Definition of discourse marker noun from the Oxford Advanced Learner's Dictionary
When an engine starts knocking, one of the first things a mechanic will check is the oil pressure. A warning light may come on in the car, and adding sufficient oil will solve the problem. Sometimes, a knocking noise is caused by loose torque converter bolts or a loose flywheel.
If the noise you hear is a fast tap or clatter near the top of the engine, it could be valve noise which would require you to have some cylinder head work done. Some noise can come from a worn camshaft. It's also a tapping noise. If the noise is a steady metallic rap, it may indicate a rod/rod bearing. A quick steady tap may indicate lifters or cam lobe, while a clatter may be loose/worn rocker arms. A low rumble or knocking noise could be caused by a bad rod bearing on the crankshaft. Here are a couple of sites that will tell you a bit more: 1  http://www.remanufactured.com/Engine_Noi...  http://www.aa1car.com/library/engine_noi....