car keeps over heating even after water pum and thermostat was replaced. keeps making this real crazy rattling noise when it gets hot especially when i hit the gas. does anyone know why this is happening and if so what do i do? does needing a new muffler have anythingh todo with my engine overheating?

Not good if the engine is rattling when you are overheating. Can cause engine damage. Did you bleed the cooling system and checked the radiator fan operation? The radiator fan should come on at 108C.

Your intake or head gaskets are leaking coolant into the oil and the lower end is knocking because coolant washes the oil off the bearings. Check the oil for milky look. If it is, stop driving it and fix it asap.