* Caliper Pistons: Seized or sticking caliper pistons can cause uneven pad wear and a crunching sound. The pistons might not be retracting fully, allowing the pads to drag slightly against the rotor. This is a common issue on older vehicles. You'll need to inspect the calipers and potentially rebuild or replace them.
* Caliper Slides: The metal pins that allow the calipers to slide smoothly along the bracket can seize due to rust or corrosion. This prevents the calipers from moving freely, leading to uneven pad contact and noise. Grease and/or replacement of the slide pins is often necessary.
* Rotors: Warped or scored rotors can cause a crunching noise, especially at low speeds. Even with new pads, a damaged rotor will make contact unevenly. A visual inspection will show scoring or warping. Resurfacing rotors might be possible, but often replacement is necessary.
* Brake Shield/Back Plate: The metal shield behind the rotor can sometimes rub against the rotor or caliper if it's bent or damaged. Check for any contact between this shield and other brake components.
* Parking Brake: Ensure your parking brake is fully released. A partially engaged parking brake will definitely create noise.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine the brake calipers, rotors, and brake shields for any obvious damage, corrosion, or sticking.
2. Caliper Movement: Try to manually move the calipers in and out to check for smooth operation. If they're stiff, they need attention.
3. Rotor Condition: Inspect the rotors for scoring, grooves, or warping. A perfectly flat rotor should be smooth. Use a straight edge for an accurate check.
What to do next:
If you're not comfortable working on brakes yourself, take your Windstar to a qualified mechanic. Brake problems are serious and should be addressed by someone experienced. Improper brake repair can be dangerous.
The fact that the noise is only at low speeds strongly suggests a problem with caliper movement, rotor condition, or the brake shield, rather than a pad issue. The mechanic will be able to diagnose the exact cause and perform the necessary repairs.
