Wow, how timely. I just put new shocks on the Jeep and geez, I bet you the break fluid hasn't been changed in this beast for a while. Well certainly not in the last four years. I know these things have to be taken care of, but I have to admit I do not know how often it should be done. I guess I had better learn quickly how to change out the break fluid. This is a job you surely don't want to screw up as those breaks are mighty important.
On Jul 8, 2008, at 11:48 PM, Ray Boyce wrote: > Many manufacturers recommend changing brake fluid every two years. As > procrastinators, we usually wait until the brakes need major work > and then > assume everything was changed. The fluid may have been changed at > that time, > but not always. It depends on the type of brake work done, and > operating > with old brake fluid in your vehicle can decrease brake performance > and > cause expensive brake parts to malfunction sooner. > > > > There are several types of brake fluid on the market. The most > common is DOT > 3. Brake fluids must meet standards set by the Society of Automotive > Engineers (SAE). DOT 3 (Department of Transport) fluid must have a > minimum > boiling point of 401 degrees F, be compatible with other materials > in the > brake system, have anti-corrosion properties and mix with other DOT > 3 fluids > without changing chemical properties. > > Some European car manufacturers specify DOT 4 brake fluid. Like DOT > 3, this > is a glycol-based fluid, but it has a higher boiling point. DOT 4 > boils at a > minimum of 446 degrees F. This higher boiling point is necessary on > vehicles > expected to generate a lot of heat in the braking system. When brake > fluid > boils, vapour bubbles are created in the sealed brake systems. When > you step > on the brake pedal, the brake pressure compresses the bubbles, not > applying > the brakes with full force. Braking performance decreases and the > pedal > feels soft or spongy. > > One of the problems with glycol-based brake fluids is that they are > hygroscopic. They attract moisture out of the air into the fluid. > Leave a > can of brake fluid open on the bench or leave the cap off your brake > master > cylinder and the fluid becomes contaminated with water. Moisture can > even be > absorbed slowly through the seals in good braking systems. Water > boils at > only 212 degrees F (100C), so this significantly lowers the boiling > point of > the brake fluid. DOT 3 fluid with only 3% water in it boils at only > 284 > degrees F. This is 115 degrees lower than clean brake fluid. DOT 4 > fluid > boils at 311 degrees F, 135 degrees lower than clean DOT 4 fluid. You > probably wouldn't notice this in every day driving, but if you had > to brake > hard, then the additional heat in the brake system could boil the > fluid and > you find yourself with poor performing brakes. > > Water in the brake fluid also causes corrosion. Parts such as wheel > cylinders and brake calipers are not too expensive to replace, but > those ABS > hydraulic units can easily add a thousand or more to the repair bill. > Changing the fluid will not only improve braking performance but > prolong the > life of hydraulic brake components too. > > Silicone brake fluid, usually referred to as DOT 5, doesn't absorb > moisture > from the air, and it won't attack painted surfaces like glycol-based > fluids > if you spill it on the fender or grille, but it is not without > faults. The > viscosity of silicone brake fluid is different than DOT 3 and DOT 4 > fluids, > so most manufacturers don't recommend it for use in systems with ABS > brakes. > The biggest disadvantage of silicone fluid has to be that it is more > difficult to seal. DOT 5 fluids will seep past seals and gaskets > that would > normally contain DOT 3 and DOT 4 fluids. > > One of the big advantages of DOT 5 silicone fluid is it has a higher > boiling > point than DOT 4, boiling at 500 degrees F. Silicone brake fluid and > Glycol-based fluids should not be mixed. The complete system needs > to be > disassembled and cleaned before filling it with silicone fluid. > > What's new in brake fluids? Non-silicone based synthetic brake fluids. > Sometimes referred to as DOT 5.1, it is compatible with DOT 3 and > DOT 4 > brake fluids. This fluid is advertised as "synthetic" but has much > the same > characteristics as DOT 3 and DOT 4 fluids. This biggest advantage is > its > higher boiling point of over 500 degrees F, similar to silicone-based > fluids. As long as the container says it is compatible with DOT 3 or > DOT 4 > fluids, you can mix it or top up the brake system with this > synthetic fluid. > Better yet, take the vehicle in for service and have the old fluid > bled out > and new fluid installed in your brake system. The brakes will perform > better, and you will have delayed the onset of more costly brake > repairs. > > [Non-text portions of this message have been removed] > > > Scott Howell [EMAIL PROTECTED] [Non-text portions of this message have been removed]
