Brake squeal can be caused by many things. Original equipment Toyota brake pads come with anti-squeal shims and brake grease that goes between the shims. Where the brake pads "sit" in the brake caliper mount also has hardware/clips that locate the brake pads in the caliper mount. If any of these clips are missing or installed incorrectly the brakes will squeal. Brake pad material and the condition of the brake rotors greatly contribute to brake pad noise too.
MY WIFES 2007 CL230c MB has a squeak or squeal when she backs it out of the garage or parking 1st thing in the morning. The MB dealer looked at the brakes and told her that this was common on the 230 class of auto. This started right after she ran over glass going through an accident and had a flat tire as a result??? Help