Touch One Thing, Something Else Breaks

You all know how this goes. Everything is working fine but you decide to just tweak this one little thing and then ...I had a diesel mechanic come over to check my engine. It seemed to be vibrating more than it used to and also needed a 500 hour valve adjustment. So he checks the alignment, no problem. Checks the valves, a little tweak here and there but essentially no problem. But, oh by the way, did you notice your fan belt is wearing. Should probably replace it.So, ok, I go into town and buy a fan belt. Lovely no name Japanese version. I install it and within 10 minutes it blows up. Humm, could be defective so I went back and bought another belt. Installed it and within 10 minutes it blows up leaving pieces of fan belt all over the engine compartment and an overheating engine. Ok, so enough of that for the day. Close everything up and go to the marina for a fiesta. We are retired you know!Saturday morning I get up and decide to find the root cause - my old Quality management days we