Here is a picture showing different examples of what happens when your linear air pump fails.
You can see a dark discoloration on both the #1 and #3 air pumps caused by a build up of heat generated from a broken pump that continued to operate. This occurs when the safety screw fails to break apart when one or both of the rubber bladders tear. This allows the air pump to continue to run causing further damage as shown.
The #2 air pump is an example of when the bladders tear and the safety screw breaks like it is designed too. This saves the motor from excessive damage and in most cases allows the air pump to be rebuilt.
Here is an example of bladders that have failed in a linear air pump. Every instance is different, but most commonly you will see a tear in both bladders.
Certain brand aerobic systems require the routine replacement of air diffusers. Failure to do so can lead to poor system aeration resulting in foul odor and can lead to premature air pump failure.
Here you can see three examples of Clearstream diffusers that needed replacement.
Clogged diffusers increase back pressure on the air pump and can lead to air pump failure or diffuser breakage as shown.