Fiberglass blocks on aft engine mount stop fitting -

On the fwd side of the aft engine mount stop fitting, you will find 2 bumper blocks, attached to the stop fitting. They look like white fiberglass pads, and when you touch them they will fall apart into small dust-like particles. Finally they are almost completely fallen apart and all you have left is a fastener with some small remainings left on it.
What do they do there? They do not have any function during the operation of the aircraft. The only function they have is to protect the aft mount stop fitting and the aft engine mount during the installation of the engine. Just to make sure the aft engine mount does not damage during the lifting of the engine and to guide the aft mount into its position.

But due to the heat which is present at that positon after the engines are stopped, these bumper-pads are disintegrating very rapidly.
Replacing these bumpers is not very effective because they will disintegrate again and they have no safety-related function during the operation of the aircraft. NEW blocks are nicely shaped with a chamfer and have a brown color. The last photo shows a bag full of old blocks where you can see some brown-color leftovers from the original color.

These bumpers can be found in :