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Clutch master cylinder

Posted: Mon Jul 15, 2019 8:46 pm
by Old and Slow
From the picture below, I'd say I need to refurbish the master cylinder (already bought the kit, so that's handy)..
I need to buy a flare nut spanner to remove the output pipe, does anyone know what size it is? Halfords only supply metric though. Tomorrow I'll see if I can get the master cylinder out complete with the pipe as far as the chassis plate. Fingers crossed!
Clutch_leak.jpg
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Clutch master cylinder

Posted: Mon Jul 15, 2019 9:09 pm
by Oldconn
Won't an ordinary flat open spanner do it? It shouldn't be too tight for that unless someone has butchered it.

Clutch master cylinder

Posted: Mon Jul 15, 2019 9:49 pm
by philhoward
It’ll be either 7/16” or 3/8” at a guess.

If you’re struggling to find an imperial one, crows foot spanners are available in imperial sizes and become more useful that you will ever know..

Clutch master cylinder

Posted: Mon Jul 15, 2019 10:24 pm
by Old and Slow
Phil,
Thanks for the suggestion to use a crows foot.
The open-ended spanner is already starting to round off the flats, even after soaking with Plus Gas. The problem (I think) is dissimilar metals causing an electrolytic weld.
Must get it sorted before Silverstone!!

Clutch master cylinder

Posted: Tue Jul 16, 2019 8:35 am
by David Tew
I've recently replaced some of the brake pipes and found an 11mm flare nut spanner fitted perfectly. A normal spanner will soon round off the flats, as you've found. :wink:
Flare nut spanner.jpg
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Clutch master cylinder

Posted: Tue Jul 16, 2019 12:14 pm
by Roger Pennington
11mm is very close to 7/16 AF (table here for example). It's always worth keeping an eye open at autojumbles etc, as imperial tools seem to be becoming less common these days.

Clutch master cylinder

Posted: Tue Jul 16, 2019 2:20 pm
by Old and Slow
Thanks for all the encouragement, greatly appreciated.
I disconnected the pipe at the chassis and eventually got the MS and pipe out in one piece - the biggest problem was removing the split pin from the clevis pin at the clutch pedal-cylinder plunger joint - it must have been hammered in. I'll be fitting a slimmer split pin. It had to come out to move the pedal up and get to the nuts holding the MS in.
The fluid had turned black so I knew something needed doing.
I've mic'ed up the flare nut - it is 7/16 AF so an 11 mm spanner will do the job, although I don't really need it as I can get it all back with the pipe still attached.
The piston seal was so worn that the piston assembly almost fell out, which was nice, made refurbishing easier. The new seal is very tight (and leak-proof, we hope) going back in.

Clutch master cylinder

Posted: Tue Jul 16, 2019 4:00 pm
by scimjim
I fit locking “terry pins” to pedal clevis pins.

This type
3DCE5193-220C-4DAC-AB68-FCAC468FF19D.jpeg
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Clutch master cylinder

Posted: Tue Jul 16, 2019 5:01 pm
by philhoward
I’ve got a box of R clips - I’m not as posh as Jim :mrgreen:

Clutch master cylinder

Posted: Thu Jul 18, 2019 9:33 pm
by Old and Slow
I have a collection of split pins donated by an ex-RAE engineer, about a dozen different sizes, so problem sorted. Thanks for the suggestions though.
Everything went back together easily, clutch works just as it should, even had time to vacuum the interior ready for Silverstone.
I fitted the clutch lever shroud as supplied by Oaksey - it was as hard as a hard thing, so checking on youtube I found that wintergreen oil is a plasticiser; a 100ml bottle of essential oil from amazon diluted about 5:1 with Olivio and soaked the shroud for a couple of days and it became flexible again, so fitted fairly easily, and now the underneath of the car smells "clean" ! :D

Clutch master cylinder

Posted: Sat Jul 20, 2019 11:23 am
by chrisgallacher
You treat your Sabre Six to Olivio and essential oils? :shock:

Maybe that's where I'm going wrong.

Clutch master cylinder

Posted: Wed Jul 24, 2019 2:34 pm
by Old and Slow
Hi Chris,
After massaging in the oil you need "healing hands" to lay on, as well!
A serious question: now that everything is working again, I might try to reduce the clutch pedal travel and I was wondering about replacing the 0.7" master cylinder with a 1" dia. one. Rimmer Bros. sell a MkIII 88 Landie Girling MS for around £10 (part no. STC500100P), and it looks like a straight swap (assuming the O/D is the same?).
Double the csa means half the travel, but twice the force needed to depress the pedal.
Has anyone any comments on doing this?

Clutch master cylinder

Posted: Wed Jul 24, 2019 4:11 pm
by philhoward
I’d only change by one size - if yours is currently 0.7”, go to either an 0.75” or 0.875” at most. Travel will reduce but pressure required will naturally increase proportionally. Don’t forget it’s a square law..