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1994 E320, 1993 300E
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364 Posts
Crankcase ventilation. There should also be a check valve that opens when the crankcase is under positive pressure.
 

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'92 W124 230E (Manual)
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136 Posts
Discussion Starter #3 (Edited)
Thanks. So should it be letting oil into the airfilter housing? Also there's some sponge on the undeside of the airfilter cover that is saturated with oil and the sponge is perished, there's tiny bit's of sponge coming off, if you run your finger over it, it just breaks down. This is within the "cleaned" airfilter area, surely not good for air intake going into the engine?
 

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1994 E320, 1993 300E
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364 Posts
The sponge should be replaced. It should not be coming apart. I am assuming that the sponge you are talking about is in some sort of holder that is attached to the hose. The idea is that the sponge collects the oil. the oils then runs back into the engine through the hose. There shouldn't be an excessive amount of oil in the airfilter housing, a small amount is okay but if there are standing puddles you defintely need to check it out.

There should be several hoses that connect the crankcase, the camshaft cover and the air intake, along one of these hoses you should find the pressure regulation valve. Check the valve, it should rattle when you shake it. If it doesn't, get a replacement.

Greg
 

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1990 300E
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450 Posts
Excessive oil in the filter housing (blowby) can be a sign of worn rings or valve guide/seal problems. Do a compression check.

Michael
 

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'07 GL320CDI
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5,112 Posts
You question the design and ask why there's a hose.

Your question should be what causes the oil.

It isn't just because there's a hose there it's because something's wrong with your engine.

Taking the hose off or plugging it, for example, isn't going to fix it.
 

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'92 W124 230E (Manual)
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136 Posts
Discussion Starter #7
lkchris said:
You question the design and ask why there's a hose.
Yes it's my first benz and the first time I've seen a hose coming from the engine into the air filter, so I wanted to know the logic behind it. I think it was answered, by GDC, it's for crankcase ventilation?

lkchris said:
Your question should be what causes the oil. It isn't just because there's a hose there it's because something's wrong with your engine.
Now we're getting somewhere and good thing I asked the question. So what in your learned opinion is wrong with the engine?

lkchris said:
Taking the hose off or plugging it, for example, isn't going to fix it.
Can't say this is what I did or plan to do, but thanks for the advice all the same.

I think I'll have a look into Michaels advice and do a compression check. I'll post back later with results.
 

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300-SEL, 300-E
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241 Posts
A compression check might be a good idea at this point.

Some (a little) oil in that line isn't necessarily horrible. But excessive oil in that hose is a good indication of excessive blow by from worn rings.

One quick, easy test is to disconnect that hose from the valve cover with the engine running. It shouldn't blow much out of that hole. If it's blowing smoke rings or looks like an old steam locomotive blowing out that hole, you have a problem (probably rings). You can also pull the dipstick with the engine running and see if it blows any smoke or oil out the dipstick tube. An engine that blows smoke rings out the dipstick tube also has a problem (worn rings or worn cylinder bores).

If you have some blowby, but it's not horrible, you can try an engine treatment called "Restore." I've seen some good results with that stuff in the past. It's worth a try (about $7 to $10 per can IIRC). I've used it as a last resort when I was fully prepared to do an engine rebuild, but needed a little more time before getting to the work. One engine cleared up enough that I didn't bother with the rebuild. YMMV.
 

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1994 E320, 1993 300E
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If Restore is not available in in your area, there is another product called Engine Honey that may be. Honey is exactly what this stuff looks like. This material is shear thickening so it flows and pumps easily, but firms up under high shear like that associated with piston rings sliding along the cylinder wall. This is how it reduces blowand oil consumption by in worn engines. When the shear is removed, the stuff simply flows back into the pan to get recirculated. I used it during my college years when I didn't have the money to rebuild the engine in my old F100.

Greg
 

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'92 W124 230E (Manual)
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136 Posts
Discussion Starter #10
Thanks, there's no smoke rings coming from the dip stick and the car runs fine otherwise, I guess the amount of oil is pretty small, but something I have to watch. We have a formula called Wynns Stop Smoke, I used it in my lawn mower recently and it certainly did what it claims to do.
 

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1989 W124 260E
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1,783 Posts
STV3E Remove valve cover and clean out oil drip tube along the top of the engine cam and lifters .Also clean the small holes in the valve cover Re fit with new Mercedes gasket torque down to 9 nm . Do a engine flush first to clean out the crap inside the engine ,,use a good flushing additive ,fit a new filter and oil. Look in to Liqi Moly engine oil for the older type engines.
 
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