How do i know if my engine mounts are bad ?

Take a look at them and if they aren't holding your engine to the cross member snugly anymore then I would say they were bad. They are part rubber and part metal - kind of like a 'clubhouse sandwich' of rubber and metal. A quick visual inspection would tell you their condition. You might need a mirror to see the one on the drivers side...

You could try wiggling the engine back and forth/side to side and see if they have any slack...

Ok.. there not broke, so i guess they are ok..