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MG TD TF 1500 - Silicon (Dot 5) Leaks

I've rebuilt the brake system on the TF with new M/C and wheel cylinders. I'm using Dot 5 Silicon Brake fluid. My problem is that I can' t get the banjo joints on the front cylinders to stop seeping fluid.
I've done the following:
1. The first time I used new copper washers from Moss.
2. The second time I used new copper washers and "annealed" them.
3. I've tightened the banjo joints to the point I'm afraid to tighten them any more without stripping the threads.
4. I've made certain the surfaces of the banjo joints are flat.
The front banjo joints are the only areas I'm having a problem. Used Dot 5 in my 49 TC with no problems.
Any suggestions?
Thanks,
Mark Stolzenburg
Chesterfield, Missouri, USA
Mark Stolzenburg

Yeah, tighten them a tiny bit each day.
Dave Braun

Maybe you could try pouring some boiling water over the joint and then tightening it up again. I would be interested to know if you can get a torque wrench on to the bolt to see just how tight it is. Good luck with it.
Max Irvine

The sealing surfaces have to be nearly perfect. Especially check for any radial scratches, use magnification. Just because the cylinders are new does not mean the sealing face is flat and smooth. Try polishing the brass fittings and sealing face of the cylinders with increasingly fine grit sandpaper- start with 400 or so, then 600, and then 1500 or metal polish. Use a piece of thick glass or the edge of a Formica kitchen counter (when wife is not home of course), lay the sandpaper down and carefully sand while holding it perfectly flat. I ran across one leak that would not stop that was a crack in the banjo bolt, but likely not all 4 bad at once. George
George Butz

Mine had similar leaks. As I remember the brake pipe itself must be absolutely straight coming out of the banjo or they will leak. My latest technique if you want to give it a try:
1. Remove banjo from car. This is important!
2. Now screw banjo onto threaded connector at end of brake pipe making SURE pipe is straight!! Tighten only enough so pipe won't move for now. Easy to do with banjo off the car!
3. Bend brake pipe carefully until the new banjo/pipe "assembly" lines up perfectly with rear of brake cylinder. Insert nut and tighten banjo snug.
4. Now finish tightening brake pipe fitting to banjo.
5. Finish snugging up banjo.
6. You may or may not have to bleed at this point. I did not.
7. Cross your fingers and give it a try.
Hope this helps,
Ed
efh Haskell

mark, if your mating surfaces are true and defect free it should not take "near yield" torque on those banjo bolts. you do NOT want to strip threads or twist of a banjo bolt. it should not take that much torque. regards, tom
tom peterson

...should read "...twist OFF a banjo bolt." i should really fire my proof reader.
in addition to surfaces true and defect free the banjo bolt faces must be parallel. regards, tom
tom peterson

If the connecting faces are in poor condition they will never seal sugeest you try Doughty washers instead of copper washers.

Rgds Trevor Burnett
t burnett

What are " Doughty washers" and where does one obtain them?

Jim B.
JA Benjamin

Jim B.

Dowty Seals. A washer with a gasket on the ID.

http://www.jegs.com/p/Earls/Earls-Dowty-Seals/1712764/10002/-1

Bill
Bill Brown

Make sure the insert is VITON . The dowy seals are also available with a aluminum outher I considder them the best.Have no name for a US supplier but for the Dutch amongst us here : go to ERIKS and ask for a sample they mostly give you more then enough for a car for free.
Gerard Hengeveld

Well No more Dot 5 leaks!!! Thought I would provide a follow-up as to how the leaks were cured.
Basically I followed Dave Braun's advice and tightened each of the front banjo fittings each day. This cured 3 of 4 of the leaks. On the left rear banjo fitting I aligned it similar to Ed Haskell 's recommendation and then tightened every day until the leak stopped. This technique also stopped seepage from the bleed screws.
Initially I was afraid that if I tightened the fitting too much I would strip the threads but apparently the copper washers give just enough. I also used wood wedges to stop the metal brake lines that fit between the wheel cylinders from bending.
I want to thank everyone for the tips. They were all helpful.
Mark Stolzenburg
Chesterfield, Missouri, USA
Mark Stolzenburg

This thread was discussed between 02/06/2013 and 09/06/2013

MG TD TF 1500 index

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