Gimme A Brake - Feature Article by Steve Lucas

This article was originally featured in Tiger News, the Official Publication of the Cruisin’ Tigers GTO Club and was reprinted with permission from Steve Lucas.

Back in the ‘60’s, who ever heard of four wheel disc brakes? How about ABS? In 1967, power disc brakes were introduced as an option on the Pontiac GTO. I remember having disc brakes on my ’69 Goat. At the time, we were all afraid to work on them because they were new and different from drum brakes. The local brake shops even charged more money to work on them. Ironically, disc brakes were easier to change then the standard drum brakes.

With modern technology of the braking system in today’s cars, we forget how hard you had to step on the brake pedal with manual brakes to stop the car. We forgot about “fading” brakes – remember going 70-80 miles per hour then having to stop suddenly? NO BRAKES!! This is one time you can not say “They don’t make ‘em now like they made ‘em back then!”

Besides converting over to disc brakes, the only other option to improve your brakes is to keep your stock brake system in “like new” working condition. After installing new brake linings, having the brake drums or rotors turned down to a smooth surface, replacing the wheel cylinders or calipers, and having the power booster and master cylinder rebuilt or replaced, about all that is left for you to do is have the old brake fluid completely flushed out and fill the system with fresh fluid.

Brake fluid is often over-looked when doing a complete brake job. Just filling up the master cylinder after “bleeding” the brake lines is not enough. Brake fluid absorbs moisture. If brake fluid hasn’t been changed in a while (3-4 years), it probably has a lot of rusty “muck” building up in the bottom of the master cylinder, in the brake lines, and in the wheel cylinders or calipers.

Brake fluid is a form of hydraulic fluid. If is designed to work only in brake systems. Brake fluid is a chemical mixture of Polyalkyene Glycol Ether - commonly called Glycol in which each manufacturer claims that their’s does a better job. The truth is, all of them have to conform to DOT (Department Of  Transportation) standards. You have seen or heard of DOT 3, DOT 4, or DOT 5 brake fluids.

Glycol based brake fluid must have the following properties to work correctly in your car’s braking system:

·         Must have a dry boiling point of at least 400 degrees Fahrenheit - this is the temperature fresh brake fluid boils at from the heat caused by severe braking conditions.

·         Must have a wet boiling point of at least 280 degrees Fahrenheit - this is when brake fluid boils when it is exposed to moisture under the same braking conditions.

Must not freeze, compress, or corrode brake system parts, and must be compatible with other glycol based brake fluids - and must remove paint when spilled on the fender of a car (only kidding - but true! - this will only happen if it is spilled on the paint’s finish and NOT cleaned off immediately).

Going back to boiling points, DOT 4 has a dry boiling point of 440 degrees Fahrenheit and a wet boiling point of 300 degrees Fahrenheit. DOT 5 (silicone based brake fluid) has a dry boiling point of 500 degrees Fahrenheit and a wet boiling point of 350 degrees Fahrenheit. I use silicone base, DOT 5, not because of the higher boiling point, but because silicone brake fluid does not absorb water (or remove paint!). If you are going to switch from conventional brake fluid to silicone based brake fluid, you must clean and flush out the old brake fluid from the system - completely! If any of the old brake fluid is left in the system, it will not do any harm to the components, but it will effect the full advantage of using the silicone based fluid. Also, note silicone based fluid is very pricey.

I recommend power flushing the brake system because it is much easier and faster than the old method of pumping the brake pedal, then opening up the bleeder valve to let out the old fluid and air bubbles,  and repeating as necessary  until all the old fluid has been purged. Also, power flushing can be performed by one person, alone, whereas a minimum of two people are needed for the conventional flushing method. Power flushing is done by either pushing new fluid through the system or sucking the old fluid out of the system by using a vacuum pump at each wheel. When power flushing, care must be taken to ensure you have a tightly  sealed system so as not to spill any brake fluid on your car’s finish.

If you are using glycol based brake fluid, keep the cap on the can tightly closed after it has been opened. Moisture from the humidity in the air will be absorbed by the fluid in the can. Some master cylinder covers have a vent hole to allow for expansion and contraction of the fluid as the brakes are applied and released. Dirt, grease, oil, and petroleum solvents can contaminate the brake fluid. Never clean the master cylinder, wheel cylinders, calipers, or other brake components with solvents. Only use alcohol, ordinary brake fluid, or a brake system cleaner to clean these parts with.

I cleaned out the master cylinder on my blue GTO by first sucking the fluid out with a rubber squeeze bulb. (Like a turkey baster – but don’t use hers!!) After the master cylinder is emptied and cleaned out, add new brake fluid. Keep adding new fluid while the system is being “bled” of the old fluid. Keep “bleeding” the brake system at all four wheels starting at the  farthest from the master cylinder. Do this until you see clear fluid coming out of the bleeder valve. Then adjust the brake shoes (if so equipped) until you feel a slight drag as you are turning the tire when it is off the ground.