2016 Mercedes E350 trace of oil in vacuum lines

[The Artillerist]

Was replacing spark plugs on wife’s car and noticed traces of oil in 2 vacuum lines that I had to disconnect for the job. Anyone familiar with these cars/engine, what could be the cause?

1st vacuum line in question:

A close up photo:

2nd on that had traces of oil was at the back of the engine, driver side:

A close up foto:

 

[dumkid]

The first vacuum line seems to go to the throttle body, and the oil in it probably came from the pcv valve or intake manifold. The second vacuum line looks like it goes to a vacuum pump. Vacuum pumps are usually lubed with engine oil so if the fitting on the vacuum pump has some oil in it i wouldn't worry. Where does the other end of these vacuum lines go?

 

[loneryder]

Looks like pcv system.

 

[The Artillerist]

The first vacuum line seems to go to the throttle body, and the oil in it probably came from the pcv valve or intake manifold. The second vacuum line looks like it goes to a vacuum pump. Vacuum pumps are usually lubed with engine oil so if the fitting on the vacuum pump has some oil in it i wouldn't worry. Where does the other end of these vacuum lines go?

So the bottom of the intake manifold also had trace amounts of oil. Both vacuum lines with traces of oil feed into the manifold…

 

[Astro14]

The rear one is clearly a PCV Line from the oil separator. Front one looks quite Similar. You’re lookin at a PCV system.

 

[Astro14]

https://www.ecstuning.com/b-assembled-by-ecs-parts/oil-separator-pcv-emissions-service-kit/06h103495ekt5/

 

[The Artillerist]

https://www.ecstuning.com/b-assembled-by-ecs-parts/oil-separator-pcv-emissions-service-kit/06h103495ekt5/

Thanks. The link is for a VW 2.0 turbo engine though.

Are you familiar with 3.5L DI Mercedes engine? Is this a common issue with a one particular part (a valve or oil separator or something) being a more common culprit or is it more likely that there is a number of parts of the PCV that I need to troubleshoot and anyone could be the culprit?

 

[Astro14]

Thanks. The link is for a VW 2.0 turbo engine though.

Are you familiar with 3.5L DI Mercedes engine? Is this a common issue with a one particular part (a valve or oil separator or something) being a more common culprit or is it more likely that there is a number of parts of the PCV that I need to troubleshoot and anyone could be the culprit?

I am familiar with that engine. Thought I had the correct parts link for you. Sorry about that.

They’re PCV hoses. Oil is normal. If they’re no longer pliable, consider replacing them.

 

[The Artillerist]

I am familiar with that engine. Thought I had the correct parts link for you. Sorry about that.

They’re PCV hoses. Oil is normal. If they’re no longer pliable, consider replacing them.

So oil tracing in those 2 vacuum lines AND in the bottom of intake manifold is normal on these engines, I understood you correctly? Is it normal in the sense that “they all have it with no adverse effects” or normal as in “by design”?

My one and only experience is with Mercedes M119 engine from the early 90s. I’ve exercised with that engine aplenty. I changed out all PCV tubes on that one and did NOT see tracing of oil. But that engine is my only experience. I know nothing about the grade of PCV technology and how it works on this 3.5L DI engine.

Another thing, have you ever cleaned intake valves on this engine? This is what mine look like at 112,000 miles. I know that’s par for the course for the DI, but just generally curious if this looks in the ballpark of normal, pushing off your own experience? Appreciate your 2 cents!

 

[The Artillerist]

* kept calling PCV tunes vacuum lines even after been told they are PCV . Time to start pouring ice water over myself every morning and bich-slap myself through the day to stave off dementia

 

[Astro14]

I’ve have not cleaned the valves on one of these engines. I have a walnut blaster, which is probably the method I would try. Those look way dirtier than I would’ve expected given the age/miles of the car. Spark plugs implies about 100,000 miles, right?

How many miles on this?

 

[The Artillerist]

I’ve have not cleaned the valves on one of these engines. I have a walnut blaster, which is probably the method I would try. Those look way dirtier than I would’ve expected given the age/miles of the car. Spark plugs implies about 100,000 miles, right?

How many miles on this?

Spouse’s the 2nd owner of the car. Last time spark plugs were changed at 50 something thousand miles, under the first owner. IIRC, around 52, at a dealer. Currently car is at 112,xxx, so 60k on plugs.

This is what old plugs look like. Mildly unused to my neophyte eyes. I switched cars with wife this morning, wanted to see if there were drivability improvements, and surprisingly the car does have more pep with plugs and idles with less, so to speak, ruckus if you will too

 

[Astro14]

The iridium plugs on both my Mercedes have a 60,000 mile service interval. Old plugs look good when they come out, even gap as new (0.7mm) but new plugs run better. I suppose looks aren’t everything…

Also, good on ya’ for using OEM plugs. They’re indexed on this engine.

 

[The Artillerist]

I suppose looks aren’t everything…

Apparently! I was not expecting a drivability improvement from new plugs that are changed on time, so my, bordering-on-wow amazement at amelioration of the throttle response and acceleration, is not due to a confirmation bias

good on ya’ for using OEM plugs. They’re indexed on this engine

With very few exceptions, such as Elring for gaskets or Bosch or something with the star ground off, or some Lemforder parts, it’s original parts for my cars. Down to windshield wipers. I just enjoy the hobby this way

 

[andreigbs]

Looks like a well-wearing M276 to me and I've had a couple over the years. Some oil vapors that condense are normal in the PCV system. As long as you have no trouble codes the system is operating fine. The plastic parts like check valves and 90* elbows get brittle with time and from being under the hood where it's hot, so it's not a bad idea to replace things on a schedule. I'd say 120K miles is a good interval, probably time for a new drivebelt and tensioner around that time anyway.

She should give you many more years of reliable service based on how you're taking care of it.

 

[The Artillerist]

The plastic parts like check valves and 90* elbows get brittle with time and from being under the hood where it's hot, so it's not a bad idea to replace things on a schedule

Could you please clarify:

1. by the “elbows” you mean rubber tubes of various kind?
2. what schedule and for which check valves are you referring to?

I got my sea legs on an M119, but that is my sole, a bit overgrown with moss, mechanical experience.

I'd say 120K miles is a good interval, probably time for a new drivebelt and tensioner around that time anyway.

At 112 mi, drive belt looks pristine. No micro-cracks whatsoever on the grooved side . The tensioner on that M119 I just mentioned, was original and still proper at 150,000 miles and about 30 years of age. I understand replacing rubber tubes before they become totally petrified so that it becomes a pain to withdraw them, but what is the merit of replacing a tensioner prematurely? I’m not repressing your supposition, just attempting to discuss it to understand it better

She should give you many more years of reliable service based on how you're taking care of it.

yeah, an E-class is a rather durable good