Hello,
New here and have a question - I do have a '08 E350 and the burnt oil smell when heating is driving me nuts. I did have some of the common oil leaks, but have fixed them all. There's is no visible oil on the outside of the engine. The under body covers are bone dry. Nothing points to a leak. However, when turning on the heater, it smells like burnt oil. It doesn't smell at all when running the AC.

Are there any other areas/reasons why it could smell like burnt oil? It does seem it is fluctuating in severity - just like a drop of oil falling ones in a while making it really smell strong before it gets a little better.....

Any pointers are appreciated.

Thanks.

Sebo

 

Hello
I had a similar issue with my 2008 e320 Blutec.

no oil leaks but the cabin would smell of burnt oil, when heat was turned on.

Fix:
the issue is with poorly seated Cabin filter housing.

the housing is held in place by hooks on top and a flap that is bolted along with the windshield washer tank.

it appears there are 2 side clips that snap in to hold the housing, these are missing in my unit. Presumably broken during one of the service to replace the filter.

instead of buying a new housing, i wedged in a wine bottle cork to push and hold cabin filter housing securely. The cork is placed between the housing and windshield fluid tank.

Now, The car with AC or Heat does not smell any more.

 

Do you have a picture of the side clips?

 

The circled part in Pic 1 is missing in my unit.
The unit is supposed to be installed from top amd pushed in until the side clips locks in. Note this is looking at the pics of a normal unit.

Here i noticed the smell goes away only if the cork is in the center of the housing, as shown in Pic 2, As this pushes in the unit uniformly and sealing all sides.

In my first attempt I had placed the cork to the left of the housing, and noticed that while it helped it did not get rid of the smell entirely.


p

 

One thing though, even w/o the cork the smell should not be coming in. Why?

You can see there is a seal all around the engine that should prevent any toxic gases to leak into the "cabin air breather"'; otherwise, passengers will be exposed to them and you know what next. It would be like being in a closed garage with the car ON.

I would check the seals are all in place, and they are not nicked, broken, out of position, etc.

 

Agree - the seals should keep any or all fumes away. The seals all look fine, i raised them to make sure they form a proper seal. Being the first owner I know the hood has in no way been compromised.
i have sniffed around the engine block but cannot smell the same anywhere.

There is a small leak from the oil pan noticeable after a long drives, but is mostly clean rest of the time. I have replaced the the dreaded engine oil-seal twice, once at 65K and again at 145K. ( luv the ride and the power… so was willing to fix it.. all said, this vehicle has been nothing but a white-elephant and we call it “EAGLES, in reference to their song Hotel California”)

Re the smell, I initially thought it may have something to do with the coolant-leak as the smell was pronounced with the heat turned on. Also, there were times when the smell was completely gone, and at other times its faint with the AC on but much stronger with Heat.

i see quite a few posting on this topic - I wonder how others have managed to fix this issue. Or if someone is willing to run a hvac stationary test with the cabin air filter removed.

 

Thanks for the photos @Jawa-Itano . I think I too am missing the side clips on my 08 but will double check tomorrow. The seal around the engine bay is intact but I also get this smell if I turn the heating on and always assumed it was dust on the heater core.

 

i hope its ok to recommend and share my my MB repair experience - if any of you live in Austin, TX, i would highly recommend Luxury Autoworks. Thomas the owner is wonderful and found him to be just as picky or more than the owner.

 

Im having same issue, there was a small leak from injector seal for a while but it got fixed. And a some smell still occurs.

exhaust pipe is ok, no leaks/soot to see on exhaust manifolds aswell. Injector seals seem to be all fine. No bigger oil leaks as under engine is no oil drips.
I tried air-purifier trough air intake after filter. 2times, also put new charcoal air filter. Still same issue of burnt oil /engine smell.

So now the next things to try is to do a engine bay wash as maybe old soot and oil is smelling when the engine is hot and vapourising them.
but a no brainer to me is how this smell is getting trough the hood seals…

 

Have look at the back of the engine for any of the cam plugs? There are 3 of them, 2 on one side, 1 on the other. They may drop a bit, and fall on top of the exhaust/cats

 

I had previously posted that the fix to the problem is incorrect seal on the air filter housing.

i noticed the above fix works only for cooling. However - this is not the case when heat is turned on.

im beginning to wonder if it the heater coil is the problem. Is the coil damaged ie is it perforated and leaking coolant?

 

In reference to the dirty engine bay as potential cause - this theory can be refuted. The engine bay was cleaned at the time i replaced the dreaded oil seal leak for the second time (?? Am too fond of the car to get rid of it, have owned this new from 08, currently at 149k mi)

the engine bay is clean as a whistle, no other oil leaks but still have the issue. This is why I suspect the heating element as the potential cause. Note during cooling cycles cabin air flow bypasses the heating element. While a complete seal is not assured this perhaps helps explain why there still is some faint odor in cooling cycles.

 

The darn issue resurfaced again!

looking more into it, found an oil leak at the region between the vacuum pump and engine block.

First instinct was to replace the $15 gasket that sits between the two. While removing the vacuum pump noticed the lower let bolt coming undone with little or no effort.

anyway, replaced the gasket and used new bolts. Fixed 95% of the leaks.

however, the fix to get the remainder has not been easy! Finally, several hrs later found my issue.
the pump housing does not sit flush against the block.

i can trace back the problem to one of the indie shops that came highly rated for their knowledge of diesel MBs, the first time i had opted to get the oil pan gasket fixed at a non dealer shop in 2012 - the biggest mistake in the life of this amazing car. Have Owned it new since 2008.

the idi..s have messed with the block - and for some reason used a circular sander across the entire surface of the engine block. They have messed up the flat surface and sanded more at the center - while the 4 sides fit snug the bottom center does not mate flush against the engine block.

used a 3000 grit paper and a hand held block to smoothen out to reduce the uneven surface. (Expand pic 1 and see the center line mismatch and the grooves)
2+ days of work, still couldnt get the surface to line up straight. But it appears the leak is approx 99.5% fixed. There seems like a sliver of a leak that accumulates over time.

for now using high temp silicone to fill the gap. Fingers x’d hope it will hold for some time or until i can get a mini/compact belt sander that can cover the entire area in one go.

comments welcome on the use of hi temp silicone to hold the oil from leaking.

And surprisingly - after the sanding, the engine idles smoother and quieter!! And at hwy speeds of 75+ the car handled like its stationary. I cannot hear the engine when stopped at lights.!!
My guess is the there was excess air into the engine block because of the poorly sealed surface. Providing a proper seal ensbles the right amt of pos pressue.

A/c or heat blows clean air no hint of any burnt oil -😀

 

Original surface - pinch tonsee the uneven surface. Path of the oil leak

After several hrs of sanding.

 

Not v clean application. Hope it holds.
Worry is the sustained exposure to high temperature.
Thoughts anyone?

 

On my 2004 W211 I found that a leaky valve cover gasket was leaking a bit of oil on the engine, which imparted the burned oil smell. Fixed the leaky gasket, problem solved.

 

Hello

fixed the lea k 100%. Made a Gasket using Garlock-9900, and sandwiched it between engine block and the original gasket. No leaks whatsoever, since installed and 150miles later.

however was wondering -



Does anyone know what is the purpose of hole circled in red.?