* Worn or damaged bearings: This is the most likely culprit. Low oil pressure indicates the bearings (connecting rod and/or main) are worn, allowing excessive clearance and leading to insufficient oil film between the moving parts. The valve clatter strongly supports this. Worn bearings are usually caused by lack of oil changes, low oil levels, or using the wrong type of oil.
* Oil pump internal failure (despite visual inspection): Even if the pump looks okay, internal components like the gears or pressure relief valve might be damaged. A thorough inspection by a mechanic is needed, possibly including disassembly and testing of the pump.
* Leaking oil cooler: A leak in the oil cooler can bypass oil pressure, leading to low pressure at the engine's critical components.
* Damaged or cracked engine block: A crack in the engine block can allow oil to leak, leading to low pressure. This is less likely but possible.
* Clogged or restricted oil passages: While you checked the pan and pickup, there could be restrictions further in the engine's oil passages (internal). This often requires professional inspection and potentially cleaning or repair.
DO NOT continue to run the engine. Running the engine with low oil pressure will cause catastrophic damage, leading to a complete engine failure. The valve clatter indicates that parts are already rubbing against each other without sufficient lubrication, causing scoring and further damage. Significant repair costs – potentially a rebuild or engine replacement – are highly likely if you continue to operate the vehicle.
Recommended actions:
1. Immediately stop driving the vehicle.
2. Have the vehicle towed to a qualified mechanic. Describe the symptoms completely.
3. Get a proper diagnosis: A mechanic will need to inspect the engine thoroughly, possibly including a pressure test of the oil system to pinpoint the exact cause of the low oil pressure.
Ignoring this problem will result in very costly repairs or even a need for a replacement engine. Addressing it promptly is crucial.
