Miscellaneous engine noises
(1) A strong dull noise that becomes more rapid as the engine accelerates indicates worn or damaged crankshaft bearings or an unevenly worn crankshaft. To pinpoint the trouble spot, remove the spark plug wire from one plug at a time and crank the engine over. If the noise stops, the cylinder with the remove plug wire indicates the problem area. Replace the bearing and/or service or replace the crankshaft.
(2) A similar (yet slightly higher pitched) noise to the crankshaft knocking described in the previous paragraph, that becomes more rapid as the engine accelerates, indicates warn or damage connecting rod bearings. The procedure for locating the problem cylinder is the same as described in paragraph 1.
(3) An overlapping metallic noise that increases in intensity as the engine speed increases, yet diminishes as engine warms up indicates piston cylinder wear. To locate the problem cylinder, use procedure described in paragraph 1.
(4) A rapid clicking noise that becomes faster as the engine accelerates indicates worn piston pin or piston pin hole. The sound will happen each time the piston hits the highest and lowest points in the stroke. The procedure for locating the problem cylinder is the same as described in paragraph 1.
(5) A metallic clicking noise coming from the water pump indicates worn or damaged water pump bearings or pump. Replace the water pump with a new one.
(6) A rapid tapping sound or clicking sound that becomes faster as the engine speed increases indicates "valve tapping" or stuck valve lifters. This can be identified by holding one end of a section of hose to your ear and placing the other end at a different spot along the rocker arm cover. The point where the sound is loudest indicates the problem valve. Adjust the valve clearance if applicable or replace the lifter. If multiple lifters are clicking on an engine with hydraulic lifters, check the oil pressure.
(7) A rapid clicking sound that becomes faster as the
engine speed increases can also indicates an exhaust manifold leak. This can be identified by holding one end of a section of hose to your ear and placing the other end near each exhaust manifold where it mates to the cylinder head. Exhaust manifold leaks tend to be louder when the engine is cold. They also can become louder when the engine is under load.
(8) A steady metallic rattling or rapping sound coming from the area of the timing chain cover indicates a worn or out-of-adjustment timing chain. Service or replace the chain and related components.