** ON TO THE NEXT BIT ** Nose to Tail - 1972 Spitfire MkIV restoration upgrades!!

[Pete Lewis]

youre lucky they have fitted all this time most replacements wont stay in place

so concrete ones have some advantage  

ts not unusual to find they have been cut to fit over the clevis/pushrod  without disaasembly

Pete

[Badwolf]

Thanks Pete. Finally got the b*gger off.

This is a salutary warning to everyone. When you strip something down to replace/refurb, don't believe that what you see is correct....check the book. When I refurbed the master cylinders a couple of years ago, I assumed that the linkage etc was correct. STUPID BOY!!! The clue was in Pete's phrase fit over the clevis pin...!! What clevis pin, I have an overlong bolt and a locknut. No wonder I had trouble getting the rubber boot off, I am amazed that I managed to get in on and have the pedal move. In my defense, I didn't refit the cylinder after the original work was done, now 30ish years ago, but like the gear stick linkage that I serviced (correctly, by the book) some time ago, this was done without checking the manual and the nut and bolt in the clutch cyl linkage probably just have just came out of the bucket of unlabeled parts. There are several threads on the forum about how not the do jobs but I seriously wonder how many other bits and pieces on my car have been put together incorrectly by the pro mechanic who did the work, 'from memory'.

[Pete Lewis]

memory is a wonderful thing   ....if only i could remember 

hope the bolt had a shank or the threads wear the holes even more than the clevis

it does a lot of work in an un oiled non maintained hidden place ,

 pedal pivots are another ignored  Oil  Can  zone 

so for the memory  Oil anything that  MOVES 

Pete

[Badwolf]

So, had a look at the bolt that I took off and the wonderful news for the day is that it's a standard threaded bolt, no shank.  I have dug out the original tin of bolts in the hope that the clevis pin just might possibly be in with all the other spares. Not holding out much hope so the job will probably now be on hold until the replacement arrives. 

[Pete Lewis]

 you need a shank !!!   ive drilled a good few out to 3/8 10mm to reclaim worn holes 

Pete

[Badwolf]

It has been an interesting experience sorting out the clutch leak up to now. A closer inspection of the piston assembly before dis-assembly shows not only do I not have a clevis pins but a nut and bolt method of assembly, but I also have this handy piston extension plate (!!??)

which is not shown on any of the parts lists or manuals.  Any thoughts anyone. This plate is also held on with a thundering great nut and bolt. 

I have also found interesting 'floaters' in the DOT5 slicone clutch fluid

.. which is a little worrying. I have yet to strip down the piston assembly, but I think that I have found out why the master cylinder may be leaking.

 

[Colin Lindsay]

When you go to reassemble it all again, check the pedal travel against the cylinder; I suspect that's a replacement master cylinder (if not just an incorrect push rod)which has had a push rod that it soo short; hence the extension. I think you may be able to get longer push rods, in varying lengths, to suit the travel you need.

I'll go off for a quick search and report back.

[Badwolf]

Colin - I do have a spare somewhere. I feel a search in the spares boxes coming on. It will be interesting to compare lengths. As mentioned, I didn't fit this originally, just put new rubbers in it a couple of years ago.

[Mathew]

I have found replacement master cylinders with push rods shorter than standard. Ok if your old one is ok and you can swap but if not where can you get a replacement?

[Pete Lewis]

https://www.merlinmotorsport.co.uk/s/brake-clutch-parts/master-slave-cylinders/page:2

here you can get nice clevis forks and cut to length pushrods  etc  .....  play for hours 

Pete

[Badwolf]

I have finally had a chance to strip down the master cylinder.  Everything appears quite normal except for a worrying black sludge that was coating some of the parts. This might be be remains of red rubber grease or, more worrying, it could be the remains of the seals which may have reacted to the silicone brake fluid. Any thoughts anyone?

Also here is a photo of the parts after cleaning...

..as you can see the overall length of the push rod is approx. 75mm long (65mm to the hole centre), without the extension piece. Does anyone know what is the normal length for a MkIV Spitfire? As expected, the spares that I have cannot be found at the moment. Typical!!!

 

EDIT: Found it. A push rod which is 90mm in overall length (80cm to hole centre). So it does look like this was a 'short rod' extended to fit. i would still like to confirm the correct length if anyone knows please>

 

[Pete Lewis]

no idea but it needs to be the right length to get the pedal against its stop and have some rattle free play

between rod and piston cup or the fluid will not recuperate properly 

as for black ...the only black thing in there is the seals ( can we say that )  black seals matter  !!!

Pete

[Colin Lindsay]

Black sludge was always a sign of old fluid, I've no idea of what exactly it's caused by - possibly grease? - but anytime I see it I give the system a good refill.

The push rod looks to be 90, and yes the centre of the hole looks to be about 80.

 

[Badwolf]

Thanks Pete. Please see the edit. Can I assume that the two push rods are interchangeable? The measurements, ball to hole on both are pretty much the same to within a mm. I would prefer not to reuse the rod with the extension plate.

I am still a little concerned about the black crud that came out with the remains fluid. Do you get rubber slivers in brake/clutch cylinders?

Also found the old rubber boots. Still pliable just a bit scruffy. Better rubber than the modern replacement (what a surprise). What is the best thing to clean up the outside with?

[Badwolf]

Colin - Thanks. That is exactly what I have found. Looks like I have a job for this afternoon while it's raining.

I also have noticed that the little curved springy thingy was not seated properly. May not be important but just interesting.

[Colin Lindsay]

4 minutes ago, Badwolf said:

Also found the old rubber boots. Still pliable just a bit scruffy. Better rubber than the modern replacement (what a surprise). What is the best thing to clean up the outside with?

Black boot polish. Any of the proprietary rubber cleaners will make them look wet and shiny, only until they dry, when they go grey or white again. As long as they're supple and not cracked, boot polish gives a nice black colour. You can also use it on tyre sidewalls to freshen up the tyres.

[RogerH]

1 hour ago, Badwolf said:

 This might be be remains of red rubber grease or, more worrying, it could be the remains of the seals which may have reacted to the silicone brake fluid. Any thoughts anyone?

 

Silicone brake fluid should not (does not) affect the rubber seals. Even if the seals were used with DOT4 before hand.

If you flush your master cylinder out and put new DOT 4 fluid in the fluid will turn black pretty quickly. I thing SBF will do the same.  I don't think it is the seals. Possibly an effect of the seals polishing the Ali bore.

 

Roger

[Badwolf]

RogerH - Thanks for the advice Roger. If the fluid had just been a grey colour I wouldn't have been worried but it was the fact that the sediment looked like bits of rubber that made me think that the seals might be decomposing and breaking up. As the brake cylinder was done at the same time as the clutch, paranoia set in. However....I have just remembered that my old friends the professional garage may have had a hand in this as after refurbing the clutch cylinder, I found that the clutch had seized after being stood for several years and they freed it off!! Wonder exactly what they topped up the fluid with even though I supplied them with a bottle of dot 5.

[Pete Lewis]

both brake and clutch   are same design apart from might have  variations in bore dia  and reservior capacity 

both have the same design internals and pushrods 

if the little wavy washer was displace that would affect recouperation as it pre loads the end seal and acts as a sort of valve 

 

[Badwolf]

That might have been the cause of the fluid weeping out slowly.... I hope so, as there is no sign of any damage to the washers or the internal bore. Fingers crossed.  

[Mathew]

52 minutes ago, Pete Lewis said:

both brake and clutch   are same design apart from might have  variations in bore dia  and reservior capacity 

 

Arr the bore dia, have had fun swaping to give either harder or softer pedal pressure. Stay with standard if standard. Had to go up on the brakes with four pots! Otherwise the travel was too long.

[Badwolf]

All back together now. Waiting for a new clevis pin to replace the thumping great nut and bolt. Then the fun starts to bleed the system. It took ages to get the muck out of the cylinder bore which had worked it's way back into the reservoir. There was a congealed circle around the point where the piston rubber would have been parked. It did look very much like congealed red (but black) rubber grease. I don't remember using it previously but then.....???  This time I have just used a smear of brake fluid to lubricate. Now just the decision to make whether to struggle trying to fit the old rubber boot (which looks lovely after a quick going over with black boot polish - thanks Colin), or to slit it, fit it, and secure with a tie wrap around the top. There is also the fun getting rid of the leaked fluid out of the interior..maybe the power washer on the carpet and panel wipe on the metal. It's supposed to be nice but cold this weekend and the drive needs washing down (with the power washer not the panel wipe)

[Badwolf]

Before I go berserk and strip out the tunnel cover etc, does anyone have a clever way to bleed the clutch system. I read somewhere that it can be done from underneath but have never tried it. In the past I did it from inside. The pipework was unscrewed and capped before attempting anything else on the master cylinder so there should not be much air in the system at the moment, not that I suppose it will make any difference. I do have my wonderful brake/clutch bleeding device...Lady BW on standby.

[Mathew]

2 hours ago, Badwolf said:

Before I go berserk and strip out the tunnel cover etc, does anyone have a clever way to bleed the clutch system. I read somewhere that it can be done from underneath but have never tried it. In the past I did it from inside. The pipework was unscrewed and capped before attempting anything else on the master cylinder so there should not be much air in the system at the moment, not that I suppose it will make any difference. I do have my wonderful brake/clutch bleeding device...Lady BW on standby.

Only if you cut and plate a patch in your tunnel cover. I did mine so i can blead and top up the gearbox from inside without stripping cover off.

[Pete Lewis]

es done it from under a spitfire once with a  socket and extn and knuckle on the bleeder , quirt it  on the floor wash off with water 

still needs a muppet on the pedal  &  nip before each back stroke 

so you need rent a crowd and a jack and stand under the side youre working unless youre skinny 

one down under 

one watchng the reservoir 

one pumping 

 

simpulze   !!!

Pete