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Brake Master Cylinder
Posted: Thu May 25, 2006 6:16 pm
by Onne
I was driving along toady, and my brake pedal went down too far.
So I looked at the level of DOT4. There wasn't much of a level.
So I expected one my BCs to be leaking. I have taken off all the drums, and everything was dry.
Which leaves only the BMC.
There was a lot of fluid in the chassis leg, but I couldn't define if it was water or BF.
So I took some piccies:
It sure isn't clean or anything, but I don't feel that much like changing it, since it is not one of the nicest jobs
Onne
Posted: Thu May 25, 2006 6:23 pm
by rayofleamington
Fill it up with brake fluid and bleed it off a little - then if you still see bubbles rising into the reservoir (I think you will) that doubley confirms what you already suspect

Posted: Thu May 25, 2006 6:30 pm
by Onne
bubbles eh, I will try that this very moment.
*runs outside, falls over series MM front seats*
Posted: Thu May 25, 2006 6:34 pm
by Onne
*breathes heavily*
I acn't see any bubbles at all, it just squirts if you floor it hard
Posted: Thu May 25, 2006 6:35 pm
by rayofleamington
I acn't see any bubbles at all, it just squirts if you floor it hard
In which case, double check that the master cylinder T-piece / pipes connection isn't leaking (Easier said than done) but that is the other way you can get empty m/c and fluid in the leg.
ps - fingers crossed

Posted: Thu May 25, 2006 6:39 pm
by Onne
I will keep my fingers crossed, and I might have a peak at the T-piece. If it is the latter, how much of a swine is that to replace?
You all did notice both of my pedals being inside the leg?! Lovely isn't it.
Posted: Thu May 25, 2006 7:26 pm
by HarryMango
Onne wrote:I will keep my fingers crossed, and I might have a peak at the T-piece. If it is the latter, how much of a swine is that to replace?
You all did notice both of my pedals being inside the leg?! Lovely isn't it.
Hi Onne
I had the same problem last year & it was just a loose pipe connection into T-piece. Mine just needed tightening - if you have to replace this then it's not really a problem apart from lack of spanner swinging space - about 1/50th turn at a time so takes forever
Rog
Posted: Thu May 25, 2006 8:07 pm
by Onne
Will check if they are tight. What size are those? And how tight should they be. The last thing I want to do is ruin them
Posted: Fri May 26, 2006 8:56 pm
by bmcecosse
Probably 7/16" AF - but later pipe ends are metric (11mm IIRC) although still 3/8" UNF thread.
Posted: Fri May 26, 2006 9:00 pm
by Onne
so just trial and error then....
Posted: Fri May 26, 2006 9:09 pm
by bmcecosse
Just go armed with two spanners!
Posted: Fri May 26, 2006 9:25 pm
by Onne
I will indeed!I will try and see if there is any slack. I do understand that even the slightest looseness can be a problem, since it use pressure to operate
Posted: Sat May 27, 2006 7:14 pm
by Onne
I found out today, that the BMC empties itself during the day. What would that indicate?
Posted: Sat May 27, 2006 7:56 pm
by aupickup
ITS KNACKERED

Posted: Sat May 27, 2006 8:09 pm
by RogerRust
a leak
Posted: Sat May 27, 2006 8:16 pm
by Onne
it has passed away. Oh bother. I have ordered a new one. I will grind the old bolts, and fix the new one with special nuts.
Oh why?
Posted: Sun May 28, 2006 10:17 am
by bmcecosse
Yep - more likely to be a leak than a knackered master cylinder.
Posted: Sun May 28, 2006 12:07 pm
by Onne
Ity might be the copper washers in between the banjo, at the back of tghe cylinder.
If I were to replace these, would that mean a lot of bleeding? Or wil there still be a lot of fluid down the lines?
This because I don't like bleeding brakes
Posted: Sun May 28, 2006 10:19 pm
by rayofleamington
If it leaks out when not in use then it is much more likely to be a corroded bore in the m/c than a leaking T-piece. The lack of any bubble is a bit odd though.
If a leak at the T-piece was big enough to allow that much leakage at almost no pressure then you would notice a very 'non-firm' pedal (ie the pedal would go to the floor if you kept your foot on it for a while).
Posted: Sun May 28, 2006 10:24 pm
by Onne
And with a knackered bore that wouldn't happen? Because my pedal is firm, and doesn't go down to the floor when pressed hard for a while.
I does need a second pumping to work right, but I blame that to the air, which will be in the system now