Q: Engine is making loud knocking sound. Is it the rod bearings?

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I was driving on the freeway and when i got out, the car started making a very loud knocking sound. I pulled over and inspected the engine. I found that the coolant, and oil were at normal levels. The oil is a normal color. There is no strange smoke or fumes from the tailpipe or the engine. The temp gauge was at normal levels. The engine makes the noise when it idles and runs. The car is a bit old eith 200k+ miles and had been sitting for a while. The air filter, oil, oil filter, valve cover gasket, coolant, differential oil, battery and thermostat have been replaced. Could it be the rod bearings?

My car has 200000 miles.
My car has an automatic transmission.

Before you condemn the motor for having rod or crankshaft knock you should have the crankshaft harmonic balancer checked for a broken one. If it is bad then it can cause a loud knocking noise. Replace it if it is broken.

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