Brake Master Cylinder Reservoir bungs

[anonymous-user]

Hi all,
I am recomissioning a Mk4 Cortina and have rebuilt the Girling brake master cylinder with all new rubbers. Unfortunately trying to fit the plastic reservoir to the cylinder was near on impossible. The bungs/bushes that fit into the top of the cylinder must be a really tight tolerance to the reservoir stubs as the rubber ended up getting slightly damaged with many attempts to push the reservoir in.

I filed down the tangs on the reservoir stubs so they were not as sharp and eventually got it to fit but when bleeding the system all was going well, but then the master cylinder stopped getting any fluid. I am assuming a bit of rubber has come off the bung and caused a blockage but could it be something else?

Also I am assuming that these bungs never have any real pressure on them as it's a gravity fed reservoir?

I think I will have to file down the tangs a bit more to get an easier fit.

Finally is there a better lubricant I can use to help the reservoir fit than brake fluid?

Thanks for any help in advance!

[B1G M4TT]

You say that fluid isn't getting through but it might be that the piston has stuck when you pressed the pedal due to traveling further than it normally does when the system has pressure in it. This could be because the bore has corroded past normal piston travel.

Was there not a rubber grease sachet that came with the seal kit? That would be ideal for lubing the reservoir.

[anonymous-user]

Thanks, that's a good point I hadn't thought of.

I have today taken the cylinder apart and found that the bungs for holding the reservoir appear to be too deep and one has even bottomed out on the piston retaining pin. I will trim the depth of these a little as I think these may have been partly covering the holes into the main part of the cylinder and starving it of fluid.

There wasn't any grease in the kit. I guess this could be a sign of a cheap repair kit which could explain the overly deep bungs. I'll get some from the motor factors.