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Jim Grant Tech Tips Jim Grant Tech Tips
A collection of helpful articles based on reader submissions
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Below is a collection of Jim Grant's Tech Tips sorted by Vehicle Make. These Tech Tips were answers to questions submitted to Jim by users over the course of many years.
If you have any questions, please feel free to email us.



Lincoln - Mercury
  Jim Grant's Tech Tips

'02 Hyundai Sonata GLS, Brake Whirring

Q: Upon accepting delivery of our new '02 Hyundai Sonata, we noticed a whirring noise like you hear when you drive onto a warning strip on the edge of a highway, when braking from a speed of 40mph to a stop. No, I don't have anti-lock-brakes. The demonstrator of same model and description doesn't have that sound. The dealer started guessing and wanted to grind the brakes down and turn the rotors and I told them no! This is a new vehicle and I don't need guess work, that's why I traded my '99 vehicle in!

- Jim G.

A: I guess you could say you have new brakes. If a customer were to come into our shop and say that their new brakes were making a whirring when braking, I would inspect the machined finish of the brake rotors. Why is that? The contact area of the brake pads to the braking surface must be smooth and non-directional. There are 2 common problems we see. 1. The brake rotor has machine work that makes it look like an old vinyl record. There will small groves that you can feel as you drag your finger nail across the braking surface of the rotor. 2. A cross hatch pattern that has grooves that you can feel similar to the grooves in problem number 1. The brake pads on today's vehicles are of a high metal content. This type of brake pad will not get along with brake rotors that have too rough of a machined finish. The result of this disagreement is a whirring noise that can be heard when the brakes are applied. Over time the machined surface of the brake rotor will smooth and quiet down, but I cannot tell you how long that will take. If you were my customer and the new brake rotor finish was proven to be the cause of the noise, the brake rotors would be replaced.

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