Wheel Cylinder Seal

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northernboy
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Wheel Cylinder Seal

Post by northernboy »

Am just in process of refurbishing my wheel cylinder assemblies. The pistons and cylinders looked to be in reasonable condition with only a few light marks. Following Feb issue of 'Practical Classics' when they have an article on restoring clutch cylinders (same principle as brake I guess) I decided to gently hone the bores and then 'polish' up with an abrasive pad. When done bored looked bright and smooth. The pistons likewise polished up well. I fitted new seals from BM (with large taper towards the oil input/output). However, on all four cylinders when I push the piston with seal into the bore they hardly offer any resistance. (Unlike the master and frame cylinders which felt tighter and the seal was doing something).

How tight are these meant to be with new seals ?

Are there different seals available?

Piston Diameter = 20.11mm / 0.791 in / or fractions 13/16

Cylinder diameter = 20.44mm / 0.805 in or fractions 13/16

Does anyone has correct diameter size for the piston and cylinder bore please?

Thanks

Nick
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Dave Clark
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Re: Wheel Cylinder Seal

Post by Dave Clark »

With respect Nick the sizes of bore and piston are pretty irrelevant because the seal does the work, as I am sure you know anyway.

I suspect those seals are some produced for BM and not Lockheed spec.

Try fitting a piston and seal, holding a cloth over the open end of the cylinder and apply some air pressure to the inlet port and see if it moves the piston easily. If so the seal will probably be ok.
pick up phil
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Re: Wheel Cylinder Seal

Post by pick up phil »

Having cleaned up dozens nay hundreds of these for the Club spares scheme before they go for resleeving, unless its shadowing on the photo, it looks to me like they are pretty rough.

The seal is usually pretty tight when you assemble them. Have you lubricated the piston and bore with brake fluid?
I can assure you that they are tight when removing siezed pistons!! Luckily I have a magic tool!!
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A40FARINAGURU
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Re: Wheel Cylinder Seal

Post by A40FARINAGURU »

pick up phil wrote:Having cleaned up dozens nay hundreds of these for the Club spares scheme before they go for resleeving, unless its shadowing on the photo, it looks to me like they are pretty rough.

The seal is usually pretty tight when you assemble them. Have you lubricated the piston and bore with brake fluid?
I can assure you that they are tight when removing siezed pistons!! Luckily I have a magic tool!!
i's better to go for exchange re-sleeved ones from the club, you haven't got a secondary back up system if they fail other than the hand brake, ref Phil's brake fluid lube, you can buy Red brake grease for assembling, i think i'm still using a good old Lockheed one in a 1 litre pot :thumbs:

http://www.ebay.co.uk/itm/Silverhook-Re ... SwA3dYf5g3
Nick Bayliss

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northernboy
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Re: Wheel Cylinder Seal

Post by northernboy »

As the whole brake setup has been stripped and cleaned and all new pipes, I am intending on using DOT 5 silicone oil as it does not absorb moisture and is meant to last much longer. I therefore used silicone grease to lubricate everything prior to re assembly. The bore does look better than the photo but happen they are just not good enough and have worn and now the tolerances are not good enough any longer. I tried connecting my airline as Dave suggested at 110 psi and is fair wacked the piston out but when held in a vice did seem to leak some air. So if air at 110 psi leaks, hydrolic oil at presumably much higher pressures will also leak which is no good.

Absolutely correct, brakes are pretty important and not worth taking chances but just want to make sure it is the cylinders and pistons that are at fault and not the seals or something else silly before I shell out for 4 replacements - yikes !
My Fleet : Austin A35 (aka Dads funny old car), 2003 1.8 MGTF - (Dads cool car and Daily Driver), 1982 Mini Mayfair and the family Focus Hatch (aka 'The Skip')
northernboy
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Re: Wheel Cylinder Seal

Post by northernboy »

I have just found an old cylinder in my cupboard that has not been 'renovated'. I cleaned out the grunge and measured the internal diameter of the bore and it is 0.2 mm less that the ones I have renovated, this does not sound much but I tried one of my pistons with seal and it does feel a better and more confident fit.

I have come to the conclusion honing these is probably not a good idea and getting back to a half decent finish takes away too much material on a worn out part rendering then only good for re sleeving.

OK - lesson learnt - not going to mes-about - Club spares tomorrow and 4 replacements please !
My Fleet : Austin A35 (aka Dads funny old car), 2003 1.8 MGTF - (Dads cool car and Daily Driver), 1982 Mini Mayfair and the family Focus Hatch (aka 'The Skip')
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A40FARINAGURU
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Re: Wheel Cylinder Seal

Post by A40FARINAGURU »

northernboy wrote:I have just found an old cylinder in my cupboard that has not been 'renovated'. I cleaned out the grunge and measured the internal diameter of the bore and it is 0.2 mm less that the ones I have renovated, this does not sound much but I tried one of my pistons with seal and it does feel a better and more confident fit.

I have come to the conclusion honing these is probably not a good idea and getting back to a half decent finish takes away too much material on a worn out part rendering then only good for re sleeving.

OK - lesson learnt - not going to mes-about - Club spares tomorrow and 4 replacements please !
club spares also do the pistons :thumbs:
Nick Bayliss

Club's A35 (Saloon) Registrar, South Midlands Area Contact

Email, a35@austina30a35ownersclub.co.uk

Connected with A30/A35's for 63 years

A30/A35 Member A1372 (since 1981)
pick up phil
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Re: Wheel Cylinder Seal

Post by pick up phil »

The club ones come with either an original piston, or for a few quid extra you can get a new one piece one, so the adjuster will never become loose and the clicker spring spokes shouldn't snap off. They also come with new rubbers for you to assemble.

I agree with using DOT 5.1 fluid. My pickup has had it in for the last few years - still had a couple of seized wheel cylinders though and had to replace master cylinder.
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Re: Wheel Cylinder Seal

Post by Dave Clark »

DOT 5.1 should be replaced every two years according to instructions.

DOT 5 (silicone) lasts indefinitely.(Been in TMT for over 5 years)
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