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.
The knocking noise is the piston rods hitting on the main rod bearings because there is no lubrication. Because of the lack of oil and probably the excessive frictional heat, the rod bearings and the rocker arms have worn to the point that they are loose and will continue to knock and tick.he knocking noise is the piston rods hitting on the main rod bearings because there is no lubrication. Because of the lack of oil and probably the excessive frictional heat, the rod bearings and the rocker arms have worn to the point that they are loose and will continue to knock and tick.