18 replies to this topic

[beardylondon]

Hi All

 

So my Mini is a 1966, but when it was rebuilt back (by us) in the 90s we updated some bits, as it was never going to be concours. The car has 10" discs and no servo and the later master cylinder.

 

To be honest, it's so long ago I cant remember much about what we did, so I've taken some pics, as basically the brake limited valve (first photo), is now leaking. From searching the forum you cant rebuild them, so I need a new one.  There is also what looks like a brake pressure regulator valve on the rear subframe (third photo), but only fitted upto 1969 according to Spares. So it seems odd I have both, if we updated everything to later spec, especially as the brake limited valve was only fitted rom 1978 onwards.

 

I've looked a few diagrams, but can't find what I have.

 

Thoughts, as I am keen to know if its worth replacing the brake pressure regulator valve at same time, or if this isnt needed?

 

Edited by beardylondon, 29 June 2026 - 04:07 PM.

[Spider]

I've moved your thread to Problems, Questions and Technical as it's a more appropriate place for it.

 

The Bulkhead Valve is a later one you would have fitted when you did your rebuild, the one in the rear subframe is the original early valve.

 

You only need one of these, though there's little down side to having both, only that there's more rubber and springs in the system than is needed, so would have a higher pedal travel and a more spongy pedal feel than otherwise could be had.

That type of bulkhead valve IMO are not great, considerably more complicated than need be and as you've already mentioned, can't be rebuilt, though, once any cylinder starts leaking, that's the end of the road for them. Also, because of their design, there is a part of the cylinder that is always open to atmosphere and so prone to rusting.

The set up will work just fine with the original valve and given a choice of the 2 that's the one I'd run with. There are kits available for these, though you usually need look at the likes of ebay to find them.

[beardylondon]

Hi Spider,

Thank you as always for the speedy and expert insight!

First off, I believe the brake pressure regulator valve could be the original from 1966, as I don’t remember replacing it, or it would be a 1999 replacement part. However this could explain why the brakes are hard to bleed and the rear brakes only just used to pass the MOT, when the vehicle still had to have one.

Hence if the brake pressure regulator valve is 27 or 60 years old, it must be at the end of its serviceable life?

I wasn’t 100% sure what you meant, but it seems like I have 4 options:

1 - Replace the leaking brake limiter valve only, keep original brake pressure regulator valve.

2 - Replace both brake limiter valve and brake pressure regulator valve.

3 - Delete Brake limiter valve and replace brake pressure regulator valve.

4 - Replace brake limiter valve and delete brake pressure regulator valve.

Thoughts?

[Spider]

Sorry if I wasn't clear.

 

You do have many options here, some that you've short listed.

 

If it were me, I'd delete the (4 way) Valve you have on the Bulkhead and either overhaul or replace the one you have on the Rear Subframe.

[beardylondon]

Spider, that makes sense to delete that brake limiter valve on the bulkhead and replace one on subframe. I guess I just need to join the brake pipes with a in line unions
However I’m going to need a bracket to secure the brake pipes to the bulkhead, I’ve just had a quick look and couldn’t see anything, might have to make it, unless someone knows the part number?

[Spider]

Have a look at the likes of Car Builder Solutions, you might find something there;-

 

https://www.carbuild...ng-clutch-parts

 

The threads in that Bulkhead Valve are M10 x 1.0.
 

Also, it might be practical to replace the pipe that's for the front brakes, I get that for the rears is a different story. I'll add that in the factory cars that had in-line joiners used, they were all unsupported. I used to feel that they should be, but in the Mokes, they all have at least 2 joiners, unsupported in horizontal pipe runs, and having taken them over many of our horrid corrugated tracks, I haven't experienced any issues from that set up.

[beardylondon]

Thanks Spider, good info, much appreciated.

[beardylondon]

So it looks like this will work:

 

https://www.carbuild...e-to-m10-female

 

I removed the brake limiter valve in the bulkhead and there is definitely enough pipe to join the two and so a bracket may be overkill.

 

Spares say they do them too:

 

https://www.minispar...onnector-metric

Edited by beardylondon, 30 June 2026 - 01:41 PM.

[Spider]

I thought I'd put up the Car Builder link as they also have tube clips.

If you have flaring tools, you can swap out one of the Male Tube Nuts for Female and then on flaring the tube again, put an Invert Flare on that side, screw them together and that's another method of joining the pipes.

 

[beardylondon]

@Spider

 

So I have deleted the bulkhead valve and used 2 joiners (see photo), and you were right, I didn't need a bracket, seem very sturdy.

 

I have also installed the new brake regular valve (21A1774) on the rear subframe. I cant see any leaks anywhere.

 

 

I also decided to install speed bleeders and have topped up the brake fluid with fresh DOT4.

 

I started the bleeding process and I cant get any fluid out of the rear N/S cylinder.  I've tried all the things I've done in the past, 50 odd pumps on the pedal and nothing. Not sure what I've done wrong here!

Edited by beardylondon, 07 July 2026 - 01:36 PM.

[Ethel]

Is the front end photo with the unions nipped up? Looks like you'd have room for some half nuts to make up a support bracket or 2.

 

It might be you're tripping the brake limiter as you bleed the rear. Go very gently on the pedal - I don't know how much pressure would be needed to open you easy-bleeds, but it's bound to be more than a plain nipple. I use a syringe to suck on the nips when I'm bleeding 

[beardylondon]

Yes front end unions are fully nipped up.

Is the front end photo with the unions nipped up? Looks like you'd have room for some half nuts to make up a support bracket or 2.

It might be you're tripping the brake limiter as you bleed the rear. Go very gently on the pedal - I don't know how much pressure would be needed to open you easy-bleeds, but it's bound to be more than a plain nipple. I use a syringe to suck on the nips when I'm bleeding

[Spider]

That sure looks neat enough !

 

It maybe that the flexy hose has started to collapse internally ?

Try 'cracking' the tube nuts 1/4 of a turn working you way back from the wheel cylinder to the valve while bleeding to see where it's blocked.

[Shooter63]

You might want to try one of these bad boys, they have been a life saver for me before, freely available via various online outlets.

 

Shooter

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[beardylondon]

Thanks both, I will explore these avenues and report back!