Could somebody tell me where exactly is the PCV valve location on the es 350 2007. What exactly is the function of this valve, is it anyway related to the Emission ?? Appreciate your replies

 

Look at the black circle, above the black line:




Sure it's related to the emission.

 

Absolutely related to emissions. Check wikipedia's explanation:

http://en.wikipedia.org/wiki/Crankca...ilation_system

 

When u supposed to change this piece

 

Almost never? I thought you only needed to check it if you failed an e-test. Mind you, if you're going to take it out to check you might as well replace it. I don't think the part is expensive and since you're already under the hood with engine covers off etc, ...