Brakes: What lubricant is on new Wheel Cylinders (brakes) ??? How can it be compatible with brake fluid?

[bsrosell]

Curiousity question only here (after having to take apart my "new" brake Wheel Cylinders yesterday).

They definitely are lubed with something, almost feels like Vaseline and is clear... and makes sense they need something to prevent corrosion during shipment/storage before sale and use. (mine going 6 years was just a bit long..)

But WHAT is compatible with ANY brake fluid that the eventual owner might use? DOT 3 or DOT 5.....?? (or brake fluid of ANY kind?).

I never thought about it before. You'd almost think the wheel cylinders would come with instructions to completely flush with alcohol and be "clean" immediately before mounting, and relube with the brake fluid that you'll be using...

Just curious. Would have never thought about it had I not ripped the outer seal and had to open a brand new cylinder....

[Jeffry Cassel]

I believe it is SOP to clean and lubricate the new cylinder with brake fluid. I have to admit that I have omitted this without any dire consequences. I use only Valvolene fully synthetic brake fluid. It is compatible with the cheap stuff so you could just flush it out. Neither is compatible with silicone fluid which I used to use but never ever again. Among other things it takes out brake lite switches, and I sorta feel better with brake lites. There may be a few drivers who are paying attention.

[r1lark]

I use brake cylinder assembly lube, Raybestos BAF-12: https://www.summitracing.com/parts/agb-baf12

One bottle lasts a long time.

[StudeRich]

You don't hear THAT everyday! Never heard of anyone having a problem using DOT 5 Silicone Fluid that was not easily fixed with a Mechanical Stoplight Switch!

Sure there are those with "Loose" systems that developed slow leaks, but that also can be easily corrected.
Also, never heard of anyone using Synthetic Brake Fluid! I don't see how that could be any different than Silicone. Must be DOT 4A

[r1lark]

I believe it is SOP to clean and lubricate the new cylinder with brake fluid. I have to admit that I have omitted this without any dire consequences. I use only Valvolene fully synthetic brake fluid. It is compatible with the cheap stuff so you could just flush it out. Neither is compatible with silicone fluid which I used to use but never ever again. Among other things it takes out brake lite switches, and I sorta feel better with brake lites. There may be a few drivers who are paying attention.

I too have started using the Valvoline synthetic brake fluid, at least in the cars that I don't have DOT 5 in. Honestly, as far as brake light switches, I've had as much or more failures on cars with 'regular' brake fluid in them than I have had in the cars with the DOT 5 fluid. I wonder if, like a lot of other things, cheap manufacturing processes and/or materials are impacting the brake light switches longevity also.

[41 Frank]

Never use any petroleum based products to clean or lube wheel cylinders! When in doubt what to use pre-lube with the type of brake
fluid you will be using.

[bsrosell]

Never use any petroleum based products to clean or lube wheel cylinders! When in doubt what to use pre-lube with the type of brake
fluid you will be using.

That is exactly what I would "spec" (I'm a mech.engineer); but SOMETHING was on the wheel cylinders to 'protect' the bore, and I recall this on other ones (rear drums on my 90's cars)... and never thought about it before; must be something like the "assembly lube" R1Lark mentions; which means, perhaps?, there IS something out there determined to be compatible/absorbed by without issue, into ANY kind of brake fluid the customer is using?
They don't know what you'll use, so can't be brake fluid (unless until recently all cylinder manufacturers 'correctly' assumed DOT3 for everyone?
Does make you think in the future (if I ever do another set of drum brakes; '53 Buick hopefully yet someday!), that you should disassemble and flush with brake cleaner (NOT the rubber parts!!!) and all of it in alcohol, and then get YOUR fluid back in them and assemble right away... (I sure appreciate having discs on my 2000 era Toyotas and Chrysler!)
Thanks for the thoughts guys. Just made me think seeing something ooze out of a new cylinder.... :-)

[55s]

I purchased and used Red Rubber Grease. Happy so far. It was highly recommended by a few MG owners. (Not sure if the links will still work)

"The purpose, features and uses of red rubber grease.

Why do we need Red Rubber Grease?

Rubber without lubrication dries out, hardens, crackles and breaks. If affected by gasoline or if lubricated with petroleum-based grease, it swells, loses its shape and does not do the work as intended. When in contact with moving parts, it wears out from friction (an o-ring against a brake caliper or cylinder piston, a dust boot against a clutch plunger) and also may rupture. And, finally, during assembly, it is hard to push a piece of dry rubber into a casing and even more so to slide one rubber part onto another.
To help in all of the above situations red grease was designed, Castrol RRG being one of the best known brands. Being a vegetable oil based lubricant this grease does not harm rubber and can be used for its protection, lubrication and preservation. It can also be a great help during assembly of units containing parts made of natural or synthetic rubber and even plastic (installing bushings, for example).
Because of a unique combination of two of its qualities: natural rubber compatibility and brake fluid compatibility the main use of Red Rubber Grease is in hydraulic brake/clutch applications.
What is the main purpose of RRG?

Preserving natural rubber parts, lubricating rubber to rubber or rubber to metal contacts, helping in assembly of units containing rubber parts.
Red rubber grease uses.

Because of the qualities mentioned above Red Rubber Grease it is ideal for use in hydraulic systems, namely, hydraulic brakes and clutches or shock absorbers, pneumatic systems containing rubber parts (o-ring, seals). For this reason a sachet of the red grease comes as a standard part of quality brake/clutch and motorcycle fork oil seal and dust seal repair kits.
In contrast to regular automotive lubricants that are petroleum-based, red rubber grease is vegetable oil based (red dye is added for identification purposes) - this is the reason why it's "rubber friendly". Being that, RRG can be used where ever natural rubber is used in the car (see some applications mentioned on this site.)
Here is a comprehensive list of RRG properties:

• Fully compatible with natural and synthetic rubbers
• Compatible with brake fluids and some hydraulic oils.
  
• Rust inhibitor (protects from oxidation and rust).
  
• RRG is water resistant.
• Hight temperarure. The grease can be used in applications with temperatures up to 210-230F. It will not melt and will not contaminate brake pads.
• Petrol resistant. Although it will get contaminated in contact with gasoline, but still it will protect rubber parts from it.
• High chemical and structural(mechanical) stability.
• High resistance against water washing (will stay on after a rain, or car wash).
• Has high wear protecting quality.

In other words, RRG can be used for lubrication where there is rubber and there is no gasoline: o-rings, non-petroleum oil and dust seals, dust boots, bushings.
Read the technical specs and MSDS of Castrol red rubber grease and also of RRG from such manufacturers as Millers Oils and Fuchs on our Tech info page.
Learn how to use rubber grease when rebulding brake calipers.
Learn how to use rubber grease when rebulding clutch master cylinder"

[wittsend]

Another vote for Red Rubber Grease..., say-ith I, an owner of a Sunbeam Tiger. If you are looking for something less generic than they sell on Ebay, try Moss Motors. Last time I looked they sold the Girling in the soft packet.

[bsrosell]

Thanks 55s and wittsend! Very interesting, and may come in handy if I DO ever get to my Dad's '53 Buick convertible (lots of work left on my Hawk!!). Makes sense. Wonder if that is what the manufacturers of these cylinders use though; certainly doesn't APPEAR red; BUT, maybe it is simply vegetable oil? Same principle? (no petroleum, yet avoids dry rubber and protects against dry machined surface rusting?). I wonder. Again, curiosity..... (but I'll be cleaning and relubing any new wheel cylinder I ever install on any car, from now on), even though they likely know what they are doing and have something compatible with brake fluids (you'd hope!?).