Help me explain what he did wrong...

Rod looks to be cut close enough to being on par with the other chamber. If thats an auto slack adjuster, it will take up slack and go back into spec with several hard pumps of the brake. I just put all new chambers, slack adjusters and s-cams on my whole truck becuase it was time. Several of them wouldnt keep adjustment so i just did whole truck. There is a way to test the slack adjuster as per instruction manual. BAck off one full turn and put a box wrench on adjuster nut. Have a helper pump the brakes and observe that the box wrench is rotating toward adjustment. If your slack adjusters are ok and your inner s-cam bushing is trashed, just a little free play in your cam bushing will make your pushrod go way out of spec when brakes are applied. chock your wheels and release your brakes. Pull up and down on yours slack adjuster to see if that has a bunch of play. IF there is, then you need to remove your slack atjuster and pull off the camshaft tube and replace the s cam bushing in there. ITs simple to do.

 

very simply. everytime you replace a brake booster the brakes (slack adjuster) needs to be adjusted. not applied you should have a 1/16`` between your brake pad and drum. this equals a stroke length of 2 1/4`` at the brake pushrod. brake wasnt adjusted.