How many times has he pumped the pedal? If he pushed all the pistons right
back into the calipers before fitting the new pads that could take several
pumps to push them all into contact with the disks.
Where are all the pads in relation to the disks? If one or more pads have
clearance to the disk then there is no (or insufficient) pressure in the
system - at that corner, at least.
>From an MGB perspective, if the system is full of fluid and there are no
leaks, either visible on the ground or a dropping level in the m/c, then
there must either be air in the system or the m/c is leaking back. However
if the m/c has been changed, that leaves air in the system. But changing
the m/c *will* have introduced air into the system, so maybe it is a
combination of insufficient pedal pushes in the first case and air in the
system now.
If the brakes were working fine before the pads were changed, and that is
all that was done originally, then IMHO there is more to be lost than gained
by willy-nilly changing parts - he is just introducing more variables. You
say he can find no leaks "to speak of", what does that mean, there is a leak
but it is a very small one? There shouldn't be any at all. When bleeding,
he should be looking for air bubbles in the fluid (or rather, a lack of
them). He may have to employ several methods of pedal pumping to shift all
the air, or an Eezi-Bleed or similar. I would concentrate on that before
changing anything else.
Finally, not that it's much help now, if he considers the pressure that is
in the braking system in an emergency stop, and the leverage effect of the
m/c and calipers, there is no way anyone is going to damage the m/c by
putting pressure on a caliper.
Good luck,
PaulH.
----- Original Message -----
From: Mike Lishego <mlishego@asheboro.com>
To: MG List <Mgs@autox.team.net>
Sent: Friday, January 07, 2000 2:35 AM
Subject: Bizarre non-MG brake problem
> Hello all,
> I'm begging the advice of the experts on this one. A friend of
> mine just replaced all four wheels of brake pads on his Daytona.
> All he did was remove the pads and put new ones on, and he suddenly
> found his brake pedal going to the floor.
> Thinking that the pressure he put on the caliper pistons may
> have damaged the old master cylinder, he bought a new one and
> installed it. The master cylinder had good pressure when he bench
> bled it, but it fared as poorly as the old one. Apparently, even
> when he pumps the brakes, the car does not gain pedal pressure.
> He bled the lines quite a few times, and he can find no leaks to
> speak of. The car has a power brake booster, and after testing it
> still holds pressure with no leaking. He was thinking his
> proportioning valve may have gone, but I suspect a faulty hose
> somewhere. Since we can't find any dripping fluid, he's less than
> thrilled about the idea of buying four new rubber hoses for the car.
> Anybody have any ideas?
> (The car has four wheel disks and no ABS, BTW.)
> Thanks!
>
> Mike Lishego
> http://www.mgb.bc.ca/virtualgarage/
> 1991 Mazda Miata
> 1986 Plymouth Turismo T1
> 1984 Mazda RX-7 GSL-SE
> 1974 MGB
>
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