What a noisy door closer is telling you

A bang at the end of the swing

That is latch speed, and it is the one thing on this page that a valve fixes. Slow the latch valve half a turn at a time until the noise stops, then check the door still latches from half open. The two settings pull against each other, and it is easy to cure the bang by creating a door that no longer shuts.

A squeak or grinding through the movement

Noise that follows the door rather than arriving at the end of it is mechanical, and the hinges are the usual answer before the closer is. A closer in good condition is close to silent through the swing, so a squeak that tracks the movement is more often the door hanging on dry or worn hinges than anything inside the body. After the hinges, check the arm, its pivot points and the connection to the frame — fixings tight, pivots moving freely. Slowing the closer makes any of this quieter without making it better.

A knock or rattle at the body

Usually fixings. A closer works against the leaf every cycle, and a screw that has loosened lets the body move against the door each time. Left alone this enlarges the holes, which is a harder repair than tightening a screw. Check the fixing-hole centres against the drawing if the holes have already opened up.

A closer that has become noisy and slower at the same time is worth looking at for oil. Lost damping and new noise together usually mean the body, not the arm.