* Parking Brake Mechanism: The most common culprit is the parking brake (emergency brake) system. When you're in reverse, the slight movement of the car can cause the parking brake shoes or cables to slightly engage and rub against the drum or rotor, creating a squeak. This is especially likely if the parking brake isn't fully released. Over time, the parking brake components can wear down and become more prone to sticking or binding, making the squeak worse.
* Brake Caliper or Pad Issues (less likely): While less probable than the parking brake, a sticking caliper piston or unevenly worn brake pads *could* theoretically cause more noise in reverse. However, this would usually manifest as noise in forward gear as well, making the reverse-only squeak less likely to be this cause. If it is, it's probably a very minor sticking problem.
* Moisture or Debris: Moisture or small debris accumulating on the brake components, particularly on the rear brakes, could lead to squeaking, especially when the reverse gear engages and the components are moving differently than in forward gear. This is a temporary fixable problem, though.
* Contaminants on Rotors or Drums: Brake rotors or drums can accumulate brake dust, dirt, and other debris that can lead to squeaking, especially if the braking action is slight, as it often is with reverse.
Troubleshooting:
1. Check the Parking Brake: Make absolutely sure your parking brake is completely released. Try releasing and re-engaging it a few times firmly. If the squeak persists, this is the most likely area to investigate.
2. Listen Carefully: Try to pinpoint the location of the squeak. Is it definitely coming from the rear of the car? This strongly points towards the rear brakes or parking brake mechanism.
3. Inspection: If you're comfortable working on your car, you could carefully inspect the parking brake mechanism and rear brakes for signs of wear, rust, or debris. However, this is best left to a mechanic if you're not experienced.
4. Professional Mechanic: If you can't easily identify and fix the problem, taking your Celica to a mechanic is the best option. They have the tools and expertise to diagnose and repair the issue accurately.
In summary, the reverse-only squeak strongly suggests a parking brake problem. Addressing that first is the most efficient troubleshooting step.
