Opinions on master cylinder bore

[chrisd87]

Hi everybody,

As part of its recommissioning I'm currently rebuilding the brakes on my 1970 2dr, which has stood since 2009. The brakes seemed to work OK, but the rears were stuck on, so I've decided to do a full brake stripdown to check the condition of the whole system. Not good so far - looks like all the wheel cylinders will need replacing, as they're rusted inside.

I just wanted to ask for people's opinions of the master cylinder - it's in much better nick than the any of the wheel cylinders (and seemed to be working fine), but on stripping it down it appears there's some pitting and a spot of corrosion near the 'mouth'. Does this amount of corrosion write the cylinder off, or would it be OK just to stick some new seals on it (it's a Lockheed cylinder, probably the original)? I've attached some pics. These are the best I could get, unfortunately.




Also, does anyone know how to remove the valve at the very end of the cylinder? If I re-use it, I'd like to give it a very thorough clean, as there's rather a lot of black sludge in the bottom of the fluid reservoir.

Many thanks.

[bmcecosse]

Sorry -but I would fit a new one.

[Trickydicky]

I would just replace it too, it`s no fun having to fit the new seals, refit the M/C back in the car, bleed the brakes to find it still leaks and then have to take it all out again.

[IslipMinor]

I would definitely fit a new one. Getting it out and putting it back once is enough!

[chrisd87]

Thanks for the replies everyone. Looks like it'll have to be a new one then - this is quickly getting expensive!

[Fingolfin]

It can be impressive the difference a new master cylinder makes, though. Worth the money in my opinion.

Mog had its original master, and the brakes wouldn't retain pressure for more than a day or two, and after a month the pedal just sank right to the floor. It was due to corrosion in the bore, which was tearing up the seals; replacing the seals made a difference the first few pushes, but then of course the new seals got torn up.

After replacing the master with a brand-new Lockheed one, I haven't had a drop in pressure at all, even six months on. The system retains all its pressure, even from the first pedal-push.

[rayofleamington]

Firstly - Great pictures, well done!
The damage shown is pretty severe, and it's not far from scrap (as per all previous comments - it needs replacing)

Secondly - the damage that can be seen in the pictures is in the region of the secondary seal. This will lead to a gradual loss of fluid into the chassis leg and when it's very bad leads to gradual air introduction into the pressure side (i.e. spongy brakes).

For reference - the primary seal (the one that does the braking work) is further down the bore at the other end of the inner valve slide. The NRV at the output end can usually be removed by poking a rod through from the T-piece end.