Hi all!
I'm having a severe brake problem with my mini. It's a mk5 998 mayfair
automatic. Sometimes the front right wheel remains strongly braked
although no pressure is applied to the brake pedal. This happened 3
times so far, requiring 3 new disc and pad sets. I've replaced all
master cyilinder and calipers seals and the front pipes with OE stuff,
and the brake fluid is new. The last time the brake effect was so
strong that when I suddenly stopped the car a lot of hot black smoke
came out from the right brake assembly for about 1/2 hour!!
What should I check? Calipers? Master cylinder? Pressure regulator? My
mechanic has no idea, please help!
Thanks in advance for your kind replies

You say you replaced the front pipes. Did this include the flexible
hoses? If not, it is probably the flexible brake hose on the right
side. This would have been my first guess even if you hadn't changed
so many parts.

The inside of the flexible hose can break down and cause it to form a
non-return valve inside the hose. On a brake line this leads to the
pads dragging or locking on. On a clutch line it leads to the clutch
slipping or releasing very slowly.

It is possible to damage flex hoses during installation. Check to see
it has been installed in a twisted manner or if it appears to have
been kinked.

Otherwise, you can break down the problem this way. Since only the
right hand side is affected the fault must lie at or after the point
where the front lines split from left to right.

You probably have a bit more work to do now than just fix the brakes.
If you got things hot enough to smoke for half-an-hour then there is a
good chance that you need to at least repack the right front bearings,
you may also need to replace the seals. The heat could also have
affected the caliper seals and possible the flexible hose.

Here is another possibility. What if the left-hand side flex hose is
weak and balloons on braking. This would mean that when the brakes
lock on the right would get more of the pressure. Both sides would get
hot but the right might get hotter.

I have seen a case where the brake master cylinder pushrod was not
returning far enough. This left one of the fluid reservoir holes in
the cylinder covered. The result was that the brakes would pump up and
never release. Very embarassing on a race course. Lots of smoke and
very little speed. And very hard to figure out.

Cheers,

Kelley

On 22 Mar 2005 08:27:53 -0800, acquaesale (AT) libero (DOT) it (emilio) wrote:

Hi,
I aghree fully with Kelly,
I experienced this exact problem some years ago on a Fiat, and it turned out
to be the brake hose.

Keith

"Kelley Mascher" <mascherk (AT) comcast (DOT) net> wrote

Kelley Mascher <mascherk (AT) comcast (DOT) net> wrote

Yes the flexible hoses have been replaced

Right! I'll have a look

Sorry, what does "to balloon" exactly mean, technically speaking? My
dictionary says it's "aerostato" in italian: you know, that big big
ball with hot air inside with people flying in a small basket!

thanks!

emilio

"to balloon" is the verb form of the big, big ball with hot air
inside, meaning "to expand from internal pressure." In American
English and I suspect in others "balloon" can be a verb meaning to act
like a balloon. Think of the rubber toy balloons that you blow up with
your mouth.

In the case of the flexible hose, it may be expanding (espandere, si?)
due to the brake fluid pressure and losing effectiveness.

Another thing to inspect is the linkage from the pedal to the master
cylinder. It is possible that something is sticking somewhere or is
misaligned.

Is it possible that someone put the wrong master cylinder pushrod in
the Mini before you bought it? A BMC1300 series master cylinder might
have a pushrod that is too long.

Did you drive this car very much before the brake problems started?

Cheers,

Kelley

On 23 Mar 2005 01:27:02 -0800, acquaesale (AT) libero (DOT) it (emilio) wrote:

si, "espandere"

I'll have a look: the radio-cd is very close to the brake pedal
linkage. In the previous posts i've forgot to mention that the problem
has always appeared when brakes were lightly hot (for example the last
time i was downhilling(!) along a crooked road)


I don't think so, the car seems to be 100% original and here in italy
BMC 1300 series are really hard to find (I've only seen one in Rome
area about 15 years ago)

For about 20k Km

ciao!
emilio

hi
i'm sure i saw a post similar to this ages ago ?
it might be worth finding the archives and go through them.

fragged
"emilio" <acquaesale (AT) libero (DOT) it> wrote