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What would you do? Just rebuilding the brake system on a car that has not been used for 20ish years would you keep the original master cylinders and rebuild them or ditch them for new! I have had a bad experience with a new brake cylinder recently.

David

I did a very low mileage car which sat for 22 years, 3 years ago. I decided to chance them as they were still working.
It's only doing short runs in the summer but I have had no problems.

I personally, dont like fitting replacment seal kits, I fit new replacement cylinders for reliability.

Hi David,

Never had any bother with rebuild kits so long as the bore is in good shape. New cylinders are good, but NOS cylinders can be a pain when the original preservative turns into a sticky goo which blocks the ports etc.

Scotchbrite in a piece of split rubber hose powered by a drill with some WD40 is good for polishing original bores before fitting a kit.

Mike.

I have also restored old mastercylenders before, and as stated above, if the bore is nice & clean? = no problems.

If you have(or buy) NOS, take them apart, and clean/check all parts, as the rubber has been inthere for many many years.
Also make shure to use some good (proper) rubber lube, when you put them back together.
I have some NOS parts, on the shelf, and I have taken them apart, so the rubber can "stretch" a little.

I agreed with what's been said.
The bores must be absolutely clean -and free of any pitting -If there is rust damage, then fit a new cylinder.

New seals are quite stiff. -The seals get softer as they get older.
-If you have black stuff in the fluid it's usually the 'carbon black' that is added to the rubber during compounding. This leeches out into the fluid over time, so if you have black fluid in a cylinder that has been sitting for a long time, then the seals need replacing

I have found that most of the rubber parts for classic cars (not just brakes, but suspension stuff as well), is generally of poor quality.
So try to buy good genuine stuff, such as AP Lockheed seal kits, Metalastic bushes etc. -But even buying these do not guarantee getting good parts!
-It's always worth paying the little bit extra to get the good stuff, from a quality supplier!

I'm about to send both of my M/Cs off to be re-sleeved in stainless. They are the original hexagon top style from 1960/61 so NOS are extremely rare and repros aren't available. I might have got away with just honing them but figured I'd do it once and get it right. The front wheel cylinders were both seized, but when I opened them up they were already sleeved in stainless so a quick hone and a new set of seals should sort them out nice and easy.

Tim

Tim, take extra care when sleeving the master cylinder.
There are 2 holes from the reservoir to the cylinder: the 'big' one is the by-pass port, and provides the main fluid feed. -that's no problem.
The small one (about 0.5mm dia) is the cut-off port, and the main seal passes over this in use, so you have to be very careful about how the edge is finished.
-When the cylinders were manufactured, the 'big' hole was drilled through and de-burred, but the small one was part-drilled from the reservoir side, and then pierced out from the cylinder side to ensure there was no bur.
-With the seal passing over this small hole, it's important hole it's edge is finished, -you could start chopping bits out of the edge of the seal, and then the brakes would fail

Thanks Andy, I'll make sure I double check them when I get them back. I've found a local guy to do it and he sounds fairly experienced, he said he did his apprenticeship at BMC so hopefully he knows what he's doing.

Tim

I would like to revive this 10 year old topic.

1966 Austin Cooper S (second owner).

I am faced with original clutch and master cylinders that are pitted.

I am sending them off to a rebuilder for their recommendations.
If they can be honed at a decent price I will do that.

If they must be sleeved am I better off just buying new ones?
What is the quality of the products available from Mini Spares and others?

What other factors should I consider?

Thanks in advance.

Have fitted Minispares Master Cylinders on 5 different cars in the last few years ,, never been any problem at all using Dot5 Fluid.. i go for reliability better than authenticity where Road Brakes are concerned.

I have a new minispares brake master cylinder..
I always bleed them before fitting, this one sat blead for 2 weeks as soon as I fitted it to the car it leaked ..
It now has a rebuild kit fitted and is ok so far..
D

Read this thread with interest being a practical sort of bloke.

Roger, can I suggest that before you send your master cyl's off, that you wash them out in hot soapy water first and scrub the bore. Both mine had really grotty bores that looked like they could do with replacing but they weren't leaking as I'd only taken them out to do something else. I got a piece of wood and machined it down so that when I wrapped a length of SCOTCHBRITE (pan cleaner) around it it was a good tight fit in the bore. Put it in the drill chuck for a couple of minutes and the bores came up, gleaming like new......, better than a newly honed finish.

Put them back temporarily with the old seals and they ain't leaked to this day, 4 or 5 years later. So I've still got the replacement seal sets!

Off at a bit of a tangent, but relevant.... I had considered sleeving them (myself) on the basis nothing lost, nothing gained and thought about the transfer holes. I marked the EXACT position on the outside of the can (the reservoir) so that if I did sleeve, I could go through the side of the can, into the existing hole (now a pilot) and through the new sleeve. Simple. Use the scotchbright idea to clear any fouling from the inside.

Oh, yes. Then simply tin and soft solder the holes in the sides of the can again

Long winded or wot.....

Agree with Peter here……I’ve polished a few with Scotchbrite on a stick, and what at first appears totally knackered can come up really good. So long as there’s no pitting in the seal area.
I’ve even cut a slot in a stick and wrapped fine Emery cloth around it……..not necessarily in brake part bores though…

I've used Scotchbrite too without any issue.

I do always use NOS genuine Lockheed seal kits. I dont think repro seals suffer in the same way rubber wise as everything else seems to but would rather to take the risk.

Am currently re-furbing the entire braking and clutch systems on my Mk2 Cooper (S front discs), with new seals kits.

I agree with the methods of cleaning-up the bore.
As long as there is no pitting forward of the port holes then you should be OK (as mentioned).

-If you have pitting behind the cut-off and feed-port holes, you may be OK, but you will have the risk of the cylinder leaking fluid.
And, the risk of drawing air into the cylinder...
-This has been known to happen even with 'perfect' master cylinders, the problem being the cylinder is mounted vertically... (so air getting wants to go to the 'top' of the cylinder, rather than out of the port into the reservoir).

Peter, going through the side of the 'can' is a good option, if you have a long enough drill for the small cut-off port (I guess a 'Dremel' drill with a larger shank would work).
-Like you say, the position of the holes is critical..!

- The reservoir 'can' is soldered in place, and I seem to remember somebody saying the 'de-soldered' the can and removed it completely; -another option maybe?

Sleeving the cylinder is a valid option, after all, the 'plastic' master cylinders we developed (I apprenticed at AP) had a stainless steel sleeve in them...

Glad you responded to this thread Spoons and both Andy's - above. I looked into sleeving a couple of old pitted - otherwise v-good cylinders after something I saw and learned in NZ while working there in the late 60's when they did a lot of make-do-and-mend for economic reasons.

Lengths of honed to bore size cylinder insert sleeves are regularly used in the hydraulics industry, especially the common sizes. It'd be simplicity itself to over-bore to what we used to call a 'stonking good fit' and push in a new sleeve. There's economics to consider of course but if you have access to a machine shop and a boring bar add to that a bit of confidence and experience then you're well away.
There's lots of meat to play with on the master cylinders........ But not for the feint-hearted maybe!

Sort of carrying on with this topic, has anyone experimented with “Pre-aging” the new cylinder cases ?

Too be honest, thought it had already been covered a while ago, but cant find anything….

I remember something and wondered at the time why someone would want to age something. Anyway, I think that it was something to do with staining the tin plate (?) with vinegar/acetic acid, similar to what they do to new-made 17th and 18th century antiques and the like.

Good practical thread..... But harping back a page, I looked up honed bore certified internal diameter sleeve and it's readily available

Peter Laidler wrote: ↑Fri Dec 31, 2021 4:32 pm I remember something and wondered at the time why someone would want to age something. Anyway, I think that it was something to do with staining the tin plate (?) with vinegar/acetic acid, similar to what they do to new-made 17th and 18th century antiques and the like.

Good practical thread..... But harping back a page, I looked up honed bore certified internal diameter sleeve and it's readily available

Thanks Pete, its just the new cylinder bodies are such a different finish they stand out, apprentley they cant use the old finsh anymore as its classed as Carcinogenic

Just a thought on master cylinders from my project thread.

viewtopic.php?f=6&t=33430&start=80

D