What would make a tapping noise when vehicle is turned on then noise quits after ten minutes?

Answer 1

1. One or more lifters in the valve train system may be stuck in the compressed position due to sludge or other buildup from less than optimal oil change periods. As the engine warms up the combination of heat and warm oil softens the buildup enabling the lifter to expand and remove any slack in the valve train.

2. One or more lifters and the camshaft may be worn past the expansion limit of the lifters thus creating slack in the valve train. As the engine warms up the parts in the valve train, primarily the lifter and push rod expand and remove the slack. This type will eventually wear past the limits of expansion and become continuous tapping. Again this may be cause by less than optimal oil change periods. If the onset of tapping was shortly after an oil change where the engine had a "cleaning treatment" performed, the cam and lifters were probably severely damaged during the treatment. Engines with such damage may continue with little or no additional damage with proper maintenance however there is no guarantee. 3. If the tapping is very light, as opposed to the louder, heaver sound of lifters, it may be the fuel injectors. These always make some noise but as the engine reaches operating temperature the noise usually decreases to the point it is obscured buy the other noises from the engine.