Pkitson Posted June 24, 2015 Report Share Posted June 24, 2015 Trying to rebuild the master cylinders i have a problem. On the piston there is a cup shaped rubber seal but also an 'O' ring on the piston. This O ring is not shown in the Moss parts list and is not supplied with the rebild kit, is it essential in which casi i shall have to make something as the original fell apart! Quote Link to post Share on other sites
Grahamgl Posted June 24, 2015 Report Share Posted June 24, 2015 Hi, You can buy boxes of O rings, make sure they are Imperial if your master cylinder is original. Graham Quote Link to post Share on other sites
Don Elliott Posted June 25, 2015 Report Share Posted June 25, 2015 One of the original pistons in one of my master cylinders had the O-ring in the groove. Since there was no new O-ring with the new seal kit, I left it out. It has never been a problem without this extra O-ring seal. The other piston in the master cylinder never had the groove for an O-ring - so I assume that at some point in the assembly of new TRs, the factory deleted the front O-ring. Quote Link to post Share on other sites
Pkitson Posted June 25, 2015 Author Report Share Posted June 25, 2015 Thats what i guessed so have put it back together with no O ring and all appears ok except for the usual bleeding job.. I do it the old fasioned way as i find the one with an auxillary tank under pressure tends to leak fluid over my nice new paintwork. Quote Link to post Share on other sites
Herald948 Posted June 25, 2015 Report Share Posted June 25, 2015 That "O" ring (along with its corresponding groove in the piston) was eliminated by Girling in the early 1960s, apparently having served no useful purpose. I've seen (but cannot locate at the moment) information regarding this from Girling. Quote Link to post Share on other sites
Pkitson Posted July 9, 2015 Author Report Share Posted July 9, 2015 Still having problems here if anybody can help please. It appears the spring in the master cylinder is not strong enough to push the piston back about half the time. The pedal returns as it has its own spring but the piston is left down the bottom of the bore. I did check the piston moved freely in the bore but of course when you add the rubber seal it is much harder. I dont think the spring is available so am i forced to buy a new master cylinder. Any thoughts please. Quote Link to post Share on other sites
billy l Posted July 10, 2015 Report Share Posted July 10, 2015 (edited) Have you assembled the cylinder dry? if so remove the piston assembly and smear brake fluid all over the seal and piston and then re-assemble, don't forget that in normal use the piston doesn't travel all the way down the cylinder. Hope this helps. Bill. Edited July 10, 2015 by billy l Quote Link to post Share on other sites
Graham Harris Posted July 10, 2015 Report Share Posted July 10, 2015 Also the wheel cylinders are pushed back by the brake shoe springs which sends the fluid back to the master cylinder . You need to bleed and adjust the whole system and it should all come together as it should. Graham Quote Link to post Share on other sites
Lord Flashart Posted July 18, 2015 Report Share Posted July 18, 2015 I use the red rubber grease on assembly to avoid the piston sticking. Paul Quote Link to post Share on other sites
Richardtr3a Posted July 20, 2015 Report Share Posted July 20, 2015 Do not buy any new cylinders. i had endless trouble until I had the original cylinder overhauled by a specialist. This cured all my problems. I wish that I had gone further and fitted a stainless steel liner. Under examination the quality of the new casting is very bad and the surface is too rough inside for such an important part of the car. Good Luck Richard & H. Quote Link to post Share on other sites
Don H. Posted July 20, 2015 Report Share Posted July 20, 2015 (edited) ...i had endless trouble until I had the original cylinder overhauled by a specialist. This cured all my problems. I wish that I had gone further and fitted a stainless steel liner... I had my original brake and clutch master cylinders and the original clutch slave cylinder re-sleeved in brass and overhauled by Apple Hydraulics here in the US. The did a good job, and I'm quite happy to have the original castings back in service where they're working flawlessly. There are two companies here in the US most known for this service -- I'm sure you have your best choices in the UK, too. Edited July 20, 2015 by Don H. Quote Link to post Share on other sites
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