Belt broke on my 2003 mercedes s500 and I replaced it for it to break just hours later wondering what is wrong or what else might need to be replaced

 

Your belt tensioner or idler pulley is frozen you need to replace those too

 

I would check all turn (std bearing pulleys, alternator, water pump, aircon, power steering etc. In my case it was water pump. When they start to go they leak a tiny bit from shaft so you might see some green fluid on the rack going across bottom below, or on the belt see white green almost powder stuff from it flinging off belt when it drips. Also when a bearing goes and you look at the pulleys from the side you’ll normally see the offender off at an angle where the rest are all parallel to each other!
You did get routing right? It started and went around then slipped off easily. I failed even though I’d taken a picture until I saw this 🙄 You have to get the tensioner to the max and put a pin in put belt in place then pull pin. Easiest way unless someone helping. Hence in pic of tensioner see supplied at full compressed..
1. Routing Pic
2. Eg Can see my water pump skewed in
3. A12 star ring spanner fits on tensioner and didn’t use the female hole rather the one that stuck out on mine.
4. Learned from looking for a 12 star multi point 17 socket all these bolt heads will fit that ring/socket
5. What my tensioner looked like 03 S320cdi
6. Spline I was going to use until I counted a ring spanner and it clicked. This idiot hadn’t seen that for years 🤔🤨🙃
Mine had another tensioner pulley at 1oClock too.
Hope that helps you.
Have a good one

 

Good post!

In my case, the air conditioning compressor locked up.

With the belt off, every pulley driven by the belt should turn smoothly and quietly. Replace any that make noise or are hard to turn (the compressor will be a bit stiff, but should turn smoothly).