Vehicles Involved: For a variety of 2002–2018 GM passenger cars and trucks powered by a V8 engine.
Condition: Customers may notice a chirp, squeak, squeal or tick sound coming from their engine.
Repair Procedure: To determine whether cam lobes are the source of the noise, use a wooden hammer handle to apply pressure to the sides of the rocker arms. A change in or elimination of the noise likely indicates a worn lobe or lifter. Also, measure the cam lobe lift at the push rod side of the rocker to compare it with other rockers on the same bank.
Should these tests not isolate the cause, visually inspect the lifter rollers and cam lobes for any damage, flat spots, pits, grooves, gouging, flaking or rusting.
If you suspect a sticking valve is producing the noise, remove the springs and seals from the valves of the misfiring cylinder; then wrap a rubber band around the tip of each valve stem. Work the valve up and down while turning it 360 degrees; if any binding is felt, a stem-to-guide clearance concern exists and should be repaired. Also, if excessive carbon is present, decarbonize the engine.
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