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Discussion Starter · #1 · (Edited)
My PCV valve is due for replacement for the third time since my owning the vehicle. When the dealer replaced the part the second time I was told that the part was defective. Has anyone else experienced the same issues? Doing research, I found that it’s uncommon for this part to go bad and need to be replaced. Is this part coved by state emissions law? I live in NY state.
 

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How long have you owned your vehicle and what model/model year? How many miles on same?

The PCV is a very heavy wear component. It's right up there with coolant thermostat & water pump and emissions O2 sensors. It's quite common for it to go bad in many vehicle use environments.

As such it's not warranty "covered" as it's a "wear & tear" item in most locations, but I can't speak for New York state emissions requirements. As some states freely cover windshield replacements for better visibility safety perhaps NY does same with PCV for better emissions? Your RMV/DMV website should provide some info on same or at least a point of contact.
My PCV valve is due for replacement for the third time of owning my vehicle. When the dealer replaced the part the second time, I was told me the part was defective. Has anyone else experience the same issues? Doing research, I found that it’s uncommon for this part to go bad and need to be replaced. Is this part coved by state emissions law? I live in NY state.
 

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Discussion Starter · #3 ·
How long have you owned your vehicle and what model/model year? How many miles on same?

The PCV is a very heavy wear component. It's right up there with coolant thermostat & water pump and emissions O2 sensors. It's quite common for it to go bad in many vehicle use environments.

As such it's not warranty "covered" as it's a "wear & tear" item in most locations, but I can't speak for New York state emissions requirements. As some states freely cover windshield replacements for better visibility safety perhaps NY does same with PCV for better emissions? Your RMV/DMV website should provide some info on same or at least a point of contact.
Thank you for your response. My vehicle is 2015 GLA250 4 matic. The PCV valve was last replaced 2 years ago. My car is parked in the garage at night during the winter time. It was not a bad winter in the last two years. Is there any thing else that can cause this part to go bad? This will be the 3rd time replacing the part. Last replacement was two year ago? About 23,000 miles placed on vehicle within the two year time.
 

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The purpose of the PCV is to return unburned gases/oils from the internal combustion cycle to, hopefully, be re-burned and in turn reduce emissions. So anything related to said process can effect this valve on a continuing basis.
Therefore proper spark (were 'plugs replaced per maintenance schedule?), proper timing (pretty reliably computer controlled but perhaps in error), piston rings operating properly (shouldn't be an issue for a fairly new 2015), regular oil/filter changes, and not least of which is proper fuel (at least 91 octane of "Tier One" preferred, such as Shell and Mobil).
My point obviously is that many things related to the combustion process can wear the PCV and sometimes more readily than you might expect.
btw: Some enthusiasts install a "catch can" and repipe the PCV inlet to collect these gas/oil byproducts and thereby spare the PCV some of its work (I'm done so myself on a couple prior sports coupes, just because). Not advocating same for you but highlights that this has always been a heavy wear item.
Note: I've not had to change the PCV, nor the O2 sensors ... as yet ... in my 2018. I've probably just jinxed myself. :unsure: I add StaBil 360 marine to my fuel on a regular basis but that's more to stave off the rubberoid seal deleterious effects of my state-mandated 15% ethanol. 😖
 

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Discussion Starter · #5 ·
Thank you for response. All the recommendations have been met. All work was done by the Mercedes dealership.
 

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Good. What fuel have you routinely been using?

Two years is not very unusual, although somewhat atypical. Of course driving environment and style plays a part as well.

Also remember when you start up the vehicle head right out, keeping the acceleration gentle until the engine is warmed (coolant temp ok; oil temp better). Sitting and idling the vehicle to warm it up involves more rich fuel burning which can lead to more emissions byproducts and hence faster PCV & O2 sensor fouling.
Thank you for response. All the recommendations have been met. All work was done by the Mercedes dealership.
 

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Also remember when you start up the vehicle head right out, keeping the acceleration gentle until the engine is warmed (coolant temp ok; oil temp better). Sitting and idling the vehicle to warm it up involves more rich fuel burning which can lead to more emissions byproducts and hence faster PCV & O2 sensor fouling.
I was wondering if there are many short trips where it does not get up to full operating temp would cause the problem. Fuel being too rich.
 
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