Questions and Answers

Mercury Grand Marquis Spraying Oil All Over
Q. A neighbor has a 1991 Mercury Grand Marquis with a 302 with an automatic transmission and 100,000+ miles. This has always been a good car and well cared for. Some time ago, it suddenly started using lots of oil. No signs of burning it, but more like blowby.

There is an accumulation of oil in the air cleaner, an oil mist coming out of the oil fill spout, and oil everywhere under the hood. The PCV valve is working okay. I thought maybe bad or broken rings, but there is no sign of an engine miss, plugs do not foul.

Engine starts easily, runs smoothly at all rpms, even gets decent gas mileage. There is no smoke in the exhaust.

He took the belt off the AIR pump because either it or the A/C compressor was making a lot of noise, but I can't see that causing the problem.

A. It's a problem with the PCV system. The Positive Crankcase Ventilation (PCV) Valve is designed to prevent blow-by gases and/or crankcase vapors from being emitted into the atmosphere. This is achieved by venting a sealed crankcase to the intake manifold, via a regulating one-way check valve.

Blow-by gases, and crankcase vapors, contain HC, CO and NOx emissions, which result from incomplete combustion, piston rings-to-cylinder walls wear, and normal engine operation. These gases and vapors are formed when part of the ignited air/fuel charge is forced past the piston rings into the crankcase by the pressure of combustion.

The PCV Valve opening is regulated by an internal spring, intake manifold vacuum, and crankcase pressure. The valve is normally located within a hose (1/2" to 3/4" o.d.) between the crankcase and the throttle body or intake manifold.

Typical PCV System

While the engine is running, air is drawn into the crankcase from the air cleaner assembly to be mixed with the blow-by gases. As the PCV Valve opens, manifold vacuum and crankcase pressures route the air-diluted blow-by gases into the induction system to be burned.

If the PCV Valve should become stuck closed, the system routes excess crankcase pressure and vapors back through the ventilation hose and air cleaner assembly into the induction system.

So what you need to do is check the PCV hose between the PCV valve and the intake. You'll find it's probably collapsed and cracked open since oil will deteriorate the inside of the hose over time.