Yup. Hi guys. Lots of people recommend changing it; no one ever does. The theory is that moisture is absorbed from the humidity in the air through the rubber hoses which are porous. Brake fluid boils at well over 400 degrees. Water boils at 212 degrees which is real easy to hit from prolonged city driving. The moisture vaporizes and cause a spongy brake pedal. That's one form of brake fade.
Moisture also promotes corrosion of metal parts. Getting every drop of old brake fluid out is not nearly as important as when draining engine oil. The more you replace, the better for the system. If you have something to suck the old fluid from the reservoir, do that first, then fill it with fresh new fluid from a sealed container. Never leave a container of brake fluid open because it will suck moisture out of the air, then you haven't accomplished anything. Open the bleeder screws at the wheels and just let them gravity-bleed for a few minutes. Don't let the master cylinder run empty or you'll have air to bleed out. That can lead to a lot of headaches on Fords. Once you're done with all four wheels, refill the master cylinder only as full as it was when you started. The level was down if the front disc brake pads are partially worn. When it's time for them to be replaced, you'll have to push the pistons back into the calipers and the fluid behind the pistons will get pushed back up into the reservoir. If you fill it now, there won't be any place for that fluid to go and it will spill over and make a mess.
Also, if you use anything to suck fluid out of the reservoir or a funnel to pour it in, be absolutely certain there is no hint or residue of any type of petroleum product. The least little bit of contamination will destroy ALL of the rubber seals, o-rings, and hoses that come in contact with that fluid. That is a real expensive and time-consuming repair, and if there is an anti-lock brake hydraulic controller on the vehicle, it might not be worth repair. I have to mention that because I read about that happening a lot here and most people aren't aware how serious that is.
Tuesday, May 10th, 2011 AT 10:31 PM