leaking brake reservoir - problem solved

[stevefoster]

There was a thread about this a fair while back. I remeber the solution being ditching the fluid level test gubbins and going for a straight forward cap.

I didn't have the problem back then but have over the last few months.

It's due to the design of the cap incorporating the naff but necessary by law, brake fluid warning level test switch.

 

After spirited driving a small amount of fluid gets past the seal. The reason for this is that the lip that acts on the seal in cut away to allow the cap and switch to be assembled. So the seal doesn't act on something round with even pressure.

 

I found that that adding a suitably sized 'O'

ring under the existing rubber ring seal in the cap completely solved the problem.

Simple but worked for me.

I thought I would share this...

 

Steve

My racing pics, 7 DIY, race prep. Updated often here

Hants (North) and Berkshire area club site

here

 

[philwaters]

Yes, but did you weight it before adding it to the car? 😬

 

Phil Waters

Zetec is in and running

[scooby dooby doo]

I'm changing to the non MOT compliant race cap - the normal cap leaked so much it destroyed the firing mechanism housing on my extinguisher 😳

 

HOOPY CYCLE WINGS CUCUMBER

[JAG]

The brake fluid reservoir cap does have a small drilling to help equalise the internal reservoir air pressure with the outside world air pressure. Under 'exuberant' driving conditions it is just possible for brake fluid to leak past the labyrinth inside the cap and escape via this air bleed hole.

 

Could this be what is happening?

 

of course without this air bleed hole the brake fluid in the reservoir wouldn't be able to flow into the master cylinder when you took your foot off the brakes - so there must be one in the 'racing' cap.

 

JAG