I’m deviating from my normal blog formula a bit this month. Instead of offering some proven, technical piece, this is more of an semi-experimental maintenance tip.
If you’ve read the blog about brake fluid (here), you understand why it is important to change the fluid out regularly, even on a street driven vehicle. And if you’ve ever changed out your brake fluid, or paid to have it changed, you also know that it isn’t necessarily cheap, in terms of time or money. I would guess that these expenses, as well as a general unawareness of brake fluid contamination issues, are the primary reasons that brake fluid is often neglected.
So, what if there was a simple method of fluid maintenance, that didn’t cost much, and could be done by anyone, in their own driveway? Well, I think that there is, and it relies on a property of particle movement called diffusion. In short, diffusion is the tendency of particles to try to level out their distribution through movement from areas of high concentrations to areas of low concentrations. Imagine dropping some food coloring into a pitcher of clear water. The color will start out as a distinct blob, and then, over a period of time, will disperse into the pitcher, changing the color of the water to a new, uniform shade. That’s diffusion.
So how does this apply to brake fluid? Simple. Water and other contaminants enter the fluid through seals, hoses, fittings, etc. Once these particles enter the system, they are free to move about the entire quantity of the fluid, and courtesy of diffusion, they do just that. Over time, the concentration of contaminants in the fluid becomes relatively equal, throughout the fluid, including the fluid that resides in the reservoir, at the master cylinder. Since this reservoir is where fluid levels are checked, and fluid added as required, it is almost always very easy to access under the hood.
So this is where the simple maintenance method comes in. All it takes is a couple bottles of brake fluid, and a turkey baster. You simply take the lid off of the master cylinder reservoir (clean the lid first, to avoid adding any more dirt to the system), suck as much of the old fluid out as you can with the turkey baster (being very careful to avoid letting the fluid drip on any painted surface), and refill with clean fluid. No need to remove the wheels, crawl under the car, find someone to pump the pedal, etc.
This clean fluid will now use diffusion to draw moisture and contaminants to it, thereby lowering the concentration in the fluid as a whole. Is it perfect? Nope. In fact, it’s nowhere near as effective as a full fluid flush. But it is very easy to do, and quite cost effective. So cheap and easy in fact, that you could do it at every oil change, or even once a month, without too much trouble. The question remains as to whether or not this procedure done 4-6 times per year is equivalent to a complete flush every two years. I’d venture to say that it is still not as good, but I’d imagine that it is pretty close, and it’s certainly better than a 3, 4, even 10 year (or longer) fluid change schedule, which I suspect is what the average daily driver is running around under now. More importantly, it can’t hurt anything, as long as you are careful to not drip fluid on the paint, and don’t pump the pedal while the reservoir is empty…I don’t know why you would, but its worth noting. It’s also worth noting that this procedure can be used on hydraulic clutch systems, as well. In either case, check your owner’s manual for the proper fluid, if you aren’t sure.
One more point…never use fluid from an previously opened bottle. You should always start with a brand new one. Small 12 oz bottles are easy to find, and relatively cheap.
