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Q: Knocking sound when idling or stopped 1993 Chevrolet Lumina APV

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There is a rhythmic knocking sound coming from the left side of the engine (facing the engine from the front) near the serpentine belt. On the road you can't really hear it, it gets really loud when idling at a light. Then in park and running it's still there just not as loud.

My car has 230000 miles.
My car has an automatic transmission.

A: Hello - the rhythmic knocking you hear coul...

Hello - the rhythmic knocking you hear could be something driven by the serpentine belt (i.e. AC compressor) or the belt itself. It is also possible that this an internal noise - like the timing chain, which is immediately behind the serpentine belt on the engine. Removing the serpentine belt, then starting the engine for 20-30 seconds won’t harm the engine, but would narrow the problem to inside the engine or something belt-driven. I would recommend getting this checked out soon, as additional damage may be occurring while you drive further. A mobile, professional mechanic, such as one from YourMechanic, will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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