Here’s how a bad PCV can ruin your engine – Jalopnik

We don’t mean to be a harbinger of doom, but it is unwise to continue driving if your car’s engine has a faulty Positive Crankcase Ventilation (PCV) system, especially a bad PCV valve. Continually doing this will not only decrease the enjoyment of driving, but it can also lead to catastrophic engine damage that will certainly empty your wallet. The PCV system has two main functions: it reduces harmful emissions by directing blow-by gases to the intake manifold, and it helps maintain a healthy running engine by reducing pressure build-up in the crankcase.

The PCV in a modern car consists of hoses, ventilation ducts and a one-way PCV valve. Leaking hoses can cause vacuum leaks and an engine that won’t start, but a faulty or stuck PCV valve can cause a host of symptoms. Whistling or hissing noises can mean the PCV valve is stuck in the closed position, and the warning signs can include an illuminated check engine light, oil leaks, and poor fuel economy. Meanwhile, black exhaust smoke, difficult starting, rough idling, or persistent misfires could mean the PCV valve is stuck in the open position.

Either way, a stuck PCV valve is bad news for your engine. If it goes bad, it won’t directly damage the engine. But if neglected long enough, poor PCV can lead to sludge formation and oil dilution. And when the oil is diluted with fuel and contaminants from unburned purge gases, it can cause excessive friction and damage the bearings, cylinder liners and piston rings due to insufficient viscosity. It all sounds expensive, but it doesn’t stop there. It can also clog or damage the catalytic converters, which can cost a small fortune to replace.

Most car owners may not even be aware of the PCV valve, and we can’t blame them. In most cases, it only makes itself known when something goes wrong, and it does so in big and noticeable ways. If the misfires and sputtering aren’t enough to drive you crazy, a bad PCV valve is one of the most common causes of oil leaks. When fuel vapors dilute the oil in the crankcase, the engine can burn oil and emit more smoke or spray dirty oil over the air filter. When the pressure in the crankcase becomes high enough, it can lead to oil leakage through damaged gaskets and seals. Therefore, we strongly recommend that you have a faulty PCV valve diagnosed and replaced immediately to avoid expensive and impending engine repairs.

It is good practice to inspect, clean or replace the PCV valve every 20,000 to 50,000 miles. On some makes and models, the PCV valve may be part of scheduled maintenance, so it is best to read the owner’s manual. You can clean it with carb cleaner or a degreasing spray, but it is better to replace it if the valve is seriously dirty or rusty. Replacing it is often the better option, as a new PCV valve only costs $2 to $15 depending on your vehicle. Most cars with accessible PCV systems are good candidates for a DIY solution, but a mechanic will have a better idea of ​​how to handle this on vehicles with difficult-to-access PCV valves.