Hello all,

The most critical component in the PCV system is the PCV valve. This valve controls the amount of gases which are recycled into the combustion chamber. At low engine speeds, the valve is partially closed, limiting the flow of gases into the intake manifold. As engine speed increases, the valve opens to admit greater quantities of gases into the intake manifold. If the PCV valve becomes clogged, the system is designed to allow excessive amounts of blow-by gases to back flow through the crankcase tube into the air cleaner to be consumed by normal combustion.

Enough of the auto-shop theory lecture though, you're obviously here to learn how to test whether or not the PCV valve in your Legend needs to be replaced Here's how you would test the said valve:

1. Remove the PCV valve from the intake manifold or valve cover.

2. Run the engine at idle.

3. Place your thumb over the end of the valve. Check for vacuum. If there is no vacuum at the valve, check for plugged valve or vacuum lines.

4. Shut off the engine. Shake the valve and listen for the rattle. If valve doesn't rattle, replace it.

For a better understanding of how the PCV system looks like, refer to this Legend PCV diagram


Pretty simple, huh?