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MG MGB Technical - I can't get a stiff

brake pedal. At least I got your attention. Is it possible to get air into the brake lines without a leak. I have bled my brakes a couple of times and i cannot get a good pedal. it is always a little spongy.
I also have a problem at stops where while holding the pedal down, it suddenly goes to the floor, like something gave out. I have not lost any fluid however. It is still full. One last symptom. I did a copmplete bleed l;ast year at this time, now inside the reservoir it is very dirty. Where could the dirt come from.

Thanks

Ken
70 B
Ken Harris

This sounds like master cylinder seals breaking up .
S Best

Your master cylinder is failing...the muck is a broken up seal and fluid is leaking past it hence the foot to the floor syndrome...you either need a master cylinder repair kit or a new cylinder complete if the old one is scored inside.
You kinda need to do this now too!
Good luck
P J KELLY

A little Viagra put into solution with Catrol LMX and added to the reservoir will harden those brakes right up.

* only kidding....better living through chemistry, I always say! *

rick
your resident pharmacist
rick ingram

Mine went three months ago: pedal hit floor at 40mph approaching roundabout. Quick change into second and handbrake saved the car (and me). Police car following me didn't even notice.

I should have known it was coming: slightly sloppy brakes the day before. Foot under the pedal to lift it then gave a semblance of brakes.

New seals for the master cylinder sorted it; luckily the MC was not in bad condition. Oddly, the seals looked OK too...
shane rj

I was afraid you would all say that. But if the seals were going, would there nbot be a leak somewhere? The reservoir is staying at the same level as when i filled it last year.
Ken Harris

Leak?....often no...the fluid simply goes past the leaky seal...no pressure...no brakes!
P J KELLY

Ken, for some reason it's difficult to replace the seals in the dual master cylinder. I tried several times on my 74 and eventually gave up and bought a new MC. Even then it's best to try and bleed the new one on the bench prior to installing it. Good Luck.

Andy
Andy Preston

Something I've recently come across while helping my neighbour with his Harley is that sometimes the bleed nipple won't seat properly any more (Overtightening, etc). This causes sponginess like an old master cylinder. After resurfacing the nipple seat with a drill and changing the nipple, the brake worked as it should again. This was of course discovered after the rest of the system had been rebuilt. We could tell there was a problem because air bubbles in the clear tube we were using to bleed the system were moving when the lever was pulled and the bleed screw was tight.

Anthony.
Anthony Morgan

Ken,
After you have finished sorting the MC out, I would suggest getting a set of speedbleeders from www.speedbleeder.com. I recently fitted a set and after years of spongy brakes I finally had a nice firm peddle. The beauty is that you can bleed the brakes yourself.

Cheers
Ray 77BGT
RM Taylor

This thread was discussed between 02/06/2005 and 05/06/2005

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.