Ford Repair: brakes, replacing brake pads, mercury monterey

Question
I own a 2006 mercury monterey and recently the brakes started to squeal a high pitch off and on at low or high speeds.  Pushing brakes sometimes made them quit or when you turned the wheel.  The car has 60,000 miles and they were original brakes.  They still had plenty of pad left, but I pulled the rotors, had them turned and replaced pads with wagner thermo quiet.  I 100 or so miles later and now they are squealing again with the same symptoms.  Having my father previously owning a auto parts store and I turned some rotors for him, we suspected the inner and outer turned rotor could be a problem.  My father thought it would vibrate if there would be an issue.  I plan to take it to a mechanic, but don't really want to replace the pads again.  Any thoughts on why it is doing this again?  Warped rotor?  Thanks

Answer
Noise is common in disc brakes, but if it happens frequently it can be annoying. One thing I always do as part of replacing brake pads is lubricate the caliper slides, especially where the pad touches the bracket. These days many techs also put brake lube on the back of the brake pads. I do not, never saw the benefit of that practice, but it is fairly common now. You want to use a BRAKE CALPIER LUBRICANT, no just any old grease. Brake grease for disc brake is usually silicone based, and withstands the high temps created by braking. The pads should also have a backing on them, all in the attempt to stop high frequency vibrations that can cause squealing.

I cannot see the surface of your rotors, so no way for me to tell if it is done properly. Thermoquiets have been around a long time, but none of the shops I worked for used them so I have no first hand experience with them. Sometimes there can be particular mating characteristics of brake compounds that simply leads to noise. Perhaps the thermoquiets don't agree with your rotors, or the finish on them.

Also make sure nothing is rubbing on the rotor besides the brake pad friction surface, like a dust shield or brake pad clip.

A little brake squeal occasionally may be consider normal, if it is frequent then it needs attention. Applying the brakes puts enough force on the parts to eliminate the noise, but you don't want to drive around with the brakes applied!!