When people talk about brake lines calapsing they do not mean that they just
calapse and you cannot gravity feed brake fluid through them. They mean that
when the master pulls fluid back, the brake line calapses preventing the
brake fluid returning to the master. Sorta like when your trying to suck an
ice cold milk shake through a straw and the straw calapses. Stop sucking on
the straw and it opens up again. So, this could still be your problem.
Another possibility is water in the caliper. Although, you are using
silicone, water may have entered the system somehow. As you brake the
caliper heats up until the water boils off producing vapor which can cause
binding but usually just creates a mysterious spongy pedal which disappears
when the calipers cool down.
The third possibility is that you rebuilt your calipers with new seals but
did not replace a worn piston which could be binding. I would say that your
best and cheapest bet would be to replace the front hoses and rebleed the
system. The warning light is a good clue that maybe someone else could pick
up on. Maybe there is a problem in the master.
Chris Reichle
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From: mgs-owner
To: mgs
Subject: Brake bias/proportion?
Date: Monday,February 17,1997 1:37PM
Ok, I have a braking problem that I havent been able to sort out.
I have an idea of what *might* be wrong, but I wanted to bounce the
problem past the list before I run off any buy new parts.
Here are the facts:
73 MGB, dual circuit brake system, rebuilt calipers, rebuilt master
cylinder (both rebuilt by me), new wheel cylinders, new brake lines,
hoses, pads and shoes. All components were replaced or rebuilt.
I am using DOT5 brake fluid (silicone).
Here are the symptoms:
After driving for about 10 mins, both calipers begin to drag, the
pressure differential warning light turns on (and remains on) and
eventually the front brakes grab- you can smell the pads heating up.
If I let the car sit for about 15 mins, the P-D-W goes out and the
process repeats again. The pedal is always firm; and there are no
obvious leaks, although I have noticed a tiny spot of fluid on the
drivers floor mat, (about the size of a quarter). I attributed
this to a loose fitting (or a drip from the pedal box due to a sloppy
filler :-)
I know what you are thinking- no, I am not driving the car on
public streets like this; these are just test runs on private
property. Also, the rubber brake hoses are *not* collapsed,
I could gravity feed new fluid through them when I installed
them a few months ago.
I suspect that the master cylinder is not distributing fluid to
the rear circuit; but I am not sure how this could cause the
front brakes to bind- I would have expected the front to work
fine, but the rear to not work at all. Any ideas??
--Scott
Scott Hower --> howersl@ttown.apci.com
Air Products & Chemicals, Inc.
7201 Hamilton Blvd Trexlertown, PA
(610) 481-2646
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