Tapping Sound from Engine

Some 2020-2021 Encore GX and 2021 Trailblazer models equipped with the 1.3L engine (RPO L3T) may have a tapping sound coming from the engine that may sound similar to a valvetrain tick or tap noise.

Using the J-39570 Chassis Ears, it may be determined that the sound is coming from the engine block below the cylinder head area. To identify the source of the sound, cancel each cylinder to isolate the affected component.

Following the diagnostics in the Service Information for “Lower Engine Noise, Regardless of Engine Speed,” remove the piston and rod assemblies (Fig. 18), which includes the piston pin retainers (#1), piston pin (#2), piston (#3) and connecting rod (#4). Once the piston/rod assembly is removed, place and hold the rod flat on the end of a workbench. Center the piston/wrist pin in the small end of the rod and rock the piston back and forth along the axis of the piston pin.

 

Fig. 18

 

A noisy assembly will have a loose feel when the piston is rocked back and forth in the direction of the piston pin axis. It may help to compare to other assemblies in the engine. Replace any loose piston rods/pins to correct the tapping sound condition.

 

– Thanks to Raymond Haglund

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