keeping them running
Page 79
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by Trevor Long croft
Vhen a vehicle comes into a vorkshop with a leaking hydraulic nake seal, few fitters would be ikely to realize at first that conaminated brake fluid which las been left in too long could )e the reason behind the failure.
Brake fluid is generally a regetable oil. Mixing it with -nineral oils such as paraffin or 3etrol will cause natural seals to ;well and disintegrate. So correct storage • of the fluid and cleanliness when overhauling a fluid Drake system can prevent premature failure.
In order to clear up any confusion, I asked Girling for some general hints about hydraulic brake system maintenance.
When filling a fluid reservoir, pour fluid directly from the tin it was supplied in, I was told. If an intermediate container or a funnel is used, it must be exclusively set aside for fluid. Cleaning a funnel/ container previously used for petrol will not do!
If the fluid in the system is already contaminated it is safe only to pump a proprietary cleaning fluid or industrial methylated spirits through the system to clean the pipes. The same fluid should be used to clean all the components and then all the rubber hoses and seals must be replaced. Before fitting new seals wash your hands in order to remove, for instance, traces of paraffin or petrol remaining from a previous job.
For their own braking systems Girling recommend that fluid is replaced after 18 months. I was told that most brake fluids absorb water from the atmosphere and as a result their boiling point is lowered. When the fluid remains in the system for too long there is a possibility that its boiling point will drop to a dangerous level, and the brakes will not work at all because the vapour evolved from the hot fluid is compressible: fluid is not.
The ingress of fluid from the atmosphere is also critical. if the fluid is not stored in a sealed container its boiling point could be appreciably lowered even before it is used. For every one per cent increase of water content, the boiling point of Girling Crimson fluid drops by 50deg F. Other fluids can drop by even more.
Brake fluid is very like some lubricating oils and so containers must be clearly marked in order to avoid confusion.