Hi,
Has anyone had any issues with seal kits for master cylinders or new master cylinders them selves?
When I had my servo issues I changed the brake master cylinder seals as they were probably +20 years old. The bore was excellent and seals fitted correctly, assembled with fluid.
The unit was tested as far as possible on the bench, pushing in the rod and feeling for a build up of pressure on the outlet port, so all good.
When fitted I found that during the bleeding process the piston would not return, but stick in the bore, this happened several times. So the MC was removed and I then fitted a brand new master cylinder that I had, as I had started to lose faith in the seal kits. I assumed that the main seal was too big. I also had an issue with a clutch slave cylinder kit, where the supplied end seal in the kit was just too small.
Fast forward 6 to 8 months and the new master cylinder is leaking via the piston seal. Note it was a Girling MS bought from one of the usual suspects and the brake fluid used was Castrol Perfomance React DOT4
As you say probably chinese quality. However, are you sure it is Girling because they haven’t existing for many years now as far as I know?
I bought a TRW brake Master cylinder for my +2 from SJS some 5+ years ago and it has been fine so far.
Hi, I had exactly this with the clutch master cylinder, bore in excellent condition, new seal kit and the piston wouldn’t return, tried another seal kit from different supplier not much better so fitted NOS original master cylinder and all perfect.
If there is a recommendation for decent deal kits I’ll buy another to rebuild my original master
So moving on with this I’ve done a couple of things…
i) Ordered a new MC (so now I have 3 in total, the original with sticking piston, the one on the car and this new one).
ii) Ordered 4 sets of seals from different suppliers.
So when I re-sealed my original MC, I kept all the old seals and small spring washers just for refrence, even though after 20 years they looked to be perfect.
So the first set of replacement seals rocked up today, the package having the old Girling seal kit number of SP2102. Well I didn’t even need the digital calipers to see the new seal was “much” bigger then the one I had removed. When I say “much” it was very noticable. Yes I know that the rubber will deform in the bore, but I wonder by how much.
Still waiting for the other kits to arrive, one of which is really really old and still in the original Girling box. Not sure I will use it, depends on how the rubber “feels”. Watch this space.
And lastly, anyone else keep their old seals for reference? would be happy to share dimensions etc.
It might be of help to use Castrol red Rubber grease. Worked fine with my clutch and brake master /slave units.
The car runs dot5 silicone on clutch system and dot3 RR363 on brake system. When the brake system will be rebuilt, it will be changed to dot5 as well
The grease is designed to be friendly with rubber. I sparingly used it in the bore (so it will not hang off in the passage drillings) And it went on the piston seals and piston. And a big dollop behind the piston, where rod and cap sits. (as you already did) Don’t forget the rod itself, both sides of the cap.
Sounds like you’ve taken all the right steps, Mark. It’s always tricky with old MCs and aftermarket seals—I’ve seen big size differences too, even in kits that are supposed to match. Keeping the old seals for comparison is definitely smart. I’d be interested in the dimensions once you’ve measured them—could help others down the line!
I have just had the same issue. Ended up rebuilding the MC with the service kit but had to re-use the old main seal for the time being.
I got my service kit from Susan Miller, as I do almost all my parts. This winter I have had problems with not only the MC seal but also Lotocones and wheel bearings. I do not blame Susan. I just feel the Chinese have a lot to answer for in their inaccuracy and inability to reproduce parts correctly. Probably better off going to Indonesia or India for repro parts!
Hi,
Absolutley bob on Tim. I know the seals SM sells are from a UK supplier as I checked them out from the packaging, the caviat being where are the the actual bits and bobs made?