DOT 4 Hydraulic Fluid

I love DOT 5. Man I’ve had in my scoot for 20 years (I should be ashamed) with not a problem. DOT 4 hydraulic fluid is hydrophilic (picks up moisture) and corrodes paint. I’d like to convert my 2005 FLHR to DOT 5. Know they cannot be mixed. What’s involved? Can I wash/rinse my hydraulic brake system with a cleaner (alcohol or the like) and then make the switch or do I have dissemble everything, clean replace some items, and then switch? Dot 4 is supposed to have a better “feel,” well can’t go by me.


The entire system must be taken apart and all rubber components replaced with DOT 5 compatible pieces. You cannot just flush the system or you would be playing with fire. I recently ran into this problem on a car with a proportioning valve, disc front and drum rear. I always had soft pedal because of the small amount of mixed fluids trapped in the valve. Mixing the two will create an oil and water consistency that will heat up quick, evaporate quickly and hold moisture quick but not stop you quick. Don’t run your fluids that long flush and bleed every two years.   Wrench Safe, FMH
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