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MG MGA - Rear Brake Banjos

I have just rebuilt my rear brakes. All is working fine with the exception of a very slight leak at both banjo fittings. I installed new copper washers, but reused the bleed valves. Also installed new rear brake lines.

I have noticed after the fact that the banjos have a "ring" around one end but not the other. I have mine installed with the bleeder in the ring end. Barney's site has a photo showing just the opposite. http://mgaguru.com/mgtech/hydraulics/ht112.htm

Does it matter which way the banjo fittings are mounted?

John
jjb Backman

I don't know that it matters if the threads are the same each end. more to the point - banjo leak. You might want to flatten the banjo faces on some emery paper.
Art Pearse

The first question is, where does it leak? If you install it the right way around it should work with the later specification brake pipe. If you install it the wrong way around it might mate okay with the earlier specification pipe but not with the bleed nipple. Explanation to follow.

Confidential Service Memorandum MG/198, 3rd Jan 1957 notes the change from straight to L-shape rear banjo fitting commencing with (c)22741 (November 1956). This CSM does not mention any change of threads or change of connecting pipes.

The MGA 1500 Service Parts List does not show any change of part numbers at this production point (c)22741. This may seem curious, but it is possible that the new "L" shape part supersedes the earlier straight banjo fitting with no change of part number, as the parts are physically interchangeable using the same steel lines, same banjo bolt and washers, and same bleed nipple. The then new "L" shape parts would commence distribution under the same part number (with some expectation that old stock spares might be used up first).

From the 1500 SPL, the three-way fitting and the two steel lines from 3-way to banjo fittings and the banjo fittings all change part numbers at (c)27989 for disc wheels and (c)28540 for wire wheels. This carries through to end of production in 1962. There was never any change of part number for the bleed nipples.

The book "Original MGA" says the threads on the brake lines and banjo fittings were "standardized to UNF" at (c)27989 (March 1957) for disc wheels and (c)28540 (April 1957) for wire wheels. The threads would have been BSF type earlier.

For all of this to be true and not in conflict, there must be two different "L" shape banjo fittings. The first would carry one part number from beginning of production to (c)27989(dw) or (c)28540(ww) and change from straight to "L" shape with no change of part number at (c)27989. Then at the later noted production point the "L" shape banjo fitting would change to different threads for the pipe while keeping the original threads for the bleed nipple, and get the new part number because these parts are not physically interchangeable.

My best guess is that the ring around one end of the "L" shape banjo fitting designates the end containing UNF threads after the change of steel pipes. (Unified bolts and nuts are marked with a round dimple or small circle). This would imply that there may be an earlier "L" shape banjo fitting with no ring around the end having the earlier BSF type threads in both ends.

If anyone has an MGA 1500 between (c)22741 and (c)27989 this might be a good time to check the rear banjo fittings to see if they might be "L" shape with two bare ends and no ring.

My car is a little later that all of this, so it has the "L" shape banjo fittings with the ring on one end. To the best of my knowledge these are original factory issue parts that have been assembled in this way since new. I have disassembled and reassembled them a few times in the past 32 years, but always in the same orientation.

As to the difference in threads, UNF threads have 60-degree thread form, while BSF is the fine thread version of BSW (Whitworth) treads with 55-degree thread form. The later thread in the banjo fitting would be 3/8-24-UNF (24 threads per inch with 60-degree form), while the earlier one would be 3/8-BSF (20 threads per inch with 55-degree form).

It is tough to imagine trying to jam a male thread of either form into a female thread of the other form. The thread pitch alone is great enough difference to prevent complete assembly. What you would end up with is a fitting that goes tight with a wrench before bottoming out on the end as intended, so it should leak profusely around the pipe OD and through the threads.
Barney Gaylord

Art and Barney,

All is well now. I disassembled the banjos to make sure that they were UNF on both ends - they are. My A is a March '59 (64792) so I was well beyond the 27989 version. I heated up the copper washers to re-anneal them, I also touched the aluminum ends of the brake cyliners with 800 grit wet/dry. Cleaned off some clear-coat that was on the sealing surface of the banjo bolts, re-tighten everthing and bled the brakes. No leaks.

thx, John
jjb Backman

This thread was discussed between 28/06/2009 and 06/07/2009

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