I too was a fan of silicone fluid until I noticed repeated failures of
the pressure type brake light switches on both my MGA and early MGB-GT.
I also had a problem with the front brakes locking up on the MGA after
converting it to silicone fluid, there are several modifications you can
make to prevent this from happening, but they all cure the symptom, not
the basic problem of incorrect seal swelling.
The straw that broke the camel's back was hearing that AP Lockheed
forbids the use of silicone fluid in systems using the Type 6 remote
servos (used stock on factory GT V-8s, Mini Coopers, and as a retrofit
for the Girling servos on MGCs). It seems that the seals on the air
control valve swell, causing the servo to lock the brakes on. If a
servo is returned to AP Lockheed as defective, and it has had silicone
fluid used in it, the company will void the warranty.
Tell me this - why should I continue to use a fluid type that will cause
failures in existing components, result in system problems, and void
warranties, whereas the DOT 4 Castrol LMA does none of the above? The
fact that silicone fluid doesn't harm paint does not outweigh the
problems. So what if you have to change out DOT 4 fluid every two years
- one of life's little pleasures is doing maintenance on my LBCs.
Cheers,
Paul Kile
1974 Factory MGB-GT V-8
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