* Low Oil Level: The most common and easiest to check. Check your dipstick immediately. Low oil means the pump can't draw enough to maintain pressure at low speeds.
* Worn Oil Pump: The oil pump is responsible for circulating the oil. If it's worn out, it won't generate sufficient pressure at lower RPMs. This is a serious problem requiring repair or replacement.
* Clogged Oil Pick-Up Screen or Tube: The oil pump draws oil from the sump through a screen and tube. If these are clogged with sludge or debris, the pump can't get enough oil.
* Worn Engine Bearings: Worn bearings create larger clearances, requiring more oil to maintain pressure. At idle, the oil pressure may be insufficient to keep the bearings properly lubricated, leading to a drop to zero. This is a very serious issue and requires immediate attention to avoid catastrophic engine damage.
* Faulty Oil Pressure Sensor or Gauge: While less likely given the symptom, a faulty sensor or gauge could give a false reading. However, a complete drop to zero suggests a real problem, not a faulty sensor.
* Leaking Oil Pressure Relief Valve: If the relief valve is stuck open or leaking, the oil pressure will be lower than normal. This valve is designed to relieve pressure when it gets too high, but a malfunction will reduce oil pressure.
What to do immediately:
1. DO NOT CONTINUE DRIVING. Running the engine with zero oil pressure will cause catastrophic engine damage very quickly.
2. Check your oil level. Add oil if it's low, but don't overfill.
3. Have the vehicle towed to a qualified mechanic. This requires professional diagnosis and repair. Ignoring this problem will likely lead to a very expensive engine rebuild or replacement.
The cause needs to be diagnosed and fixed immediately to prevent significant engine damage. The longer you drive with zero oil pressure at idle, the more likely you are to have a major engine failure.
