* Low oil level: The most basic cause. Check your oil level immediately. If it's low, you need to add oil *carefully* and then determine *why* the oil level is low (leak, consumption, etc.). Driving with low oil is extremely damaging and could have already caused significant damage.
* Oil pump failure: The oil pump is responsible for circulating oil. A failing pump won't provide sufficient pressure, leading to the light and knocking. This is a major repair.
* Worn engine bearings: The knocking sound is almost certainly due to the engine bearings being starved of oil. Without sufficient lubrication, they're grinding against the crankshaft, causing the knock. This is extensive engine damage and will likely require a rebuild or engine replacement.
* Clogged oil filter or pickup screen: A clogged filter or pickup screen restricts oil flow, reducing pressure. This is less likely to cause the severity of knocking, but is still a problem that needs addressing.
* Leaky oil cooler: An internal leak in the oil cooler can cause low oil pressure.
* Rod bearing failure: A particularly bad scenario, this is where the connecting rod bearings fail, leading to catastrophic engine damage. The knocking is a very serious indication of this.
What NOT to do:
* Do not continue driving the car. Driving with low oil pressure will severely damage the engine, leading to costly repairs or even a complete engine failure. The knocking is a major warning sign that immediate action is needed.
What to do:
1. Check the oil level immediately. If it's low, add oil (the correct type and amount) and then assess why it was low.
2. Have the car towed to a mechanic. Do not attempt to drive it. A professional diagnosis is crucial to determine the extent of the damage and the necessary repairs.
3. Prepare for significant repair costs. Depending on the cause, repairs could range from relatively inexpensive (oil change, filter replacement) to extremely costly (engine rebuild or replacement).
The combination of the oil light and knocking is a serious sign of engine trouble. Ignoring it will likely result in irreparable engine damage. Get the car to a mechanic ASAP.
