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.
Engine noise under the hood may be caused by loose torque converter bolts, low oil pressure, spark knock or excessive piston clearance. A cracked flywheel on an automatic transmission or excessive connecting rod clearance may also cause an engine to knock. Continue Reading.