Brake and clutch master cylinders

[richard sprint]

Have just stripped out my brake and clutch master cylinders - the gunky mix had to be seen to be believed but as the car has been off the road since 1981 I guess its a case of what should one expect.

My first thoughts being to just bite the bullet and fit new ones but as an excercise decided to first clean them up and see if such a simple mechanisim could be refurbished.

My thinking was that if the main bore was rust free then what could stop them being reused!

Thank goodness for the blast media cabinet for after an hours work on each M. cylinder they looked as good as new.

I then popped them into the ultrasonic tank for five cycles to remove the media and finally inspected the bores which were perfect. I now have a repair kit for each but wondered how one fits the new rubbers? does one remove the spring assembly to fit the main bore seal?

Richard

[512BB]

Hi Richard,

You need to disassemble the whole shooting match as there is a funny looking spring steel washer that needs to go in. Did your kits not come with exploded diagrams that show everything?

Leslie

[richard sprint]

Hi Leslie

No diagram just a bag with the rubber components - I will study closely for the steel washer - it looks a little like one of those xmas cracker puzzles....

Richard

[paddy]

Does it look like this:

http://www.mk1cortina.com/img/mastercyl.jpg

?

Paddy

[oldelanman]

Hi Richard,
Do you have a workshop manual? There are good descriptions and diagrams for both clutch and brake master cylinder dismantling and reassembly.
Regards

[collins_dan]

Make sure you put the end seal on as depicted in the diagram, so that the rubber extends past the end of the metal stem to create a seal with the end of the cylinder. It will go on very nicely the wrong way around, but will not create a seal and will allow air back into the reservoir under light brake pressure. Don't ask how I know, or how many times I had to install, uninstall, dismantle and re-install to figure that one out. The other piece of advice would be to lubricate the main seal very well prior to re-inserting the whole spring assembly back into the cylinder. It's very easy to tear off its edges as its somewhat cupped when going in. Again, don't ask how I know this and how many slightly torn seals are in the bin under my work bench. Dan

[512BB]

You sound like a real craftsman Dan. How much do you charge an hour?

[fatboyoz]

Richard,
Reassemble in exactly the same order as you pull it apart (durr). To remove the spring assembly, you will find a small metal barrel that holds the piston and spring assembly together and allows the spring assembly (with a cup seal at the end) to articulate. To separate the piston from this spring assembly, you will find a small metal tab on the side of the afore mentioned barrel. You have to lift this tab to separate. When reassembling, use red rubber grease liberally on the piston rubbers. If you reassemble with brake fluid only, the seals will bind.
Best of Luck,
Colin.

Have just stripped out my brake and clutch master cylinders - the gunky mix had to be seen to be believed but as the car has been off the road since 1981 I guess its a case of what should one expect.

My first thoughts being to just bite the bullet and fit new ones but as an excercise decided to first clean them up and see if such a simple mechanisim could be refurbished.

My thinking was that if the main bore was rust free then what could stop them being reused!

Thank goodness for the blast media cabinet for after an hours work on each M. cylinder they looked as good as new.

I then popped them into the ultrasonic tank for five cycles to remove the media and finally inspected the bores which were perfect. I now have a repair kit for each but wondered how one fits the new rubbers? does one remove the spring assembly to fit the main bore seal?

Richard

[richard sprint]

Thanks to all for info, diagram and advice - is now re assembled, I used the brake fluid as the lubricant, the cylinders have not been refitted so it would be easy to take apart for the red greas which seems like a good idea....

I tried my shop today but they mentioned it was so expensive and difficult to find they no longer stock or would know from where to buy it!

I then recalled buying an expensive pot of red grease a few years back. On checking it is a high performance extreme pressure grease with red moly for wheel bearings, CV joints - red line synthetic E.P. grease excellent water resistance - manftrd by Red line synthetic oil company in California!

I immersed a glob in some brake fluid and both fluids are uncontimanted by the other - so before using, might this be the one is the question?

Richard

[RichC]

i bought some red grease on ebay - simple enough - just type in " red grease " - not expensive .
RichC

[alan71]

Richard,
I wouldn?t use any grease that wasn?t specifically recommended as suitable for braking system.
Eg.
http://www.holden.co.uk/displayproduct. ... de=090.928

Alan.

[reb53]

To anyone else thinking of reconning their clutch master cylinder I thought I'd mention my recent experience.
I rebuilt it 2 or 3 times over the years. Buy a little kit full of bits, check the bore condition, wonder if it was OK, put it together anyway, seemed fine but never 100% sure etc. etc.
A couple of months ago, as I slowed down for a major intersection, I put my foot on the clutch and not only did it not dis-engage but it was totally solid. Couldn't move it no matter how hard I, ( frantically), pushed. This made the intersection and the subsequent 20 mile drive home quite interesting as the clutch was unusable. Amazing how much you have to concentrate and anticipate the traffic when you know you can't stop, ( not if you want to get going again).

The fault was a broken spring which had dug a sharp end into the cylinder wall and locked everything up.
When I sourced an entire, new, master cylinder for NZ$50, (GBP20), my first thought was, " why the hell did I bother messing around with rebuilds "?

My point being, this is one of those things that it's not worth saving a few quid on, in exchange for the peace of mind.

Ralph.

[rgh0]

Hi Richard
The redline synthetic moly grease is not a brake seal rubber grease - dont use it on your brake or clutch seals

cheers
Rohan