Hey Gang,

Well, I went on to "Step Two" which was bleeding the brakes.

It was something I have never encountered. The first one I did was the
right rear: Nothing came out. I had my SO pumping the brakes 5 times, hold.
Nothing. Finally, I got a VERY LITTLE dribble of fluid to come out. But
that isn't right.

Move to the left rear. The fluid SHOOTS out great. After a few more times,
move up to the front right. Fluid SHOOTS out great.

Get to the front Left...Nothing. NEVER a DRIBBLE of fluid.

The pedal goes all the way to the floor. I backed down the driveway to see
how it would stop...I could slam on the brake pedal and it would still move
another few feet before resting.

Obviously, the left front and the right rear aren't getting the
juice/pressure they need. What would this be? Is this for certain Master
Cylinder?

Thanks gang,

ER

"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote

Sounds very much like a seal on one piston in the tandem m/cylinder has
failed.
If the m/c isn't leaking, it'll be the inner set.
M/c needs replacing, or reconditioning with a new set of seals.
Mike.

"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote
Almost certainly the MC. BMW (and almost every automaker) use a
dual-diagonal system, so that if one brake circuit fails, you have a
semblance of balance left-right.

New MC time - I do not recommend rebuilding one.

Floyd

"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote

Thanks All. I looked through the bentley's and it doesn't seem like too
tough of a job on the 1993 740i. The part looks to be about $200US. Any
comments regarding a first-timer doing this task?

On Thu, 16 Dec 2004 05:17:02 +0000, EggRaid wrote:

It isn't a difficult job. Just take care to clean the lines well where
they connect to the Master Cylinder before removing the old unit to keep
from introducing dirt into the circuits. I always leave the brake lines
loose at the master cylinder until I've worked all of the air out of the
new unit. That saves quite a bit of time when bleeding since you don't
have to push as much air all the way through the system and out the
calipers. Be sure to wash off and brake fluid the gets on painted parts,
it can take the paint off if left for a while.

--
The instructions said to use Windows 98 or better, so I installed RedHat.

EggRaid wrote:

<snip>

The brake line fittings at the MC are very soft, and will be damaged
easily if you try unscrewing them with a regular wrench. A flare nut
wrench is an absolute necessity. Don't ask me how I know :-(

STOP.

You have air in your brake lines, and if you do not get it out COMPLETELY,
you will do damage to the braking system and have ineffective brakes. From
the sounds of it, you have a significant amount air remaining in the right
side. You need to repeat your bleeding until the right rear blows out fluid
in a stream like the left rear. All four brakes should blast fluid out just
like you saw from the left rear.

It is my humble opinion that this is not a good job to be doing at home,
especially if you have to ask on a newsgroup. I think you have done some
good work, don't get me wrong. But I still think you have a master cylinder
that is toast, or the portioning valve. Either way, it is my opinion that
you need professional help.





"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote

"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote

MAKE ABSOLUTELY CERTAIN that you Bench Bleed the new MC before you install
it. You will need to purchase (about $5US) a bench bleed kit. This kit will
include fittings that screw in and hoses that go back into the fluid
reserviors. Attach the fittings and hoses, fill the reserviors then FULLY
depress the plunger with a suitable device until it bottoms. Repeat this
until all of the air bubbles stop coming out of the hoses.

The MC will have air inside, bench bleeding will evacuate the air. The
plunger, or piston if you prefer, will not travel far enough with the brake
pedal to push out all of the air, but bench bleeding will have you press the
plunger further than the pedal pushes it.

Leave the fittings and hoses in place while you mount the MC onto the car,
then remove one fitting and attach the brake pipe, then repeat for the other
fitting and pipe. Then bleed the system again until fluid streams out
properly.

Jeff Strickland wrote:
wheels. It turned out that only the bleed fitting was plugged with
gook. After taking the fitting out and cleaning it with a drill bit,
all was fine.

Hello Group,

Thanks for all the replies. I couldn't find a Master Cylinder in any parts
stores--seems they were unattainable by them. So, I called the local BMW
stealer: $541.50. YIKES!

There is a local BMW/Volvo/Saab shop that I use when the job is beyond my
skills set, or beyond my tool set. I gave them a call and they ordered it
and sold me the part over the counter--had it the next day. I saved $200.

Went to SEARS and bought a new flare wrench set. Thanks to RANDOLPH for
pointing that out. I also ran into a vacuum pump for self-bleeding. This
came in real handy since my "Master Brake Bleeder" wasn't home today. Spent
$35 on that.

The removal was a snap, and putting the M/C in wasn't too bad. Sometimes
the wrenches are just too long, or there isn't enough space to get a grip on
the nut, etc. But you work around that stuff.

My Rear Right line had a ton of air in it but I kept pumping the vacuum and
toping off the fluid. Eventually I had them all cleared out and new fluid
abundant, so I got in and checked it out. Pedal felt great. Good brakes in
the driveway.

Took her for a test spin around the block: All is Great! Pedal is nice and
high, brakes are very responsive and what a world of difference.

Again, thanks for all who replied, you helped me tons.

ER





"EggRaid" <shaderushmore (AT) yahoo (DOT) com> wrote