Anyway, I get them to do an engine diagnostic and tell them about the whistling noise. They do the diagnositc. Find an oil leak and oil all over my spark plug. We replace plugs, plug wires, the hole where the leak was coming from. They test drive it...figure out the whistling noise. The fan that cools the motor isn't switching on.
Very little here makes much sense.
I am guessing that the valve cover was leaking but hard to say,can`t imagine how the fan switch and lack of the fan turning would make a whistling noise unless somehow it was overheating and blowing off steam and coolant.
For anyone here that doesn`t already know it......If the engine is making a knocking sound of any kind DON`T drive or run it,period.
More then likely if it is knocking the horse is out of the barn and rolling in new bearings will not help,the crank journals will probably have to be turned.
Short of a failure of the oil pump the main thing that causes this is lack of maintenance as has been stated by others here.