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.
One of the most common symptoms associated with worn engine mounts are impact noises coming from the engine bay. Worn, damaged, or broken motor mounts can cause clunking, banging, and other impact type sounds as a result of the weight of the engine shifting excessively to the point of contact.