Discovery II problems

I was driving my 99 LR Discovery up an incline, power was not so good then a bang/grind sound came from the engine and then knocking sound with minimal power as I drove the Disco back home (less than a mile). The temp gauge was not hot. My wife told me she added more oil as we have the signature leaks. She added too much oil (the dipstick was over the mark by an inch). Would the frothy excess oil issues cause the engine problems? What else might it be? Oil pump, water pump? The engine was also smelling hot for a week. The gauge never ran hot and the oil never got lower than 3/4 full. Thanks.