My experience with silicon brake fuid

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PvD

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In the 1970s, 80s and 90s silicon brake fluid was promoted since it did not absorb H2O resulting in lower boiling point. I restored a Jensen Healey in the late 1980s to early 1990s and also serviced the brake system of the 6.9.
The Jensen Healey brake system was renewed except for the master cylinder which had been overhauled not long before I started the restoration. The Jensen Healey has been on the silicon brake fluid for over 23years and the only item requiring any attention was the master cylinder which was replaced 2 years ago.
The 6.9 brake service work included new seals in the back cylinders, flush the system with metho and flush/fill system with silicon brake fluid. The 6.9 was fine for about 20years, then after about 10km run the brakes failed going out down Bells Line of Road. Replaced the master cylinder and again the brakes failed after about 10km. Stripped the front brakes which had H2O in them which boiled resulting brake failure. Cleaned the front brake cylinder fitted new rubbers and no more brake failures.
The silicon brake fluid does not absorb the H2O but any H2O entering the system will migrate to the lowest point, in my case being the front brake cylinders. Although one does not need to bleed brake systems with silicon brake fluid it may be wise to the check the brake cylinder every so often.
Michael Parker checked the suspension system earlier this week and he commented the brake pedal appears to go right down to the floor. The brake pedal felt normal to me when driving the car home. The silicon brake fluid has the reputation that the brakes feel different/soft.
 

c107

and 111/116/124/126
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I don't know why more manufacturers don't use mineral oil like Citroen Did (and RR did using a derivative of the same system).

You can find a rusty old Citroen that has been in a paddock for 10 years and the braking system will be just fine with no rust. If you use the same fluid as is usd in the power steering system you don't even need to specify another fluid type (they can still be separate systems).
 

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