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2017 Metris with 130k miles M274. I was getting at the thermostat and alternator from the top and snapped some pics inside the head. Can anyone give me any good, bad or neutral news as to what I'm looking at. I hadn't done a compression or leakdown test as the vehicle has never had any noticable issues. Looks like the 3rd valve is getting hotter than the others or hanging open? They definitely need to be cleaned.. except the 8th one.. no idea on that one.
The drops of coolant are from me making a mess with the thermostat and the debris was on the manifold and will be vacuumed out.
Your No1 issue is not the dirty intake valves but the crankcase blow-by around the pistonsthat vaporize quarts of oil through your intake and into exhaust lambda + cats.
Get that taken care of.
Looks typical to me, for the mileage. That buildup is from oil getting past the PCV system. Not sure how your PVC is setup but I'd imagine it's basically the same as mine. Their problem is they have a seal inside that fails and lets oil get sucked into the intake, where it does exactly what you see in your pix. There will always be some oil getting by, it's just substantially worse when that seal fails. It only goes downhill from there so I wouldn't blow it off.
As far as why the carbon deposits vary, I would assume it's based on where the PCV dumps the oil in and where it goes from there. If I were to put $ on it I'd wager the clean valve is furthest from the PCV.
So I would check to see what kind of PCV you have, and replace it. Places like pelicanparts.com, nemigaparts.com, fcpeuro.com, mbparts.mbusa.com etc are good places and should show pictures of the PCV.
My last car had this PCV leak issue but I had very little interest in replacing it, so I made a filter to catch the oil. I posted about it in case there were others who might be interested. Based on that and other redneck fixes I've posted, it seems very few rednecks own Mercedes.... My filter did work very well and caught 100% of the oil, but it requires maintenance.
As for cleaning the carbon you have now, that's a tough one. There's all kinds of youtube vids on it, if you have the intake off like in your pix. If you don't want to take the intake off then rumor has it Methanol injection will clean them. Seems weird but some who have done it say it does in fact work.
Looks normal for the mileage. The brownish valve stems are just oil varnish from the PCV system, nothing to worry about. The third valve looking different is likely just the intake runner design causing uneven airflow, not a hot or hanging valve. The clean eighth one probably sees regular fuel wash from the direct injection spray pattern hitting that area, keeping it washed down. No obvious signs of burning, chipping, or cracking. If it runs smooth, no misfire codes, and doesn't burn oil, just leave it alone. Trying to clean them in place often causes more problems.
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