When engine idling occasionally there is a noise that sounds like a belt slipping but have replaced tensioner and both belts. Could it be a pump?
noise sounds like slightbelt slipping. on 1998 BMW 750iL
Possible a noisy idler pulley, i am assuming the tensioner assembly (pulley and tenisoner) were replaced, leaving the idler pulley left. It is unlikely the pump to make an intermittent squeal noise unless it the oil was low to a point. Even still the groan when they starve