBois

i'm chiming in with same info as the rest of the posters...DO NOT over torque. clean, clean, clean. goop on the fittings, in my experience, is just another source of contamination. as you route the lines take an extra moment or two to make sure the line is entering the fitting and B nut straight on. the B nut should spin down snug by hand, then torque. regards, tom
tom peterson

Ed,
Hopefully you'll find, even if air escapes, brake fluid won't. Viscosity makes a huge difference. If you really want to check for microscopic leaks, try helium.

I do encounter leaky brand new brake lines too frequently. It pains me to have to remove it and reflare the factory ends to make them seal.

Since you don't have brake fluid in it yet, anneal your copper banjo washers dead soft. Hang them on a wire, and heat them cherry red for about a half minute. If you dunk them in water while red hot, the oxide will flake off leaving them a nice & pretty copper color. A stove, propane or prestolite torch will do. An oxyacetylene torch can melt the washers if one is not careful.

Sometimes I heat the flared joints red hot to anneal them, but no quench. Conforms better to the mating surface.

Very frequently I anneal the tube end before flaring- makes it easier to flare, seal better, less likely to crack while flaring, and less likely to fracture at the base of the flare years down the road. I repair flared tubing all the time.

As a last resort, there are preformed copper inserts that sandwich into the flared connection for better integrity.

By the way, I don't like Gasoila. Goes on slick, but sets hard. Not forgiving if you have to take it apart or adjust the joint later on. Won't help on the flared joints.

Have fun Ed!

Jim
Jim Northrup

If the banjos are leaking, did you replace the copper washers? The mating faces of the banjo, bolt and wheel cylinders must be really clean and scratch free. The set of Moss pipes I got a couple years ago had beautiful brass fittings, don't see how they would leak. . Likely crud in the banjo keeing the flare from seating. I agreee goop or tape totally useless w/ brak system pressure.
George Butz

Being a plumber for 10 years my experience with compression fittings was this. 1/4 turn with a wrench, and then pressurize system. Spray joints with Windex Fantastic... and then slowly tighten until bubbles disappear. With water compression fittings, I do it the same way but until drips stop. I wipe with a clean dry paper towel which helps me see if there are any more leaks.

I agree that with a thicker more viscous fluid like brake fluid the rules might be different but some of this insight can apply.

As stated above - NEVER OVER TIGHTEN. You'll just be back to buying new parts as the mated faces will never un-deform.
vping

This thread was discussed between 22/10/2010 and 23/10/2010

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