Chain and guides fail, just like any other car replace them occasionally and you should see 250,000-400000 on a motor, may also need to feed oil as they age.I was looking at a Cobalt recently for a beater, don't really know much about them. They mostly list for so cheap I was wondering if that little ecotec tended to fail often?
Key is to only buy 2009/2010 base with a stick, they get the best mileage, have the least rust and have most of the bugs worked out, front speakers break wires and the fuel lines rust by the rear wheel, honestly have less repairs and maintenance in mine than you would a Camry