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DOT 5 Brake Fluid - Tried it?[850/1995] posted by Bill Meacham on
Saturday, 21 March 1998, at 12:59 a.m.
Anyone tried flushing their brake system using the silicone fluid (DOT 5) as a replacement? Advantages are: DOESN'T ABSORB MOISTURE and doesn't screw up your paint if/when you spill it.
Bill
86 740T
Re: DOT 5 Brake Fluid - Tried it?[850/1995] posted by Steve Seekins on
Sunday, 22 March 1998, at 9:26 p.m.
I have one of my Volvos (79 242GT with 83 I/C turbo engine) set up with DOT 5 fluid. If you are goind to do this, you must completely disassemble the system. YOu cannot do the replacement by just flushing the new fluid through. The DOT 3-4 fluids do not mix with the silicone based DOT 5, and the old fluid is heavier than the silicone. THis means that the caliper bores will remain filled with the old fluid as the silicone fluid will come into the bore and simply rise to the top and be bled out the bleeder nipple. The old fluid will end up saturated with water and the corrosion will eventuallly destroy the calipers.
So, to do the job, you must remove the pistons from the calipers (good idea to replace all seals and dust boots) completely clean them and blow them dry so that no old fluid remains anywhere in the system (including the equalizing valves in the rear brake lines if not ABS equipped (and there currently is no silicone fluid approved for ABS systems as far as I know).
Is it worth it? Perhaps for that collector car that gets stored all winter and is only driven on Sundays and holidays, but for the daily driver, good quality DOT 4+ fluid is fine (VOLVO, Castrol LMA, or ATE Super Blue) provided that you perform a complete brake system flush with new fluid at least once every two years (if you have hydraulic clutch, be sure to bleed that system also!!
Volvo Club of America