What is a rod knock, and what sort of effect can if have on your engine? To fully understand this, you must first know what a rod is and what sort of role it plays in the engine. Below is some helpful information from an Audi repair shop in Conway, AR.
The rod, also known as the connecting rod, is the part of the engine that connects the piston to the crankshaft. At the point where the rod connects to the crankshaft, there is a bearing that separates the rod from the crank journal. This bearing is made with a softer material than the crankshaft or the rod.
When the engine is first manufactured, there are some gap tolerances that get built into the engine, and that includes the rod bearing to crankshaft journal. Here, the tolerance is put in place to allow a certain amount of oil to pass through from a hole in the crankshaft journal and stay on the surface of the bearing. Oil films form on the bearing and keep the two parts from rubbing against each other during standard operation. If this space opens up too much from general wear and tear or deformation of any type, the oil no longer develops a proper film, which results in rod knock.
The noise referred to as “rod knock” occurs as a result of metal on metal contact between the crankshaft journal and the bearing during the engine cycle’s power stroke. If the situation is particularly bad, it can be caused by the rod striking the crankshaft journal at the point where the bearing is displaced.
Rod knock is most commonly caused by a spun bearing—the bearing typically spins in the end of the rod, which forces it out of its standard position. This typically happens as a result of the rod cap stretching during abusive, harsh driving situations. It can also be a result of improper lubrication—there might not be enough oil in the engine, or the oil that is there could be flowing incorrectly through the system. Any of these potential causes, or any combination of them, could result in rod knock.
Rod knock is a serious issue with your engine—it means the engine is not functioning properly. If you start to notice rod knock, this isn’t a problem that will just resolve itself—you must take immediate action and replace the rod bearing while also fixing any other parts associated with the sound. If you do not take action quickly enough, you might need to replace the engine entirely.
So how do you know if it’s rod knock that you’re hearing? Rod knock typically sounds like a low-pitched knocking sound that can be heard deep in the engine. As the engine speeds up, the frequency of the noise will increase, but you can hear it at any engine speed. If you hear a type of knocking sound that disappears after the engine warms up, this is likely not rod knock.
Any time you hear a knocking sound in your engine, be sure to get your vehicle to a trusted Audi repair shop in Conway, AR like Riverdale Automotive.