Don’t Drain Brake Fluid Routinely

Question: I recently read that it is advisable to change brake fluid every year or 30,000 miles. The reason is that apparently water can accumulate in the fluid over time and affect the safety of the brakes. Do you agree?--E.L.S.

Answer: It is true that brake fluid has an affinity for water and readily absorbs it. Unlike many fluids in your car’s mechanical system, brake fluid is not a mineral oil. It is a polyglycol, a synthetic material broadly related to the alcohol family, and mixes well with water.

Brake fluid performs the important job of transmitting the braking force from your brake pedal inside the car to the brakes at the wheels. Under tremendous pressure, the fluid is forced through small tubes to the wheels, where the fluid actuates tiny pistons that push the brake pads and shoes against rotors and drums. The resulting friction stops the car.

Water contamination of brake fluid causes two problems. First, it can cause spongy brake action, in which the pedal does not seem to reach a firm stop. This is the result of water and air compressing inside the fluid lines, which does not occur with brake fluid. It also results from the water boiling, which can occur because brake temperatures can reach 1,000 degrees.

The other problem caused by contamination of brake fluid is that the water corrodes the internal parts of the hydraulic system. Most often, the brake master cylinder and wheel cylinders or calipers can become internally corroded. That causes both internal and external leaks, which will eventually deplete the system of fluid or cause loss of hydraulic pressure, a very serious safety problem.

For all the problems that contaminated brake fluid can cause, however, many car manufacturers do not list changing of brake fluid in owners’ manuals as required maintenance. In some cases, the service is recommended as optional in the technical shop manuals used by garage mechanics.

The problem with changing brake fluid as a routine service is that it is becoming a much more involved and complicated procedure on newer brake systems, and if it is not done properly, it will cause a lot of other problems.

Product Test

One of the most common complaints about cars from readers involves engine ping--that annoying knock from under the hood when the engine doesn’t seem satisfied with the octane rating of the gasoline you have purchased.

I recently wrote a column about a new product produced by Chevron and called Pro-care Clean-up. Its main ingredient is Techron, a proprietary substance that is supposed to remove engine deposits, reduce the octane requirements of an engine and relieve ping.

As part of a product test, I circulated bottles of Clean-up among a variety of motorists with older cars and asked for their opinion of the product. It was mostly favorable, with many people saying it seemed to reduce engine knock.

The owner of a 1982 Honda Accord with more than 100,000 miles on his car reported that ping was noticeably reduced after treatment with Clean-up. But another Honda owner who has a Civic said it did not do anything for his car.

The product improved the performance of a 1982 Volvo (with 100,000 miles on it) that has needed premium fuel for the last several years. “I noticed some improvement in performance, particularly acceleration, after using Pro-care. Also, hesitant starts were reduced,” the owner said.

A 1980 Subaru owner reported that her car “knocked and pinged something awful.” After a one-tankful treatment, the problem was reduced somewhat, she said.

The owner of a 1974 MGB with severe engine ping reported that his car was helped initially, but that after a couple of tankfuls of gasoline without the treatment the clatter had come back, though not as badly as before.