I have a 1985 W123 230E Mercedes Benz with the M102 engine, single row timing chain. Mileage is 115k. I noticed this morning a grinding / rattling sound coming from the front of the engine. The noise is not particularly loud but I like to solve problems before they get worse. The noise is most noticeable with the engine idling at approx 900 rev/min. Reved up to 1,500 rev/min, the noise is still there but is being drowned out by the sound of the engine. I put a screwdriver on the water pump and alternator and with my ear at the end of the screwdriver I couldn't hear the noise passing through. I suppose the way to eliminate both is to remove the fan belt and run the engine. I will do this tomorrow. The water pump is relatively new - replaced 3 years ago. Age of alternator unknown. With the engine running I removed the oil filler cap. I could not hear the noise inside the engine. Any ideas chaps? Chain tensioner? Timing chain? I don't know the history of either. Anything else I can do check? I have changed the oil regularly and the engine runs just fine.