Hi all, I have a question regarding both brake and clutch master cylinders on MK2 Cooper S. (Plastic res type)
A friend mentioned that MK2 were steel, and there was a switch to alloy for the Clubman. Can anyone advise, and, if possible, indicate where I could pick up a pair?
Thanks


Sent from my iPhone using Tapatalk

Hi,
Have an Oct-69 build Mk2 S, brake master is larger metal type and clutch is plastic reservoir type. I believe this arrangement is correct for this period.
Also have a Sept-70 build car where both cylinders are the plastic reservoir type, they may have been replaced, but I have seen this arrangement on cars of a similar age.
I have used the cylinders which came with the cars when purchased and they have been re-sleeved as necessary.

_________________
Clive G
1969 Mk II Cooper S
1970 MK II Cooper S
1963 Triumph Spitfire
1982 RX-7 Series 2

I have no doubt the masters are supposed to be the plastic reservoir type for my car.. my question is, should the master body be alloy, or cast steel?
I was under the impression that the clubman had an alloy body, and the earlier one as seen on MK2 S and Mini K had a steel body?


Sent from my iPhone using Tapatalk

It's a oood question and one worthy of some research. The plastic tank master cylinders are Lockheed brand, but supplied to BMC by BAI (Sydney). The drawings for these parts are therefore somewhat third hand by the time they got to BMC and the only drawings avialable are assembly drawings of the whole thing assembled. The BMC drawing is a trace of the BAI drawing which in turn is a trace of the Lockeed drawing. The entry for "Material" says "Proprietory Item" - meaning BMC took whatever came to them from the outside supplier. However, there is a note on the last revision to the drawing which says (dated 4/8/1972) "Material change cast iron was aluminium alloy" which seems to imply that the early ones were alloy and the later ones were cast iron. Regards, Tony

I had looked into the change points a while ago but got side tracked so this is all I have so far.

Car 636, 839, 1002 - tin brake and clutch master cyls

Car 1119, 1237, 1309 – tin brake and cast iron body/plastic reservoir clutch master cyls

Car 1420s - plastic reservoir brake and clutch master cyls. (SLL52 quotes chassis 924 but should be body 924)

Car 1675, 1732, 1866, 2068, 2164, 2344, 2851, 2855, 2883 alloy body/plastic reservoir brake and clutch master cyls.



I can try to narrow it down a bit further but alot of cars have been messed with or restored so I cant be sure of the exact change point.

Based on Tony’s post, it looks like I need a pair of alloy master cylinders with the plastic reservoir - are these available? New or S/H..


Sent from my iPhone using Tapatalk

Thanks GTO, some great info there.I appreciate your work but my car has been rebodied, so there’s no need to go into deep analysis on this, so my body numbers won’t line up. I’d just like it to be close as possible to be period correct.
Cheers


Sent from my iPhone using Tapatalk

Just to confuse gtogreen's data, my 8/'70 S (car 2375) has cast iron clutch and brake cylinders. Have owned the car since 1975 so a good chance these are original. My memory agrees with gtr's impression that the alloy bodies came later.
A while back, "Guam man" on this site, had trouble locating a pair for his GT.

The plastic reservoirs and caps are available from minisport aus in Adelaide. The alloy bodies will need to be sourced second hand and then resleeved, reconditioned nd all new seals fitted. It is an expensive exercise but doable which is why most opt for new masters.
I may have a couple here if you cannot find elsewhere. Need to find them though.

_________________
Cheers Dave.

Thanks Steam, that would be awesome. The studs on my pedal frame/box (whatever you call it) are longer to accommodate the thicker mounting base on the cylinder. Based on the posts above, it would appear that the body material is a bit hit and miss, so I’m not really too fussed about having either cast iron or alloy.. as I mentioned earlier, my car had been re-bodied. I would really appreciate it if you could have a look when you have some free time, we can liaise via PM maybe?
Cheers, Tom


Sent from my iPhone using Tapatalk

I will have a look when free time permits.

_________________
Cheers Dave.

The plastic tank cyls with the large fluid cat was made by 2 companies.
Girlock in Campsie in NSW and PBR.
One was alloy and the other was cast iron.

Overhaul kits are available as are the tanks and caps.

Parts books and drawings all showing Lockheed, Girling or Girlock part numbers for master cylinders for Mini right up to split systems. The PBR brake booster was fitted to MKII Cooper S, but as far as I can tell that's the only PBR component in a Mini brake system as a factory item. In Service Bulletin C35/70 it is mentioned that the master cylinder had now been upgraded with an anodising treatment which of course would only apply to an aluminium alloy part. As mentioned previously, in 1972 there is an mention of a change from alloy to cast iron for the Lockheed part so this anodising in 1970 is consistent with that date. PBR probably made a service replacement.