Overhauling brake master cylinder

Do NOT use ordinary grease, or anything petroleum based - it will rot the rubber seals. If rubber grease is not available you can use a bit of brake fluid to lubricate it.

No, you need "rubber grease", the combination of normal grease, rubber and brake fluid isn't a good one and will lead to the seals perishing, so get some "rubber grease". You should be able to get it from a motor factors.

To reinforce EMB - do NOT use ordinary grease. Rubber grease is readily available from any auto parts supplier, although you may have trouble finding the small quantity you need. Many brake cylinder seal kits include some. If you can't find any, use brake fluid. Before you start on the job, make sure your work surface and hands are clean and free from dust and particularly any trace of oil or grease. If you need to clean up the cylinder, piston etc that you are re-using, use either brake cleaning fluid sold for the purpose or methylated spirits. The rubber seals used in brakes are rapidly damaged by even slight traces of anything hydrocarbon based, such as petrol, oil or grease, and poor cleanliness in overhauling these parts is one of the frequent causes of rapid failure. Not quite as bad, but still bad is dust. Any traces of roughness on the inside of the cylinder due to rust or corrosion will also cause eventual failure, and if it cannot be polished off without removing significant amounts of metal, the cylinder should be scrapped or sleeved (a professional job) JD

Thanks to everyone who replied, I'll get the proper stuff for the job. I just wondered if the 30 year old manual was still valid given that I thought they stopped using seals that were vulnerable to mineral oil in brakes years ago, from a quick Google it seems not.

Greg

We used to have a good stock of red rubber grease (aka brake grease) but when we went to re-stock the new stuff was labelled "Do't not use on rubber components"! As yet I'venot found a replacement supplier, as that suupler could not promise it would be ok.

Lucas/TRM wheel cylinder kits still come with a little tube.

Richard

There are probably a few cars that do use mineral oil for their brake fluid

- I think hydraulic suspension Citroens do for example, and there may be others, but in general, as you say "it seems not". While I am sure it is possible to make a satisfactory system using mineral oils and synthetic seals, there is probably little pressure to do so - why change unless there is a strong reason to do so, particularly with the probability of mistakes in fluid being made with a critical safety system. Citroen probably got away with their change (in 1967 from memory) because it was not just the brake hydraulic system - the same system runs brakes, power steering suspension and (some models) gearbox, so there was less likelihood of their fluid being confused with brake fluid. JD

On or around Fri, 20 Oct 2006 08:44:18 +1000, JD enlightened us thusly:

All of which is undoubtedly true and is why, provided new ones are available for less than an arm and a leg (which is the case with LR ones, i.e. they're available), I replace them rather than overhauling 'em.

Apparently Castrol do one, at least these people list it:

I'll have a phone around locally this afternoon as I hope to get the cylinder and servo overhauled this weekend.

By the way Richard, is there a problem getting the vacuum fitting and throttle spring as I haven't received them yet?

Greg

Castrol - Red Rubber Grease. 3rd product down on the link below.

£5.25 retail inc VAT for a 500gm pot.

The vacuum fitting is here, the spring is out of stock - I'll send the fitting.

Richard

Indeed - I'll see if they have a wholesaler locally.

Cheers for that.

Richard

Thanks Richard. Greg

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Lockheed (are they still around?) did a similar thing which they called Rubberlube.

You should also be aware that there is another brake grease around which is not suitable for this application. It used to be white and was a high temperature grease used on the sliding surfaces at the ends of brake shoes, adjuster mechanisms etc.. An example of this is Castrol PH grease (but it may no longer be available).

As an aside, Castrol's is another website where the last thing that they seem to want you to see is a simple list of their products. Do they want to sell anything? EMB must be congratulated for finding the page that he did!

On or around Fri, 20 Oct 2006 17:45:30 +1000, JD enlightened us thusly:

some do. LHM = Liquide Hydrolique Minerale. however, some use LHS, which is Synthetique.

some of the Rolls-Royce cars have a power braking system using LHM as well, AIUI.

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I'll second that - wholesalers are particularly bad a telling you what they actually sell - Silverline Tools being a notable exception.

Richard

Until the VW takeover they used Citroen systems, practically straight out of the box. They flid will indeed destroy "normal" seals in minutes - and vice versa.

Richard

I got some Rubber Grease from my local Motor Factors, they ordered it for me when I rebuilt the brake system on my military truck, it is Lockheed rubber grease in a 500ml tin will last me a life time and some more, if any one wants some let me know and I might be able to post it in a pot of some description for some beer tokens if any one is interested. Good stuff if you get it on your fingers as you will its a vivid red and looks like you have cut yourself really bad, good for a joke on the wife ;-)

Rich To reply remove " spam "

I just got some from my local auto-factors, it's in little sachets about the size of a ketchup sachet which I think will be just right for a single job, better than having to keep a tub spotlessly clean I would think.

If you're interested Richard it's Delph Rubberlube LPK102T from Delphi Lockheed Automotive Ltd Warwick England.

Greg

Ditto some Jaguars too.