I have a 1985 Mercedes 300SD with 92,000 miles. It was my Dad's car and drove only in the summer. Everything seems to work i.e. car sits for a long time but vacuum door locks etc all work fine. The car is slow on acceleration but shifts smoothly. An intermittent squeal comes from near the motor mounted air cleaner but isn't the air cleaner. If you are driving the car and the rpm is around 3000 and you slightly let up on the throttle, a one to two second squeal occurs noticeable inside the car. I've tried to find it under the hood - my 11 year old can hear it too but the clackety clack makes it hard to diagnose under the hood! Thinking of EGR, turbo etc? Anyone else having any issue like this? It's not the belts - the noise is higher than that and I've retightened all with no effect.