[Top] [All Lists]

Re: More Questions on C Brakes

To: "" <>, " Mike Razor" <>
Subject: Re: More Questions on C Brakes
From: Max Heim <>
Date: Fri, 14 May 1999 10:47:10 -0700
OK, you seem to be eliminating some possibilities at least. I previously 
suggested it might be mechanical interference with the piston or blockage 
in the line. It looks like it's blockage somewhere, either the small 
holes in the master cylinder bore itself or in the brake line(s). Did you 
try disconnecting a brake line at the MC? I think that's what you need to 
do to determine once and for all that the MC is the problem, so you can 
take it up with the rebuilders. If you don't get any fluid out there, 
than you've pretty much narrowed it down. But I'd say it's a fair guess 
that your problem is an improperly rebuilt MC. Either they left some 
debris (decayed seal crumbs?) in the bore (this is most likely), or they 
used the wrong seals and/or piston.

You say you had the MC checked. Was this after it was installed in the 
car and exhibited this problem? If so, and it pumped fluid at that time, 
but you still had the problem when reinstalled, that indicates a line 
blockage elsewhere. You might try disconnecting the line at the MC, 
opening a bleeder screw, and forcing air down the line to see if you get 
any flow that way. If you do, it points back to the MC as the problem. If 
not, you have a blockage in that line. To isolate the blockage may take a 
few more tests at different access points. Perhaps you should first 
visually inspect the metal brake lines for kinks, crushed areas, and rust 
damage (how was the car towed? was it carried on a flatbed? did they wrap 
a chain around the rear axle and crush the metal rear brake line? this 
apparently is common)

I just looked at the diagram of the vacuum servo in Bentley. It seems 
possible that a stuck slave piston could produce the symptom you 
describe. You might want to disconnect the line before the booster and 
see if you can get any fluid out at that point. This could tell you if 
the MC or the servo is at fault.

Sorry I'm rambling a bit. But what you need to determine is the point 
beyond which you have free flow of fluid, in order to isolate the 

Good luck. I'm afraid it will be a bit messy, brakefluid-wise.

BTW to remove the flex hose you first have to undo the metal pipe line 
union nut and disconnect the metal line. Then remove the locknut that 
hold the flex hose to the chassis bracket, and then you can unscrew the 
flex hose from the wheel caliper.

Mike Razor had this to say:

>OK the Beast is sitting in the garage, I have plenty of tools
>and brake fluid.  Spent the better part of two hours jacking
>around with the car.  Tried to remove a flex hose and gave up,
>put an air bleeder on it and cracked open a bled valve ,
>poured the air to it and no fluid exited the system.  Made
>sure the motor was running and I had plenty of vacuum.  M/C
>full of fluid.  Brake is hard as a rock, will not travel more
>than an 1/8 of an inch or so.
>What is stopping it from traveling, what is stopping the fluid
>from moving through the system.  The M/C and boosters have
>been rebuilt and sent back and rechecked.  I am not moving
>fluid from the M/C throughout the system by pushing the pedal
>or with the force of air from an ez bled kit.  It is as if it
>is jammed from the M/C out.  Could be M/ C be bad, and if so
>how can I check it out?
>This is getting to be a real pill, the hardest problem I have
>had with an MG.


Max Heim
'66 MGB GHN3L76149
Runs great, 
looks particularly bad since some SUV clown backed into it.
If you're near Mountain View, CA,
it's the red one with the silver bootlid.

<Prev in Thread] Current Thread [Next in Thread>