lost water from radiator. engine started running rough. pinging

Yes, that was done- starting but ran bad. was told had to put new rad. in to test the rest of the engine. Might it still run if other things are bad to ?

It was close but no I parked turned off fast. Mech. did start it to hear that was it. Just learned from him that the cap was a bitch to turn, I could never get it either. He said was on super tite, I didn't want to break it so I left it.