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MG MGB Technical - Brake bleeding issue

Sorry folks, this isn't specifically MGB related but I've found the knowledge base of this board second to none so here it goes:
In short I've been building a 1988 Ford Escort GT budget beater race car.

I just attempted to bleed the brakes (power brakes)on my 88 GT and had a couple of issues.

I went around the car once with the engine off, working back to front, then did another couple passes with the motor running.

The right rear and left front were being stubborn. When my partner went to pump the pedal he would get maybe one pump then the pedal would firm up. This is with the bleed nipple wide open. On the left rear and right front when he pumped it flowed fluid just like normal. We were able to get an ok pedal, but it doesn't become rock hard until about 1/2 way down in the travel. I don't usually work with power brakes so maybe that's just how cars with power brakes go, but I would like the pedal to be rock hard closer to the top.
All four wheels seem to lock up when the brake is on and free up when it is off, so I don't think its a bad slave cylinder/caliper.

I believe the left front and right rear on the same line out of the master cylinder.

Any other help to figure out this problem would be appreciated.


-Bill M
Bill Mertz

You may be having a problem in the master cylinder section feeding the right rear and left front. Power brakes when used with the engine running normally will not feel "rock hard". With the engine off, and the reserve vacuum used up with a few pumps of the pedal, you should then have a hard pedal. I doubt that you have them but anti-lock brakes require special tools for bleeding.
John H

When the motor is off it actually has a pretty hard pedal. And correct there is no anti-lock brakes.
I may try and compress the rear slave and front caliper piston to see if it will dislodge the blockage.
Otherwise new master maybe.
Bill Mertz

If it's got split braking try opening one bleed nipple on each circuit if you are bleeding with the pedal. Otherwise use a continuous bleeder like EeziBleed. But that would usually only be needed if you had air stuck in one circuit, which would normally be revealed as one circuit locking the wheels but not the other. If both circuits are locking - at more or less the same pressure - then the brakes themselves seem to be OK, and it would seem to be down to perception.

Brake servos usually result in a longer and softer pedal, but lower pressure to lock the wheels. Some people prefer a harder pedal even if it needs more leg pressure to lock the wheels, and personally I find some cars have way too much assistance. On a competition car, when you are having to put some physical effort into getting the thing round the track, having very sensitive brakes seems counter-intuitive, but then you can get used to anything. I don't know about an Escort but on the MGB having the rear brakes incorrectly adjusted will result in a *longer* pedal. But if the Escort has self-adjusting, and they are working properly, that shouldn't be the case.
Paul Hunt 2

Did you replace the flex lines?
Are the rear brakes properly adjusted?

The following forum seems fairly active.

This thread was discussed between 24/04/2008 and 26/04/2008

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