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What is a Mustang's PCV Valve and What Does It do?

Written By: Ryan Doyle

Every engine produces some blow-by, especially on cold starts. Giving a proper place for all of that blow-by pressure to go will keep your seals intact and allow for correct operation of your Mustang.

Mustang PCV Valve – Key Facts

Installed PCV Valve
  • A PCV valve is located on the passenger side valve cover on many Mustangs and is connected to the intake manifold
  • The PCV system siphons harmful vapors from the crankcase and routes them into the intake manifold
  • Installing a catch can on your vacuum line will catch the “blowby” caused by vapors and oil passing from the crankcase, preventing any unwanted buildup in the intake tubing and the throttle body
  • PCV valves are sized specifically for certain engines, and the wrong valve can flow too much or too little air causing drivability problems

Where is a Mustang’s PCV Valve Located on the Engine?

The main component in the PCV system is the PCV valve, which is usually located in the valve cover (1996-2018 Mustangs. 1979-1995 Mustangs have them on the back of the lower intake right about where the upper intake bolts to it). A hose connects the PCV valve to the intake manifold. A second hose between the air cleaner and crankcase or other valve cover (V6 or V8 applications) provides fresh air to help flush the vapors out of the crankcase. Some engines have a separate air filter for the PCV breather hose located inside the air cleaner.

What Does a PCV Valve do for My Mustang?

Motorcraft PCV Valve

The blow-by vapors that end up in an engine's crankcase contain moisture, as well as combustion byproducts and unburned fuel vapors. The crankcase is sealed to prevent the escape of these gases into the atmosphere, but the vapors must be removed to prevent oil contamination that leads to sludge formation building up in your motor, as well as your intake tubing. The positive crankcase ventilation (PCV) system siphons these vapors from the crankcase and routes them into the intake manifold so they can be re-burned in the engine.

Do I Need a Catch Can for My PCV Line? 

Sludge can buildup in your intake tubing if your PCV valve is not doing its job well enough. To prevent this buildup (and especially necessary for Mustangs with forced induction), installing a catch can on your vacuum line will prevent any unwanted buildup in the intake tubing and throttle body. The positive crankcase ventilation (PCV) system siphons these vapors from the crankcase and routes them into the intake manifold so they can be reburned in the engine. Higher horsepower Mustangs suffer from blow-by more so than stock Mustangs. If you’re running much more power than in stock form, you might want to throw a catch can on your PCV line and play thins safe. Just remember to empty the can once in a while.

How does a Mustang’s PCV Valve Work? 

PCV Components

The PCV valve is a spring-loaded valve with a specific orifice size designed to restrict the amount of air that's siphoned from the crankcase into the intake manifold. This is necessary because air drawn through the valve from the crankcase has a leaning effect on the fuel mixture much the same as a vacuum leak. Airflow through the valve must be controlled within certain limits. At idle, airflow is reduced because little blow-by is produced. When the engine is cruising and vacuum is high, airflow through the PCV valve is at a maximum to purge the blow-by vapors from the crankcase.

What is Blow By, and Do I Have It?

The term itself, blow-by, means the fuel air mixture blows past the piston and into the crankcase. The PCV (Positive Crankshaft Ventiliation) is designed to remove the excess liquid from the crankcase. The vast majority of engines have this issue although the PCV system does quite a supurb job as a remedy for the problem. You will not feel a difference on a cold engine vs a warm engine.

When Should I Replace My Mustang’s PCV Valve? 

It's important to note that PCV valves are sized for specific engine applications. The wrong PCV valve for an application can flow too much or too little air causing drivability problems. Varnish deposits can clog the valve, so replacement for preventative maintenance is recommended (every 50,000 miles usually). Note that the 4.6L modular motors have had issues with PCV valves going bad before the 50,000 mile mark. A quick check to see if your PCV valve is still in good working order is to remove it and give it a shake. If you hear it clearly rattling, it’s still good, if not, it’s time for a new one.

Note - 2005 to 2010 Mustang GTs have no mechanism in the the PCV valve plumbing.

Why are Some PCV Valves Heated? Do I Have One?

Generally speaking, lower trim models did not have heated PCV valves. Certain trims, such as the Bullitt or GT500, came with a heated PCV. Certain GT models came with a heated PCV, but this was not uniformily distributed across all GTs. The 03-04 Cobras did not come with a heated PCV valve. The primary benefit of having a heated PCV is the removal of the freezing risk. While the risk of the PCV freezing is extremely small, even in cold climates, it is still a possibility.