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2012 ML350 and 2006 S430 Sedan
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Discussion Starter · #1 ·
I was tinkering with my car yesterday (trying to troubleshoot an intermittent cooling level light), and noticed a ticking noise that I hadn't heard before. I traced the source to an electrically-controlled air valve on the left side of the engine compartment next to the MCU. It appears to connect to the MAF header through a check valve. I'm not sure where the air goes after this valve or what it's purpose is.

Anyway it is making a ticking noise on cold start and then at random times after warming up. It seems as if the valve is opening/closing rapidly which I'm guessing is not proper operation.

I'd like to learn more and determine if this is correct behavior or not. However, I'm not even sure what this valve is called. Can anyone get me started?
 

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2001 SLK 320(222K Miles), 2002 E320 Special Edition(186K Miles)
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3,473 Posts
Your photograph is not very clear. However, if the object you are referring to has the letters MOT on it, then you are referring to the purge valve.

If it ticks, then it is working! It is used to burn off the fuel vapors which are collected in the fuel tank. It would normally tick more after start-up to burn off the fuel vapors collected while the car was standing, and then at random times as more vapors are collected.
 
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