Brake Master Cylinder

[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

[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

[Onne]

bubbles eh, I will try that this very moment.

*runs outside, falls over series MM front seats*

[Onne]

*breathes heavily*

I acn't see any bubbles at all, it just squirts if you floor it hard

[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

[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.

[HarryMango]

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

[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

[bmcecosse]

Probably 7/16" AF - but later pipe ends are metric (11mm IIRC) although still 3/8" UNF thread.

[Onne]

so just trial and error then....

[bmcecosse]

Just go armed with two spanners!

[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

[Onne]

I found out today, that the BMC empties itself during the day. What would that indicate?

[aupickup]

ITS KNACKERED

[RogerRust]

a leak

[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?

[bmcecosse]

Yep - more likely to be a leak than a knackered master cylinder.

[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

[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).

[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