* Worn or broken piston rings: This is a major cause. Worn piston rings allow combustion gases to leak past the pistons into the crankcase, increasing pressure. This is often accompanied by excessive blue smoke from the exhaust.
* Valve guide seals: Similarly, worn or damaged valve guide seals can allow combustion gases to leak past the valve stems into the crankcase, building pressure. Again, blue smoke from the exhaust is a common symptom.
* PCV (Positive Crankcase Ventilation) system malfunction: The PCV system is designed to vent crankcase gases. If it's clogged, restricted, or failing, pressure can build up and force oil out.
* Blocked crankcase breather: Similar to a PCV problem, a blocked breather will prevent the escape of gases, leading to pressure buildup.
* Head gasket failure: A blown head gasket can allow combustion gases to enter the crankcase, dramatically increasing pressure. This often manifests with other symptoms like coolant in the oil, white exhaust smoke, or loss of coolant.
* Crankcase ventilation filter (if equipped): If your engine has a separate crankcase ventilation filter, a clogged filter can prevent proper venting and cause excessive pressure.
Less common causes:
* Overfilling the engine with oil: While less likely to blow oil out the dipstick, overfilling can increase pressure.
* Extremely high engine temperatures: Excessive heat can cause expansion of gases, contributing to pressure build-up.
What to do:
This is a serious problem that needs immediate attention. Do not continue to drive the vehicle. Continued operation could cause significant engine damage. You should have the engine inspected by a qualified mechanic to diagnose the root cause and perform the necessary repairs. Ignoring this problem can lead to catastrophic engine failure.
