Without a positive crankcase ventilation valve, also known as a PCV valve, combustion gases from a BMW's combustion chamber get into the crankcase and cause smog in the environment. The unused combustion gases are also commonly known as blow-by. The PCV valve in a BMW works by connecting the crankcase to the intake manifold. The connection creates a vacuum in the crankcase that draws gases from the breather into the intake manifold. From the intake manifold the combustion gases go into the PCV valve and are burned by fresh air.
Locate the PCV valve and loosen the clamps using a torque wrench. The PCV valve in the BMW is located behind the intake manifold. It may be necessary to remove the intake manifold to have enough room to locate the PCV valve.
Remove the hose from the PCV valve. Replace the hose and clamp if they appear to be worn, have cracks in them or are leaking. Remove the hose by gently clamping it with your angled needle-nose pliers and pulling it out.
Remove the PCV valve with your angled needle-nose pliers. If it is pressed into a rubber grommet, check to see if the grommet is worn. If so, replace the grommet.
Thread the new PCV valve in by hand to avoid damaging it.
Tighten the valve until it is secure. Do not overtighten as this could damage the valve.
Replace the hose and clamp to the valve.
Start the BMW's engine and check to make sure there are no leaks in the PCV valve or hose.
