Brake master cylinder won’t dismantle

[ChipChipChipper]

So I’m rebuilding the brake system on a 1970 S2 2+2 4.2

I’ve removed the master cylinder and started dismantling but I can’t get out the main piston, bearing or plastic cover.

I’ve removed the circlip and the books I have (Autobooks, Haynes & Bob Bate) say the piston should just pull out but I’ve tried everything and can’t get it to move.

So far I’ve put the piston end circlip back on so I can tap a spanner to try to pull it out. I’ve blocked the other outlets and pressured the cylinder and tapped it again. I’ve put a thick plastic pipe on the bearing and tapped it to see if will dislodge but nothing seems to have moved it at all.

I thought about leaving it but looking in the outlet hole looks like the spring might be broken so I want to check that.

I’ve read the bearing and plastic cover are no longer available so am trying not to crack either and the piston needs to be sealed so not scratching it.

Am I doing something wrong or do you know any tricks or is it just a case of strong arming it off?

Here’s a photo of the stubborn bugger (the bearing not me)



Thanks

[Mich7920]

Hi Ian,

Do you fit out the "stop pin" locate at the botton of the hole of the inlet connection ?
Look the knowledge base / serie 2 / brake

Mich

[ChipChipChipper]

Thanks Michel. Can’t find any sign of a stop pin.

In the KB for S2 brakes there’s this diagram which I presume is originally from Jaguar as it’s in all my manuals:



I can’t see a stop pin here either and it seems to conform to what I have. Is there something missing from it?

Thanks

[ChipChipChipper]

I should add I got it from the Dropbox pdf from S2 brakes link on this KB page (in case I’m on a different page to you)

http://forum.etypeuk.com/viewtopic.php?f=16&t=700

Thanks

[Mich7920]

With the bulge of the body I thought it was the servo.
Sorry I did this but didn't remember any problem.
Do you try with pressure air ? Beware your eyes.

[ChipChipChipper]

Yes tried with pressure and tapping a spanner on the piston at tHe same time. I had the compressor up to 10bar with a tube held into the cylinder by hand internal cylinder pressure wouldn’t have been 10.

Think I’ll fashion a tapped attachment to directly pressure the cylinder and try that. Will get everything clear of the piston including eyes!

[Mich7920]

I just advise you to have a drink and a good night before doing the job...
You'll find the solution more quietly
Mich

[mgcjag]

Hi Ian...think i remember mine was stuck.....dont do anything drastic....use combination of tap it in a touch then air to push out....just keep on....in/out.....Steve

[ChipChipChipper]

I’ve had two nights sleep on it. This is the third day of trying.

Just tried a ring spanner on the piston then cabletie and circlip and tapped that. Didn’t work and has marked the piston a bit so won’t try that again.

So the only thing left is to try the drink.

Cheers chaps

[angelw]

Ian Wrote:

Just tried a ring spanner on the piston then cabletie and circlip and tapped that. Didn’t work and has marked the piston a bit so won’t try that again.

Hello Ian,
Arrange threaded nipples to allow a high pressure grease gun; 10,000psi is what I use on stuck Brake Caliper, Master and Slave Cylinder pistons, to be connected to the port downstream of the piston and blank off all other orifices. Its way more controllable than compressed air and will shift the most difficult to move pistons without damage.

Regards,

Bill

[Mich7920]

Sure a drink ( or more ) work fine...
Perhaps gently with a inertia hammer fixed on the circlips ?
It's very annoying when we don't understand the WHY of the problem.

[abowie]

The blue/green plastic valve housing has an o ring around the outside of it to make it seal in the bore.

In an old master cylinder these go hard and make it very hard to get this piece out, especially if there is any corrosion of the bore above it. Problem is if you break the bearing you can't get them as a spare part.

You should be able to get it to move with some lubricant and either pulling on the piston or pressurising the cylinder or a combination of both.

In the past we used to get the masters resleeved and rebuilt for restorations but these days it's cheaper and easier to just buy a new master.

[Mich7920]

What are the news ?

[ChipChipChipper]

I had a drink and realised the gauge on my compressor goes to 20bar and I have a heavier hammer in my toolbox.

The result :



In truth it was a case of lubricate, tap, lubricate tap and repeat. The comments on this forum confirmed that was the way to do it and thankfully my father persisted and persisted until it came out.

Thanks all

[Mich7920]

Great !
Only with your father...

[abowie]

Good outcome. They can be very tricky to disassemble.

[Philippe-J.]

I faced the problem of pulling the piston off the master cylinder too.
I tried and "gently" tapped the cylinder with the piston end stretched in a vice. All I succeeded was to damage the surface of the piston. So I had to buy a new one.
The solution I eventually used is the following. I purchased a "half ring" with a ID just smaller than the OD of the piston and tightened it onto the piston:

Then I used a bearing puller that could hook to this half ring. Its screw pushes ontop of a square tube in which I cut two windows for the puller arms:

And hey presto the piston came off in a dream
But why didn't I find that one before I destroyed the first one ?