Unlocking the Secrets of the Braking System
Question: I have a Lincoln Mark VII with an anti-lock braking system. These types of brakes are new to me. The brakes developed a jerky feeling when I tried to stop the car. I complained to the dealer, but was told it was a normal feature of the brake system. After 18,000 miles, I had to have the rotors replaced, because the pads had not fully retracted. After the repair, I no longer experienced the jerky sensation from the brakes. Do these new anti-lock brake systems differ from older brakes in terms of their feel and do newer pads wear out more quickly? --K.D.W.
Answer: An anti-lock brake system has sensors on the wheels that report to a computer when a particular brake locks up or begins to skid on the pavement. If a lockup occurs, a computer takes over and orders the system to begin pulsing the brake, in a somewhat similar fashion to a manual pumping of the brake to prevent a loss of control.
But in an anti-lock system, the pulsing is very quick--roughly 12 times per second. Every system works differently, but generally the pulsing occurs so quickly that you could not really detect it from the feel of the brake pedal.
If you experience a pulsing or jerking from the brake, it is far more likely that it was caused by a defect in the brake rotor or drum than it was from the anti-lock system. A warped rotor or out-of-round drum can cause pronounced pulsating in the brake pedal.
The failure of the pad to retract is not uncommon. In older drum systems, the brake shoes are pulled back from the drum by strong springs. But in a disk brake system, the pads are pulled back from the rotor (or disk) by the resiliency of rubber seals. As these seals age or are damaged by contaminated brake fluid, they can fail to do their job. The result is that the pad will ride against the rotor and wear out prematurely.
If your rotor was warped, it could have caused the pad to wear out even without a failure of the rubber seal. A warped rotor will wobble as it rotates, thereby scraping the pad as it turns. Eventually the pad wears out and the metal backing plate will damage the metal rotor.
Pads no longer contain asbestos, but that does not mean they wear out faster. The new semi-metallic pads are quite hard and actually outlast the older asbestos pads. In addition, they don’t cause lung cancer.
Q: Arco’s new EC-1 gasoline is marketed as a substitute for leaded gasoline, but does not contain lead. Since it is cheaper and has higher octane than unleaded, why could I not use it on my newer car that uses unleaded fuel? --L.L.K.
A: You could use it, except for one problem. The nozzle on the EC-1 pump is designed to fit the neck of a gas tank that takes leaded gasoline. The nozzle is too big to fit a neck for unleaded fuel. As a marketing decision, Arco wanted to limit the fuel as a leaded fuel substitute.
Ironically, the fuel does not contain a lead substitute. Rather, Arco believes that unleaded fuels pose little harm to older engines designed for leaded fuels. The reasoning is that unless the engines are subject to high loads at high engine speeds, there is little chance of engine valve damage. Owners of many classic cars disagree, but Arco and other refiners insist they have tests and technical data to back up their claims.
Vartabedian cannot answer mail personally but will attempt to respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, The Times, Times Mirror Square, Los Angeles 90053.
