Brake Fluid Loss at Track Days

[Baby Bucket]

Hi,

 

Sorry for the obscure title, but the problem is this:

 

Went to a track day at Donington on Friday, had a fab day but at the end of a session, noticed that the Brake Fluid was weeping out of the top of the reservoir attached to the master cylinder. After a while to cool down, the brake fluid returned to a level just below the previous fill level.

 

Is this just due to natural expansion ? At no time did the brakes feel spongy or go off.

 

For the record:

 

The car is 1.6 x/f with live axle, with Alcon Brakes with standard master cylinder. The pads are Green Stuff

 

Brake Fluid is Castrol Response (Synthetic Super Dot 4)

 

The fluid is changed regularly (last change under 1000 miles)

I am fairly hard on the brakes.

 

Any advice,

 

Cheers

 

Peter

 

PS Anyone fitted the upgraded master cylinder with the Alcon Brakes ?

[Andrew Russell]

I have had the same problem with my master cylinder and understand it is quite common. Secret is not to overfill it and a tip I picked up from one of the Superlight racers was to fit a girls 'hair bungee' around the rim of the cap, the type which are about an inch and a half or so in diameter, elasticated and available in a range of colours. Whilst these do not prevent the leak they restrict just how far the fluid can run. Looks nice too if you clour co-ordinate!!

 

It is not advisable to choose your daughter's favourite fashion accessory though as I did. Got caught, and everytime she sees it on the Seven, I get an ear full!

 

Andrew

[DonkeyDave]

I've found this using the standard and uprated mastercylinders - especially when using slicks. I've resorted to using a pair of surgical gloves which fit very snuggly over the master cylinder and when hot the fingers of the gloves stick up giving a nice cockerel effect