Master Cylinder

[Rusty Wishbone]

It looks like my master cylinder requires replacement. Since I have the HiSpec front calipers (& standard rear), I want to stick with the standard MC rather than go for the upgraded one. SJ Sportscars sell one for about £55, but does anyone know of a source of OEM ones please?

[Saltire]

Rusty, I have the one which came out of my S2 when I went to a smaller bore MC. It’s sitting in a box in my garage and was working fine when removed. Would probably benefit from new seals though.

[Rusty Wishbone]

The trouble is that the seals don’t seem to be available.

[M100-NC]

Look at this as a replacement master cylinder:

Original Lotus Part # A100J6082S which was replace with A100J6048S

TRW PMF172
https://www.onlinecarparts.co.uk/trw-2208358.html
Used on BEDFORD,OPEL ...

Probably the same one SJs is offering since the original has been obsolete since 2003

It will replace the original master cylinder but it is steel instead of aluminum.

It has 4 brake line connections. If you only have 3 lines (Left hand drive cars), you just plug the extra port.

They seem to be around 50 to 60 quid.

I have 2 of them in stock and they look like a good solution.

[RonR]

After much cross-referencing I think the BMC seal kits are available - Search for OPEL 1605762 on your favourite auction site.
I have an Autofren D1323 from that search here. However I can't confirm that it fits as I haven't rebuilt my BMC yet.

[M100-NC]

I know of one US owner that sent HIS defective Brake Master Cylinder to White Post Restorations over here and they rebuilt it for them.

[Rusty Wishbone]

Thanks everyone. I'm in the process of removing the BMC so that I can inspect it (its a bugger to get at). If I can replace the seals, I will, otherwise I'll call SJ's for a new one.

[Rusty Wishbone]

Annoyingly, there is what looks like a brake pressure regulator attached to the outlet for the front right brake. It is annoying because it makes both the brake pipe nut for that wheel and one of the mounting nuts for the master cylinder virtually inaccessible. It doesn't appear in any of the workshop manuals - is this a normal arrangement?

[Fredjohn]

No it isn't! I had to replace that pipe (MC to driver's side caliper RHD) and its just a short pipe with a few bends.
Check you have 2 compensators at the rear!
Also are you sure it isn't just a joint? Check other front side too, if you can.

PS no seal kit available for MC. I bought an SJ replacement MC. The Lotus one was available at the time, but not now.

[Rusty Wishbone]

Here is a photo of it:

[Rusty Wishbone]

A few tips for the BMC change:

1. Access to the hydraulic unions & mounting bolts is possible if you remove the power steering reservoir. This means that you can get front access.
2. Buy a couple of flare spanners (10mm & 13mm). They really do make it easier to tackle the hydraulic unions. You can even get ratchet versions, although I didn't try one of them.
3. Check that the pushrod from the servo is in good condition and not scored because this must form a seal as it enters the BMC.
4. There is no seal service kit because the BMC is not serviceable.

If someone wants to add them to the Wiki, please feel free to do so.

[RonR]

Master Cylinder Rebuild kit:

I can confirm that the Autofren D1323 seal kit is correct for the original 22mm aluminium BMC:

BMC-Kit.jpg

Originals below, replacements above.
It all went back together smoothly, but I haven't bled the brakes yet to check operation, as I need to replace a brake pipe.