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MG MGB Technical - MGB flexi brake hose to caliper leaks

Hello all,

So about a month ago, I did a long overdue service on the BGT. Everything was new or rebuilt on the brake system except the metal lines (master cylinder, flexi hoses, calipers, rotors, drums, wheel cylinders, pads, shoes, hardware.....even handbrake cable!). Also did the clutch hydraulics and rear axle seals while I was at it all.

Anyway, when screwing the front flexible brake hoses into the calipers, I could not find a wrench that fit perfectly, making me feel like they were not tight enough. 9/16 and 5/8 were just a bit big or small, and metrics did not work either.

So, needless to say, I have a leak on both calipers where the flexi hoses screw in.

It could be junk aftermarket hoses maybe, or not quite perfect copper washers (they did not come with the hoses, so I had to run into town and get some that I thought fit the best....but not specific to MGB), or just not tight enough.


I am going to get new hoses and washers, but before I do so, has anyone had this issue? Or does anyone know what supplier has a brake hose that has an end that I can fit a standard wrench to in order to tighten?


Never had leak issues before, and I have redone the brakes on my Imp, Robin, and early B roadster multiple times!


Thanks,
Julian
Julian Dufour

I had a similar issue last year. I seem to recall the spanner size was 19/32 inch. But I would have to check this. The hoses have to be tightened and then a bit more. I think I extended my spanner for more torque. Of course, you will round off the unions trying to do it with the wrong size spanner. They need to be tight. Any sign of a small seepage of fluid is clearly unacceptable. But you will know all of this.
C Harvey

Thanks.....glad to see I am not alone in this! If anyone knows that this is the correct size, please chime in. Perhaps I will end up with the same issue with new brake hoses, so maybe instead I just need to invest in an odd sized wrench!!!

Julian
Julian Dufour

The hex on these is a Whitworth spanner size.
Colin Parkinson

Yep. It surprises me that 15mm didn't fit
Also, when you tighten them up ,loosen them off and retighten a couple of times to work the copper washer into a good seated position
It's possible the washers aren't quite as soft as they should be and a bit of a loose/tight session will help them seat in
or
you could anneal the washers if you have something to heat them up with
willy
William Revit

The correct size spanner for the flexible brake pipe is 19/32" A/F, And the sealing washers are not just any old copper washer you need to get the correct ones from a brake component supplier,
Andy Tilney

The problem I've had with hydraulic fittings on the MGB is that replacements are rarely the same size hex as the ones I took off, making spanner choice a lottery. With oil cooler hoses I've had to resort to a small 'copper' coin wedged in the jaws to pad it out before now. You do need a correctly-fitting spanner (or spanner plus coin ...) to get enough torque on them.
paulh4

Spanner size for these hoses is 5/16 Whitworth. Historically hydraulic fittings were always Whitworth hex.
I have no idea why they (Moss?) insist on still using these obsolete spanners sizes, as aftermarket hoses for classic cars, back in the day, went on to AF spanner sizes, and then Metric.

Ebay good source of Whitworth spanners.

Colin
Colin Parkinson

Thanks all--

Found a Whitworth spanner set for not too much on ebay, so will purchase it. The copper washers I used were from an automotive store, so hopefully they are adequate....if not, will get some more.

Would rather buy some more tools than another set of new hoses with the same spanner size requirement....and hence the same problem!

Julian
Julian Dufour

This thread was discussed between 07/04/2019 and 09/04/2019

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