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MG Midget and Sprite Technical - Spongy Brakes that Fixed Themselves

Last weekend when I was out in the midget, the brakes were really spongy (I didn't remember them being so bad last time I drove it) and would take a couple of pumps to get them working every time I wanted to slow down. It was a bit scary! :-s

I tightened up the rear drums, still the same. Then suddenly, for no apparent reason, they started working OK and I had a firm pedal.

Something odd is going on but I can't figure out what. Maybe a M/C problem? (It's a new plastic type). Any ideas?

Thanks folks.

Malcolm.
Malcolm Le Chevalier

Quick thoughts.

Could be air that's moved in/around or out of system.

What about damp/wet/something else on your brakes that dried out with use(?).

Any difference at all in fluid level in reservoir?
Nigel Atkins

Front wheel bearings ?
GuyW

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Let me guess, you said no to an opportunity for some gay sex didn't you.... CHA CHING, reward from god

Haha

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Any new parts fitted recently/fairly recently(?).
Nigel Atkins

I've had it before when the pedal operated at different heights occasionally, it ended up being worn pedal pivot and clevis pins. The holes and bushes were also worn in the pedals. I guess the pins were turning and depending on the wear was giving different positions. It also affected the clutch pedal as well. A full rebuild of pins, bushes and weld/red rill pedals and the difference was amazing.
Didn't really give a feeling of spongyness but occasionally the brake worked at different heights which was a bit worrying at times! Might be worth looking at anyway.
John Payne

Nothing changed since it was last working.

Just went out this evening to see how the pedal felt/if it had changed and *boomf* flat to the floor with no resistance at all. It comes back with a bit of pumping, but not properly firm.

Fluid level hasn't dropped that I can tell, so duff M/C I suppose?

More quality repro parts. Lucky I kept my tin one, nobody wanted it when I put it on eBay! :-D

Malc.
Malcolm Le Chevalier

That definitely sounds like the master cyl, I bet it makes you glad it only went to the floor in the garage!

They do the metal ones new again now but they are a bit pricey.
John Payne

Go with a new M/C. I had a similar happening with my 79-B. The seal to the vacuum booster failed and sucked the brake fluid through to the intake manifold and it was burned along with the fuel. Scary when you hit the brake pedal and straight to the floor.

So yes, new M/C

Cheers,
Gary
79 MGB
gary hansen

Are the seal/repair kits available any good? Or more junk rubber?

I will clean and rebuild my old M/C and replace.

The new one has lasted 3 years tops. Useless.

Malc.
Malcolm Le Chevalier

This is a classic case of where brake pipe clamps, help with a diagnosis, saves a lot of time, and you can prove the fault,
Andy Tilney

I would be a bit weary about rebuilding a M/C. Over the years the bore gets pitted and may cause another premature failure. Go with a new one. Be sure the new unit is a fresh cast body and of course, new internals.

Don't screw around with safety parts.

Cheers,

Gary
79 MGB
gary hansen

Malcolm

Try to see if you can get a genuine (AP Caparo) master cylinder - ask Powertrack Brakes Ltd.

(if not, try Past Parts or Coastings Ltd, and perhaps Leacy Classics to see if they can supply a genuine part).

Thanks
Mike
M Wood

Now is the perfect time to toss in the towel and do a tri cylinder master set up, perfect for a winter time project

Once you do it, you will have no regrets ... I used a tilton kit... peddles master's the worksx there are other brands and many have had success using the original peddle assembly.

Look in the archives under Bill young as one of his last projects before he passed on... maybe 3 years ago +/- a year

And others have done it as well, but it's a great set up and worth more then the cost just in relibility

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This thread was discussed between 27/11/2017 and 29/11/2017

MG Midget and Sprite Technical index

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