Emulsified/Melted Master Cylinder Rubber Plunger Seal

[Colin]

Hi Chaps;

Since body-on chassis renewal and fitting out completed, I've enjoyed running the Herald out.

I have been checking levels religiously everytime out.

I reversed out of the garage the other day:- no footbrake! Fluid down brake pedal.

OK . . . Master Cylinder seals have gone (less than 7 years old). Strange.

Master cylinder off. Internal gubbins out. Horror.

Part No.1 in your attached diagram . . . had 'melted'/emulsified - call it what you will, but a very sticky mess (it's the black slug you can see bottom left of the pic).

Now, I have used silicone brake (and Clutch) fluid for years (more than the 7 mentioned above). 

And not that it happens very often, but when cylinder internals fail (whether wheel or Master) and I obtain repair kits to refurbish, I remove the old rubbers but they have never looked (or felt) in anyway shape or form like the very sticky black mess that shows in the photo. 

It was very much the consistency of very thick marmite! I smeared it off, rather than removed it.

Is this a result of having previously used a cheap overseas produced (Indian??) rubber repair kit?

Because I have two more repair sets which state they are manufactured in India, or a couple of MoProd sets (no idea where they are procured from). I'm leaning toward using the MoProd set on rebuild, but have no evidence this will be better than Indian produce.

Moreover, puzzlingly, I didn't think anything reacted with silicone like this . . . ??? 

It took me forever to de-scuzz the plunger and internals - particularly where this seal sat and at the point within the cylinder itself where it located - nearly bunged the hole up, it was so 'liquid'!

Loads of Meths used for cleaning . . .

Any ideas, folks?? I'm puzzled.

I'm not going to stop using the silicone fluid, though.

Best, Colin

 

[johny]

I take it as you would expect all the seals (1, 8 and 13) had melted because the reservoir sealing seal 1 on its own would give brake fail but not fluid down the pedal? Its really worrying and all I can suggest is that you 'programme' seal changes say every 5 years or sooner (not a bad idea for all of us actually) because theres no way of knowing if the seals youve used are deteriorating....

[Colin]

Johny - it was actually only seal 1 that had "melted".

However, now 2 days have passed, I need help putting it all back together!! I have new 1, 3 & 8 seals - just can't remember how they were fitted and the manual exploded diagrams and Girling's own instructions are hard to figure (to me).

ALSO:- I don't get the spring retainer leaf. I lifted it to remove the spring assembly, but don't actually see that if pushed in again for reassembly, that it does anything! It's not fixing or holding anything . .  🤪

[GFL]

YouTube to the rescue😉

 

[johny]

Looks like yours doesnt use seal 13 (something Ive seen before). Then in the photo seal 8 needs to be pushed further along so its against the main shoulder of the piston and of course the right way round, which I think it is.

The spring and its holder allows the piston assembly to keep moving under pedal action to push fluid to the brakes after the front part with seal 1 has blocked of the fluid return hole to the reservoir. Then when the pedal is released the spring pushes the piston back keeping it in contact with the operating rod and pulling fluid back from the brakes so they can release.

Video a great idea as you HAVE to get this right. A lot of people just get a new complete master cylinder for this safety critical system🤔 

[Colin]

Johny:- Thanks! I have made life easier for myself by enlarging Girling instructions. 

Yes, washer should have been back against the plunger;

I now see what the spring retainer leaf does and how it fixes! Two main queries and memories re-edtablished!!

Her's another pic for confirmation. I hope I have washer no.1 the right way round and my plunger is fig 6 type A. 

So question is (more large-scale reading for me) is where does the other remaining washer (13) go & how?!?

C.

[Colin]

So here's where I'm at:- spring and plunger combo together, secured by 'leaf' push in.

Plunger washer correcty orientated and whole unit inserted into cylinder bore. 

Left with rubber washer 13 which seem surplus?? 

[johny]

yes, as said, some (earlier?) master cylinders dont use seal 13 so its not required but comes in the kit just in case you have a version that does need it.

You can test your unit now by blowing in the outlet pipe hole so air should come out of the reservoir until you just push in the piston. You then shouldnt be able to blow anymore and certainly nothing should escape from the piston... 

[Colin]

GFL - thank you! 

Think he was struggling as much as me.

I love the 'make sure it's the right way round' comment with no further clarification . . 😅😅🤣

Best, C.

[Colin]

Johny - duly tested and just as you say.

Thanks, All 😉

[johny]

Fingers crossed theres no more melting - god that little tiny seal makes me shiver!

[Colin]

It's absolutely frightening to think the entire (and obviously sometimes high pressured) braking system relies on a few roundels of (let's hope) decently made rubber. Quite incredible! 

Thanks for all helps and advices! 

Best, C.

PS hope I remember a bit more quickly 'how to', next time round!! 😀

[Colin]

And since cgassis work, I have religiously been checking levels. Was out previous week covering 100 miles +.

Then, no footbrake on reversing out of garage. What if that'd been on the A249/M2 headed east for home!!😱😱

[johny]

Dont Colin, you'll put off some of the more nervous of our members from getting their Triumphs out of the garage...

[Colin]

Soz! Handbrake's good . . . 😉

[johny]

That is a first😮

[Pete Lewis]

yes just after collecting the 2000 the servo decided to split its vacuum piston  but we did miss the bus on the roundabout 

Pete

[Colin]

 Blimey!

[Josef]

On 09/10/2024 at 12:09, Colin said:

I'm not going to stop using the silicone fluid, though.

Silicones in general are pretty inert, and not much use as solvents, so I’d be extremely surprised if silicone brake fluid was able to dissolve / deteriorate rubber of any sort.

[Colin]

Hi Josef,

Yes! I could not understand how that occurred!

(Quite a worry, really!).

Currently using Oké Dot 5 . . . 😉

[johny]

Out of interest Colin, were the failed seals new when the change was made to silicone ie. they had never been exposed to conventional brake fluid?

[Colin]

Johny; as far as I can remember, I think yes.

C.

[johny]

Because online, although many people dont do it and never have problems, the recommendation is to only go to silicone with new rubber throughout...

[Colin]

😃😉

[Colin]

Thanks for all advices:- Here's the follow-up.

As I have time, I thought I'd give my old Gunson Eezibleed kit a go and, not least, to avoid asking the Mrs to help me do the pedal work!

Trouble is, I can only just remember trying to use it once - 30 years or so ago and I don't think I got on with it.

But more to the point, I don't understand how I can bleed the system without the pedal being activated at some point . . . OR, am I misunderstanding the way the whole lot works? Instructions (simple enough) attached. 

Doesn't the pedal have be pushed down (as in when braking) to allow the car's reservoir fluid to travel out of and along the brakepipe? If so, how can tyre-pressurised fluid enter the brakepipe system WITHOUT the pedal being operated. Sorry to be so thick, once again!! 

All advice welcome.

Best, C.