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Old 08-03-2007, 12:28 AM
E150GT's Avatar
I'm a chicken
Join Date: Sep 2006
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weird question

I was driving tonight and I smelled crankcase oil in the cabin. I could also smell it outside the car too. I took the air cleaner off yesterday and I noticed a broken vacuum line to a hose that goes from the air cleaner bottom to the bak of one of the valve covers. I also noticed some oil in that tube connected to the air cleaner. Why is oil in there and how do I keep it out? Also what does that vaccum line go to? thanks for any replies

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Old 08-03-2007, 12:53 AM
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Location: Round Rock, TX
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I could be wrong, but I think what you are describing is the crankcase ventilation tube - the one that goes from the valve cover to the bottom of the air cleaner. Its purpose is to draw crankcase fumes into the air intake, so that they get burned through combustion, as opposed to simply being released to the atmosphere.

Since the idea is for intake vacuum to draw the fumes into the intake, oil vapor also gets drawn up the tube. This vapor can condense within the tube, but should drip back into the crankcase, if properly installed. Hence, the oil you found inside the tube. It is not uncommon for some oil to be found in the tube, but if you have a noticeable amount (say, teaspoons full), and then you may have something causing your crankcase pressure to rise abnormally - rings, etc.

If you smell oil fumes in the cabin and outside the car, you either have an oil leak or your crankcase ventilation system is not properly connected. Also, perhaps you dripped a little oil on the exhaust manifold yesterday.
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Old 08-03-2007, 11:14 AM
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Check the valve cover gaskets on your M116. They tend to work their way loose after a while, even with properly torqued bolts. When these gaskets seep, the oil lands right onto the exhaust manifolds and produces that characteristic "burnt oil" smell.
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Old 08-03-2007, 12:17 PM
david s poole
Join Date: Mar 2005
Location: dallas
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one more thing,you also have a hose from the other valve cover to the intake.where the hose goes to intake there is a small hole at bottom of pipe that has engine vacuum while running.these holes block up.take a large paper clip ,straighten out and clean hole.with engine running and hose off you should feel strong vacuum with your this will reduce pressure in crankcase and stop oil travelling thru the other pipe.
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Old 08-03-2007, 04:33 PM
E150GT's Avatar
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Join Date: Sep 2006
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Thanks for the replies. My valve cover gaskets have been needing to be replaced for a while, but this smell isn't really of burned oil, but it smells like the oil that is on the dipstick. I will look at it today. My girlfriend is gonna get mad though. I spend more time with my car than her. Good thing she likes german engineering like I do.

1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual
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