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These days, replacing rotors is standard maintenance

  • Article by: PAUL BRAND
  • May 25, 2012 - 3:50 PM
Q The past six GMC vehicles I've owned were low-mileage used vehicles. The first major problem is always brake rotors and pads. I fight tooth and nail with the dealership to have something done.

I noticed that your reply to the lady buying a used, low-mileage vehicle included: "The vehicle may need routine tire and brake replacement." Tire replacement is a given and a no-brainer. What is your meaning as to routine brake replacement and especially the rotors? Brake pads I understand, and I treat them as I would tires.

I would like someone one to tell me what to do to make this situation less costly. Just like clockwork, I can expect in the next year or so to have to pay out $800 to $900 to have all four rotors replaced on my vehicle, which has less than 38,000 miles. How can I avoid this?

A I've always considered brake rotors -- like brake pads -- as "consumable" components. Granted, back in the day rotors seemed to last longer, but today's motor vehicles no longer use asbestos and feature more aggressive metallic and ceramic friction materials that operate at higher temperatures and generate measurable wear on brake rotors. The benefit is better stopping power and fade resistance. The price is more wear on the rotors.

I'm also not a big fan of turning brake rotors. Today's rotors are already close to their minimum thickness when new. By thinning the rotors, their ability to dissipate heat is reduced. causing more rapid wear and distortion. It is possible to "true" a slightly warped rotor, but once significantly worn, warped or out-of-round, it's time for replacement. You certainly can shop brake work among dealers and independents, and aftermarket brake rotors are often significantly less expensive.

I think it's time for you to accept the fact that replacing brake rotors once or twice during the life of a modern motor vehicle is relatively normal and routine.

Q I have a 2005 Mercury Mariner with 135,000 miles on it. I've been told by a dealer that it needs brakes. The steering wheel does shake at high speeds when applying the brakes, but my vehicle info center says the brakes are OK. I've also been told major parts in the front end also need replacing for $700 to $800.

A The shake when applying the brakes is typically caused by a problem with the front brake rotors. They are either worn, warped or out of round. When you apply the brake pedal, the uneven surface of the rotor kicks the brake pads back causing the master cylinder to pulse the brake pedal. The dealer or shop should be able to show you the wear, run-out or out-of-round with a dial indicator. Specifications for warping or run-out is 0.0005 inches and thickness variation is 0.0002 inches.

The vehicle information center will tell you only when the brake pads are worn, not when the rotors are warped. So, your vehicle does need brakes. At this mileage, I would replace both front rotors and brake pads as well as check the rear brakes.

Q I have a 1991 Mercury Colony Park station wagon with slightly more than 100,000 miles. It's a beautiful car with an unusual quirk. The car starts and runs perfectly, but when it is warmed up and I shift into park, the car immediately dies. It will start right back up with a turn of the key, idle and run just fine. Any thoughts would be most appreciated.

A Contamination in the idle air bypass valve might be causing this stalling. I'd start by cleaning the throttle body and idle air bypass valve with an aerosol carburetor spray as outlined by Ford in technical service bulletin 91257 from December 1991. Also, make sure ignition base timing is correct and that the oxygen sensor is responding quickly enough to insure correct fuel-air mixtures.

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