Brake cylinder fur

[stag36587]

I was a bit disturbed to see some fur round my offside rear brake cylinder connection (same consistency as the fur you sometimes see on battery terminals). Does that indicate a problem like a leak perhaps or am
I worrying about nothing?[frame][/frame]

[dalebrignall]

is that a chemical reaction with dissimilar metals

[graham1957]

i think i would dismantle and have a good look, it seems something is attacking the alloy cylinder!and check the other side as well

[Pikey]

I would say it's perfectly normal and nothing to worry about,, it's as dale says above, it's a process called electrolysis, chemical reaction between the aluminium cylinder the copper washers and the brass banjo. The aluminium is just the weaker metal between the three so it corrodes slightly.

[philthehill]

Whilst electrolysis corrosion is normal I would still strip it and see the full extent of the corrosion as it may be worse than first thought.
Looking at the attached picture there does not seem to be a copper washer (Pt No: 233220A (MOSS)) between the bleed nipple union banjo (Pt No: 27H7189 (MOSS)) and the brake cylinder. There should be one either side of the bleed nipple union banjo. The outer washer (Pt No: 3H550 (MOSS)) is in place.

[graham1957]

yes i was unsure about weather a copper washer fitted, maybe thats why there is more than i would expect corrosion wise!!

[stag36587]

Thanks guys I will check whether the washer is there when I get a moment

[RobThomas]

I had the same happen on a Mercedes SL. The hydraulic system for the suspension used an alloy washer between steel components and this rotted out at 35000 miles. The difference on the Merc is that the suspension then drops about 6 inches until the front wheels tuck up inside the front arches enough to prevent the steering from being turned. If the system fails whilst the steering wheel is not central then the tyres will rip the front wings off. No, really!

It the case of the Morris, what grease might be suitable to protect this area? Red rubber grease might be safe to use but I'm not sure how well it keeps moisture away. Lthium waterpump grease might also suit but I'm not sure how it affects rubber components. Lanolin???

Any experts on here?

[bmcecosse]

A wipe over with Waxoyl?

[chickenjohn]

I would be more worried about corrosion on the INSIDE of the wheel cylinder! Removal of the outer piston and application of red rubber grease will give longer life to the cylinders (and red rubber grease does not attack rubber like other greases and oils do).

[RobThomas]

Well, the Phosporic acid in Waxoyl might help remove the oxidised ali corrosion but the white spirits used in the production of Waxoyl is unfriendly to rubber, especially EPDM-based O-rings. Since the rubber gaiter (and rubber brake internal seals!) is so important in keeping the brakes functioning it would be best to avoid anything that perishes it. A flick through the internet seems to support Red Rubber Grease as the better candidate.
An example for £2.08...
http://www.ebay.co.uk/itm/18g-Castrol-R ... xyu~lSTrTO

[bmcecosse]

I'm not aware of phosphoric acid in waxoyl - and it is regularly sprayed all over and into the cavities of older cars without seemingly doing any great harm..... So it certainly wouldn't worry me to use it there. I do use red rubber grease - but only normally inside the cylinders. I suggest if that union is disturbed now - it will be back to the beginning again with the brake bleeding nightmare!

[stag36587]

I suggest if that union is disturbed now - it will be back to the beginning again with the brake bleeding nightmare![/quote]

Tell me about it! A wee dram will be needed beforehand or afterwards.... "Wee" will be directly related to the size of the bleed nightmare

[philthehill]

Personally I would rather have brake bleeding problems than having an accident as a result of the failure to fully examine the extent of the corrosion.
It would be complete folly not to strip and examine.

[RobThomas]

https://en.wikipedia.org/wiki/Waxoyl

[les]

I think waxoyl is great stuff but apparently it should be wiped of rubber hoses etc.

[stag36587]

I had a quick check last night. Corrosion was less than it first appears and the copper washer is in place as it should be. The wheel cylinder was installed less than a year ago. I'll have a further check at the weekend.

[bmcecosse]

Just scrub it clean with a toothbrush and apply a wipe of the protection grease (or just a spot of brake fluid) of your choice... Clean the toothbrush well of course before returning it to the bathroom cupboard.......

[stag36587]

I thought I might pass the fur off as new-fangled organic toothpaste