Braking System:
* Worn brake pads: This is the most common cause. As brake pads wear down, the metal backing plate can contact the rotor, creating a thumping or grinding noise, especially during deceleration. This is usually accompanied by a squealing or grinding sound as well, but the squealer tab might be worn.
* Warped brake rotor: Heat from braking can warp the rotor, causing it to rub unevenly against the brake pads, resulting in a thumping sound. You might also feel a pulsation in the brake pedal.
* Loose caliper: A caliper that's not properly secured can move slightly, causing uneven contact with the rotor and a thumping sound.
* Sticking caliper: A caliper that doesn't retract fully can cause the brake pads to drag against the rotor, leading to a thumping noise and possibly overheating.
Suspension System:
* Worn ball joint: A worn ball joint can create a variety of noises, including thumping, especially during braking and deceleration as the extra load stresses the joint.
* Worn tie rod end: Similar to a ball joint, a worn tie rod end can contribute to a thumping sound, particularly when turning and braking.
* Worn wheel bearing: A worn wheel bearing can create a humming or rumbling noise, but it can also manifest as a thumping sound, especially under load (like deceleration). Often this will change pitch with vehicle speed.
* Loose wheel: A simple but important check. Make sure the lug nuts are tight.
Other Possibilities (Less Likely):
* Something stuck in the wheel: A stone or other debris lodged in the wheel or brake assembly could create a thumping noise.
Troubleshooting Steps:
1. Visual Inspection: Carefully inspect the right front wheel and brake assembly. Look for obvious signs of wear on the brake pads, warped rotors, loose components, or damage to the suspension.
2. Test the Brakes: Carefully test the brakes. Do you feel any pulsation in the brake pedal? Is the thumping sound more pronounced when braking harder?
3. Jack Up the Vehicle: Safely jack up the right front of the car and support it securely with jack stands. Rotate the wheel and listen for any unusual noises (wheel bearing). Try to wiggle the wheel – excessive movement indicates a problem with the ball joint or tie rod end. Check for play in the wheel by grabbing the top and bottom and trying to move it in and out.
4. Check the Lug Nuts: Ensure all lug nuts are properly tightened.
If you are not comfortable performing these checks yourself, take your Cavalier to a qualified mechanic for a proper diagnosis and repair. Ignoring a thumping noise can lead to more serious and expensive problems down the line.
