89 560SL rear brake squeak???

[Mauidieselpetr]

50kmiles, nice rotors 10mm, almost new MB pads, adjusted parking brake,and any time in reverse after steping on brake, squeak from driver rear brake!!!
Any experiences, cure???
Thank you very much
Petr

[Alkraut]

It is possible that the noice is from some contaminant like sand that got between the pad and the rotor, but more likely it is due to high frequency vibration that creates noise, The vibration is due to small amounts of movement between the pad and the caliper. This causes local friction and noice. Typical brake squeal.

There are a couple things to do. It might require removal of the pads. This is not hard, but may require you to push back the pistons (one on each pad, both sides of rotor). First, and easiest is to check the pins and "cross-shaped anti rattle spring that is on the top side. If the spring is loose, it can allow movement and squeal. The pins drive out with a small diameter punch and have a little circular ring spring to hold them tight. Note the position of the cross spring, it should be held down by the pins, and the perpendicular cross section should be applying pressure to the top edge of the pads. If these parts look bad, you can buy the hardware kit that includes the pins and spring. I ordered mine from a local Advance Auto store. Fastlane and others have them as well.

The pads should have a thin shim between the piston and the back of the pad. It is the same shape as the pad itself, and has ears/holes for the pins as well. These help prevent squeal. The pads should have a coated material on the piston side, that is sandwiched between the shim and pad. That helps prevent squeel. There is anti-squeal compund that is sold in parts stores. It is a high temp blue silcone RTV-like material. If everything looks OK, you could remove the pads and put a small amount between the shim and pad. If shims are missing, you can buy them separately as well. Good Luck.

[balsa]

Originally Posted by Alkraut

It is possible that the noice is from some contaminant like sand that got between the pad and the rotor, but more likely it is due to high frequency vibration that creates noise, The vibration is due to small amounts of movement between the pad and the caliper. This causes local friction and noice. Typical brake squeal.

There are a couple things to do. It might require removal of the pads. This is not hard, but may require you to push back the pistons (one on each pad, both sides of rotor). First, and easiest is to check the pins and "cross-shaped anti rattle spring that is on the top side. If the spring is loose, it can allow movement and squeal. The pins drive out with a small diameter punch and have a little circular ring spring to hold them tight. Note the position of the cross spring, it should be held down by the pins, and the perpendicular cross section should be applying pressure to the top edge of the pads. If these parts look bad, you can buy the hardware kit that includes the pins and spring. I ordered mine from a local Advance Auto store. Fastlane and others have them as well.

The pads should have a thin shim between the piston and the back of the pad. It is the same shape as the pad itself, and has ears/holes for the pins as well. These help prevent squeal. The pads should have a coated material on the piston side, that is sandwiched between the shim and pad. That helps prevent squeel. There is anti-squeal compund that is sold in parts stores. It is a high temp blue silcone RTV-like material. If everything looks OK, you could remove the pads and put a small amount between the shim and pad. If shims are missing, you can buy them separately as well. Good Luck.

I have a 1986 560sl. There are no shims for front brake pad only for rear ones. This is info from my web research.

1. Should I apply anti-squeal paste on back of front pads?

2. Also if I put rear pads shims the anti-squeal paste should be applied only between the shim and pad and not on the other side of shim that contacts the caliper?

Thanks, Balsa

[Alkraut]

I have used the anti-squeal compound directly between the pad and disc. I have done it on other cars, but should be ok on your MB. It should not cause any issues if it is applied in the area where the pistons contact the pad backing plate. Apply a small amount. Don't worry if it smears onto other places when you install pads. It stays pliable.