1. Bleeding the Brakes: This is the most common cause. Air in the brake lines will significantly impair braking performance. You MUST bleed the brakes completely after any brake work, especially caliper replacement. Use a brake bleeder kit and follow these steps:
* Proper Order: Bleed the brakes in the correct order to ensure efficient air removal. Generally, it's farthest wheel from the master cylinder first (often a rear wheel, then the other rear, then front passenger side, then driver's side), but consult your Alero's repair manual for the specific order.
* Two-Person Job: One person pumps the brake pedal slowly and firmly while the other opens and closes the bleeder valve on each caliper.
* Consistent Flow: The fluid should flow steadily. If it's intermittent or pulsing, there's still air in the system.
* Full Reservoir: Keep the brake fluid reservoir topped off throughout the bleeding process to prevent air from being sucked back in.
2. Caliper Piston Issues:
* Proper Installation: Ensure the calipers are correctly installed and the pistons are seated properly. A slightly misaligned caliper can bind, preventing the pads from making full contact with the rotor.
* Seized Piston: Even new calipers can have seized pistons. If you didn't replace the pistons, they might be sticking. Inspect for free movement and lubricate the piston boots with a silicone-based brake lubricant (never petroleum-based).
* Caliper Slide Pins: The pins that allow the caliper to slide on the bracket can seize. Inspect these for free movement. Clean and lubricate them with silicone-based brake lubricant.
3. Brake Pad Issues:
* Correct Pads: Did you use the correct brake pads for your Alero? Incorrect pads won't fit properly or may wear down unevenly.
* Pad Thickness: Ensure the pads are adequately thick. Thin pads won't engage correctly with the rotor.
* Pad Placement: Make sure the brake pads are correctly positioned within the caliper.
4. Rotor Issues:
* Warping: Warped rotors can cause pulsation or uneven braking. Check for warping visually or with a dial indicator. If warped, you may need to replace or have them resurfaced (machined).
* Corrosion: Excessive rust or corrosion on the rotors can interfere with braking. Clean them thoroughly with a wire brush.
5. Master Cylinder:
* Fluid Level: Check and top off the master cylinder fluid level. Low fluid can result in spongy brakes.
* Master Cylinder Failure: In rare cases, the master cylinder itself might be failing. This is less likely if the brakes were working before the replacement.
6. Other Potential Problems:
* Vacuum Booster: A malfunctioning vacuum booster can reduce braking power.
* Brake Lines: Check for leaks or kinks in the brake lines.
Troubleshooting Steps:
1. Re-bleed the brakes thoroughly, paying close attention to the technique and the consistent flow of fluid.
2. Inspect the calipers for correct installation, free-moving pistons and slide pins.
3. Inspect the brake pads and rotors for any issues.
4. Check the brake fluid level in the master cylinder.
If you've checked all these points and the brakes still aren't working correctly, seek help from a qualified mechanic. Brake failure is a serious safety issue; don't attempt to drive the vehicle until the brakes are functioning properly. A professional can diagnose any more complex problems.
