Morris Minor Owners Club

Declan
From the top of a Minor Lockheed master cylinder filler cap to the top surface of the master cylinder access plate is 4.5mm.
Phil

I made a brass adaptor and cut the thread in the lathe. , It's a BSC thread at 20tpi. I've just measured it and the major thread dimension is 1.105" so I think it is probably notionally 1-1/8". This cap fits and works.

Gavin,
I had a 1.1/8"x20 BS Cycle die here and it would not fit any of the original or the non-vented filler caps I have here. I sent an original to Tracy Tools and they measured it at 19tpi. I also measured it at 19 tpi so I cannot figure it out.
The next opportunity I have I will make up a test piece at 28.4mm OD and 19tpi and see if it fits.

Phil,
That 4.5mm does not leave much room for manoeuvring. Perhaps a copper pipe or a barb at 90° to the hex on the cap would be possible.

Regards
Declan

Declan

That 4.5mm measured is the top of the cap above the master cylinder access plate - not below it.

The cap protrudes into the passenger compartment.

The master cylinder and cap are both genuine Lockheed items.

I have just checked the TPI of the Lockheed filler cap and it is 20TPI. A 19TPI is nearly there but does not fully match the cap thread profile.

The cycle thread profile is virtually the same as UNS (Unified National Special) which is of Whitworth form except for the root and tip of the thread & which is used for various threads on the Minor. So one may fit the other but not the other way round.

As expected the ESM non vented cap fitted the genuine Lockheed master cylinder without any problems.

Phil

Well I have been busy with work lately but on attempting to bleed the brake system I have hit a wall and would like some advice.
If I open the master cylinder and depress the brake pedal I can see fluid being forced out of the cylinder.
Does this point to a leaking seal within the master cylinder?
The master cylinder I have is a new genuine lockheed item but could one of the seals have perished in storage?

Regards
Dermot.

Dermot
When you remove the master cylinder filler cap and depress the pedal you can expected to see movement of brake fluid inside the master cylinder which is a reaction to the fluid being displaced around the brake system by the master cylinder piston.

Do not fill the master cylinder higher than 1/2" below the filler cap threads.

The main test is to press the brake pedal down and hold. If there is no downward movement of the brake pedal the system is sound.

Phil

That may be my issue, in one of the manuals it states to fill the master cylinder to the bottom of the thread for the cap,maybe my cylinder is over full.
I will try persuade my wife to pump the pedal for me again.
Thanks for the information thus far.
Dermot.

The BMC manual (Fig. M.2) states that the brake fluid level should be 1/2" below the bottom of the filler cap threads.

Ignore all other specifications quoted.