[Mgs] brake pressure failure switch '72 MGB

[David Ambrose]

You should never see brake fluid under that switch. Beneath the switch 
is a piston (Moss calls it a shuttle). There are o-rings on the piston 
which should seal it against brake fluid. You probably need to pull the 
whole thing and replace the o-rings, and the piston itself if it's 
corroded. You may need to hone the cylinder too.

Moss sells a couple of repair kits for that unit. I have the o-rings and 
they work fine. I don't know whether the umbrella seals are worth the 
extra money, but if the o-rings depend on a swelling agent to seal, the 
umbrella seals would make sense.

Cheers,
Dave Ambrose


On 10/10/2014 10:01 AM, sdesalvo at frontiernet.net wrote:
> I cannot stop brake fluid (silicone) from leaking out the top of the pressure failure switch. The fluid leaks into the cavity where the electrical pigtail connects to the wiring harness. I replaced the switch and it still leaks. Any help would be appreciated.
> Thanks in advance,
> Sam
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