Energy from exploding fuel is what powers your engine, and some of the vapors from those explosions escape into the lower part of the engine, which is called the crankcase. These gases are made up of nearly 70 percent unburned fuel. If the gases are allowed to remain in the crankcase, they can quickly contaminate the oil and turn it into sludge. Sludge is one of the biggest enemies of your engine—and it eventually leads to engine failure. The pressure build up can also cause seals and gaskets to blow, which is why the gases need proper ventilation.

Gasoline engines used to include a hose that let the poisonous fumes vent out into the air. Since 1963, the federal government has required gas engines to have a special one-way valve installed to help reduce dangerous emissions.

The positive crankcase ventilation valve routes crankcase gases through a hose and back into the air intake system where they are re-burned in the engine. Clean air is pushed into the crankcase through a breather tube. The re-circulating air removes moisture and combustion waste from the crankcase, preventing sludge. This extends not only the life of your oil, but the life of your engine too. The PCV relieves pressure in the crankcase, preventing oil leaks.

Eventually, your vehicle’s PCV valve will become gummed up. Once that happens, it can’t move enough air through the engine to keep it working efficiently. If the PCV valve is sticking enough, it will result in oil leaks, excess oil consumption, and a failing intake system. If you experience surging, hesitation, or leaking oil, it could mean that your PCV valve needs to be repaired.

Consult your owners' manual for recommended PCV replacement intervals. Most manufacturers recommend having it replaced between 20 and 50 thousand miles. However, some manufacturers don’t list intervals for PCV replacement.

Usually, we can diagnose PCV system problems with a visual inspection. Fortunately, PCV valve replacement is both quick and inexpensive. Proper oil changes will greatly extend the life of the PCV valve. Skipping a few recommended oil changes can allow varnish and gum to build up in the valve, reducing its efficiency.

If you have had your car for a while and this is the first you've ever heard of a PCV value, ask your tech to check yours out or call Loren's Auto Repair at 406-755-7757.