346 replies to this topic

[Retro_10s]

I'm very surprised you got that apart at all!
The piston in mine has rusted solid to the bore, then plastic tank snapped off, was very brittle.

I was surprised too, Colin! the tank was very very hard to get off,.. it felt as though something else needed removing to allow it to pop away from the cylinder body and like you, I was pretty sure the tank would break. But I got away with it!

Edited by Retro_10s, 29 September 2022 - 06:51 PM.

[GraemeC]

The correct pin is CLZ512.
That one looks more like the one for the top of the clutch arm.
I don’t *think* it would foul the pedal box, but I think I’d prefer one that couldn’t walk sideways.

[Retro_10s]

The correct pin is CLZ512.
That one looks more like the one for the top of the clutch arm.
I don’t *think* it would foul the pedal box, but I think I’d prefer one that couldn’t walk sideways.

Totally agree with you there. I've just checked the bag they came in and I have got CLZ518. Maybe I can use them elsewhere as you say. Thanks for the part number! Luckily these bits are inexpensive eh! Cheers

[Retro_10s]

A little messing about today, I've decided to rebuild the brake master-cylinder I have, so while I wait for the parts to arrive I set about sanding, scrubbing and degreasing. Now it's etch primed.


Then I decided to whip a front wheel off and see what condition things are in. Bottom arm bushes are toast, but the rest of it appears okay and the underside of the panels is in fine shape, amen.

Cooper S 7.5 setup, barely used really, discs are fine, calipers fine, pads fine (I suspect I should replace these pads, they're barely used but are now a decade old,.. what say you?)

I may give calipers a layer of silver paint since they haven't rusted yet, and I want to replace the front hoses too.

Just out of interest I thought I'd chuck a wheel on to see if they really do fit. These are 10" rostyle wheels, with the correct offset to fit over the 7.5" disc setup archless. They fit with about 2-3mm space between the caliper and rim, tight,.. but it fits. Very happy about that.

Edited by Retro_10s, 01 October 2022 - 03:28 PM.

[GraemeC]

I'd say the pads will be fine.  Just whip them out, maybe lightly scuff the surface with some course sandpaper (assuming they're not that old they're asbestos - but still watch the dust), wipe of copper slip on the back and replace.

 

Once you've got the system back together I'd push the pistons out and just make sure they're nice and free in the calipers.

[Retro_10s]

I'd say the pads will be fine.  Just whip them out, maybe lightly scuff the surface with some course sandpaper (assuming they're not that old they're asbestos - but still watch the dust), wipe of copper slip on the back and replace.
 
Once you've got the system back together I'd push the pistons out and just make sure they're nice and free in the calipers.

Thanks for that pal, the pads were new a decade ago and I probably put less than 500 miles on them before laying the car up again cheers

[Retro_10s]

Today I've been trying to convince the brake master-cylinder to go back together. I have bought seal kit GRK1035 and I'm not impressed, either they 'dont make them how they used to', or I have a bad kit,.. 2 of the seals fit well, the other two don't really match up to anything, and one of the thin seal washers doesn't match up to anything. I'm unsure where to go from here, I believe I have the right kit for my yellow tag cylinder, GMC227. All four seals are different yet two of the OE seals are identical ...

After looking at diagrams online, comparing old Vs new, and measuring the seals + the various stepped piston diameters I have installed the seals the best I can. The first piston seal slides in with a satisfying gentle pop, but the second seal is such a tight fit in the cylinder that it's trying to slide off the piston, I am using way WAY too much effort, something is not right,


The seal on the right is causing a lot of grief. I've stopped trying to install it now, as I am certain I will damage it, confusing. Swapping it for a different one would mean the other seals fit even more poorly on the piston.

[GraemeC]

Your piston looks different to the one shown in the MS repair kit for a GMC227:

http://www.minispare...|Back to search

 

 

I wonder if you need this kit?:

http://www.minispare...|Back to search

[Retro_10s]

Your piston looks different to the one shown in the MS repair kit for a GMC227:
http://www.minispare...|Back to search


I wonder if you need this kit?:
http://www.minispare...|Back to search

Ah now that's interesting, I wonder

My mini is a C plate 85, so it's right on the changeover from the older type master cylinder (I think)

Would this explain why I'm unable to see the stepped bore that I was expecting to inside the cylinder? Perhaps I have a GMC195 cylinder.

Edited by Retro_10s, 05 October 2022 - 03:44 PM.

[Colinmac1330]

I think if you look at your inlet pipes sizes they are the wrong way round from the GMC227 Yellow band cylinder so to me this is a pre-GMC227.

[Retro_10s]

I think if you look at your inlet pipes sizes they are the wrong way round from the GMC227 Yellow band cylinder so to me this is a pre-GMC227.

Yep I think you and GraemeC have identified the problem here. The difference in piston shape and the seal sizes look pretty much perfect on the GRK1016 kit. Thanks for taking the time to chime in here, I appreciate it!

It looks as though the crossover date to GMC227 was May 1985,... This mini was registered in August 1985 so either it sat at the factory awaiting registration for a few months, or perhaps they were still working down through old stock of the older type!

Cheers.

[1984mini25]

Without looking properly (so sorry if I confuse or repeating anything) With mine being an 84, but one of the first with disk brakes they used the same yellow band master cylinder for both drums and disk brakes. With the top of the master cylinder feeding the rear brakes and the bottom one feeding the front.

 

But in Nov 85 a new stepped bore/yellow tag master cylinder was used witch have the feeds for the front and rear brakes the other way around and different internal bores. From what I'd found it was more to do with the standard fit 8.4 disk brakes, and requiring more pedal effort than with the servo effect with drums. 

 

This is also the only master cylinder available, so for fitting to anything pre Nov 85 the pipes need switching round (there is a kit available) as failure to do so sends the braking force that would normally go the front to the rear brakes and reduced rear braking to the front. 

[Retro_10s]

Without looking properly (so sorry if I confuse or repeating anything) With mine being an 84, but one of the first with disk brakes they used the same yellow band master cylinder for both drums and disk brakes. With the top of the master cylinder feeding the rear brakes and the bottom one feeding the front........

My city originally had the 8.4 setup on the front, and as far as I can tell the master-cylinder is the original, so hopefully a rebuild kit will suffice now that we have potentially identified the issue with parts. Should I have to replace the cylinder I'll be sure to revisit your advice on switching the pipes.
Cheers.

[1984mini25]

 

Without looking properly (so sorry if I confuse or repeating anything) With mine being an 84, but one of the first with disk brakes they used the same yellow band master cylinder for both drums and disk brakes. With the top of the master cylinder feeding the rear brakes and the bottom one feeding the front........

My city originally had the 8.4 setup on the front, and as far as I can tell the master-cylinder is the original, so hopefully a rebuild kit will suffice now that we have potentially identified the issue with parts. Should I have to replace the cylinder I'll be sure to revisit your advice on switching the pipes.
Cheers.

 

 

I've got the lengths and what fittings are need each end if you prefer to have them made up over the conversion kit, as it's something I've recently had to do to mine. 

 

As over the first lockdown to keep myself busy I decided to clean up and repaint the master cylinder area, expect when I came to refit and bleed up the master cylinder I had nothing working on the front until I tried using an eezibeed kit. Witch then got the front brakes working closely followed by the seals in the master/reservoir failing and covering everything/bulkhead in brake fluid. 

 

The brakes had been pretty rubbish prior to lockdown, were at the start of a drive the brakes would be ok, then feel like brake fade, but would still stop with a long pedal until parked up and left overnight. 

 

Only at some point in my minis past prior to my ownership the original master cylinder had been changed, but rather than change the pipework to suit the new design of master cylinder, What they had done was to chop off and replace the one fitting (m12 I think) of the original pipework and bend/bodge it to fit. 

[Retro_10s]

Cheers Karl! Will bear that in mind

I didn't have any problems with the brakes when the car was on the road, but of course i decided to refresh the hydraulic systems as part of the overhaul,.. fixing what ain't broke lol!