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Non vented Master Cylinder cap

Posted: Sun Jul 27, 2025 9:53 pm
by TomPartridge
Hello folks,

Just about to do a disc brake conversion, but the only thing ESM didn't have was the unvented Master Cylinder cap.

Anyone know where I can get one? Anyone have one lurking in the garage they would part with??

I know you can self tap/araldite, but would prefer a better engineered solution!

Thanks in advance.

Re: Non vented Master Cylinder cap

Posted: Mon Jul 28, 2025 7:51 am
by philthehill
The only reason for fitting the unvented cap is if you want to fit a remote reservoir.

The remote reservoir is not a absolute necessary.

I have run Marina disc brakes on both my Ser2 and my Minor without the additional reservoir and have never had the need for additional brake fluid.
If the car is serviced and maintained correctly the brake fluid level will be checked on a regular basis.

Re: Non vented Master Cylinder cap

Posted: Thu Aug 28, 2025 10:18 pm
by bobtail4x4
they say "Only for use with standard spec brake fluid i.e. Dot 3 or Dot 4. (Not Silicone fluid)"

do we know why?

my newly acquired traveller has a remote and dot 5
and a leak somewhere under the car,

Re: Non vented Master Cylinder cap

Posted: Fri Aug 29, 2025 12:53 am
by svenedin
What is not for use with Silicone brake fluid? I am not sure I follow.

Silicone brake fluid is not suitable for modern ABS systems but has been used by the military for older vehicles for many decades. The reason being that vehicles that are stored but not maintained in immediate readiness cannot be found to have seized cylinders or time wasted messing about changing ordinary glycol brake fluid just to stop cylinders seizing.

I had a seized cylinder (usually at the back) many, many times before I changed to silicone brake fluid. It has never happened since. Don't believe all the nonsense you read. It's a no brainer. Bleeding is exactly the same, no more difficult except you can piddle the stuff everywhere with no fear of stripping the paint. :lol: Be aware though, silicone contamination of paint leads to severe orange peel if you try to re-paint before cleaning it off (same incidentally with shellac French polish on antiques with modern silicone spray polish). Silicone fluid should still be changed periodically though and this will happen as a matter of course because the flexible brake hoses still perish from the outside......You can also (and should) with a silicone system, protect rubber parts with silicone grease. It reduces the ageing of the rubber from oxidation.


Stephen

Re: Non vented Master Cylinder cap

Posted: Fri Aug 29, 2025 10:10 pm
by bobtail4x4
I asked ESM they say
"The hose in these kits is only suitable for DOT 4 fluid."

its a braided plastic hose on mine, the kit looks to have rubber hose,
looks like the pipe to reservoir wasnt fully tightened, found the pipe was wet,

Re: Non vented Master Cylinder cap

Posted: Wed Sep 03, 2025 4:48 pm
by MMT1968
Well, I bought my unvented master brake cylinder cap at ESM‘s.
It’s a bit hard to find in their shop catalgue.
The order code is: FBK903

Chris