Rick's Free Auto Repair Advice

PCV Valve Rip Off

Is a PCV Valve a Rip Off

Shops ALWAYS recommend replacing your PCV valve. But that’s just their normal PCV valve rip off routine. Before I explain how the rip off works, you need to know a bit about engines. Think of the piston and cylinder like a doctor’s syringe. The rubber tip on the plunger is the piston. If you look closely at the rubber tip, you’ll see several rings around it. Those rings press against the side of the syringe and seal it so it can push the medication through the needle. But in an engine, those rings are made of metal and each ring has a gap in it so it can be spread apart and placed on the piston. As the piston compresses the air/fuel mixture, some of those gases work their way around the rings and through the gaps. These gases are called “blow-by.” Even brand new engines right off the assembly line have blow-by. Older worn engines have more of it. So you end up with flammable gases constantly entering the engine crankcase. If those gases are allowed to build up, they will eventually force their way through the oil pan and valve cover gaskets and cause oil leaks. But that’s a best-case scenario.

In the old days, car makers used to just vent those gases onto the road. Yeah, very polluting. To eliminate that pollution, they started installing a Positive Crankcase Ventilation (PCV) system. In that design, the gases are sucked out of the crankcase by the vacuum in the intake manifold. Fresh filtered air is brought into the crankcase to replace the flammable gas. But if the vehicle ever experiences a backfire through the intake, that fire can flow backwards into the crankcase and literally blow up the engine. To prevent that, car makers install a one-way valve called the PCV valve. Its job is to allow blow-by gases to flow from the crankcase to the intake manifold, but not the other way around.

Now let’s talk about the rip off. The PCV valve usually sits in a rubber gasket near the top of the engine. Most manufacturers recommend replacement at around 70M miles. But since they suck blow-by gases out of the engine, they’re also exposed to hot oil mist. In extreme cases, that oil mist can build up inside the valve and gum up the one-way check valve. If the check valve cannot move, you lose protection against engine damage in the event of a backfire.

Now here’s the scenario. You go in for an oil change. The shop barely breaks even on charges for the oil change. So they look for additional items to sell you. The technician removes the PCV valve and shows it to you. It’s dirty and covered with oil. He says, “Your PCV valve is dirty and needs to be replaced.” Of course the PCV valve is dirty! It sits in the engine and sucks blow-by gases and dirty oil mist. Put a brand new one in and take it out 10 minutes later and it will look the same! That doesn’t mean it’s gummed up and needs to be replaced. The REAL test for a PCV valve is to shake to see if the check valve plunger moves freely. If it does, it’s FINE. So instead of just nodding your head and giving your consent to replace it, ask the tech to shake it. You should hear a crisp metallic clicking sound. If you do, it’s good. If the valve doesn’t move, moves slowly, or makes more of a dull sound, replace it.

Friends and family members who have their oil changed at these places report that they’ve been hit up for a new PCV valve EVERY SINGLE TIME THEY HAVE THEIR OIL CHANGED. Remember, the manufacturer recommends changing it every 60-60M miles.

You can buy a PCV valve at the auto parts store for about $3. The oil change places charge $12. It’s a rip off, especially since you probably don’t need to replace yours.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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