Something missing from my air intake? - PeachParts Mercedes-Benz Forum

RML · #1 07-01-2007, 08:50 PM

I finally had some time to tinker around under the hood on my 84 300D this afternoon, so started by cleaning up some various oil spots around hoses. I took off the air intake assembly and noticed that there is a drainage hole on the right side at the low point, at about 8 o'clock, just back from the air intake. After I took the assembly off, I realized that this hole is the source of a significant amount of oil dripping onto various part below. Is there supposed to be a hose here, preventing the mess it is causing? Should it be recirculating back in somewhere?

lietuviai · #2 07-01-2007, 08:58 PM

Photos?
Are you talking about a small hole, maybe about 6mm in diameter or are you talking about the fitting that's underneath that should connect to a pipe that runs to the oil pan?

jim16671836 · #3 07-01-2007, 09:03 PM

You should have a tube that returns oil to the oil pan... Lift off the air cleaner and look... Jm

RML · #4 07-01-2007, 09:04 PM

It is the 6mm hole located outside the circumference of the filter. The fitting going to the tube that runs to the oil pan is OK. I lined that up when I put the assembly back on and it was lined up when I removed it.

lietuviai · #5 07-01-2007, 09:43 PM

I've seen that hole on all of those air cleaners. There isn't anything that goes to them. I'm assuming this is on your 84 300D with 309K. There could be something plugged up with the oil separator, increased blow-by or both.

RML · #6 07-01-2007, 10:12 PM

Yes, this is on my 84 300D with 309K. So from what you are saying, there should not be oil out at this point of the assembly, outiside the ring of the air filter.

I don't know if it had anything to do with it but I noticed that the plastic air duct going from the turbo unit up to the air intake was not connected tightly at the bottom turbo side. The gasket is rather hard and brittle and the last person who serviced it most likely was not able to get it firmly back on the turbo unit. It was difficult for me to get it on, and I will need to purchase a new gasket.

Magoo · #7 07-01-2007, 10:25 PM

There should be no oil dripping from the hole outside the ring of the air filter.
Replace those turbo tube seals ASAP. You're sucking dirty air thru them.

RML · #8 07-02-2007, 01:30 AM

Good point about sucking dirty air. I was able to get the fitting on with some difficulty and it is secure now. It looks to me like there is a K&N filter installed. I am thinking I will get an OEM paper filter and new air duct gaskets, clean up the air intake assembly and see how she runs. I am assuming that when I take the K&N filter out and clean eveything up, I will come across the oil separator. Is anyone aware of a diagram available for this air intake assembly? I did a search but did not come across one.

Many thanks for the valuable advise!!

Mister Byrnzoil · #9 07-02-2007, 07:26 AM

dont forget to replace the rubber air cleaner mounts too... I've got some if you need them.

RML · #10 07-02-2007, 12:23 PM

What is the telling point at which you decide to replace the rubber air cleaner mounts? They were not cracked or falling apart. I'll take a closer look to see if they are brittle.

1983/300CD · #11 07-02-2007, 12:44 PM

If you are not sucking air through the system as designed, you can have oily air build up inside the can. Keeping those gaskets in place is necessary to keep air flowing properly.

Also check the oil vapor separator for blockage. There is a hose running from the top of the valve cover to the top of the air cleaner box. That part inside the air cleaner can is the separator and where the vapor is (theoretically) separated into oil and air. The oil goes down and out to the crankcase, while the air goes to the intake.

SD Blue · #12 07-02-2007, 01:09 PM

Sealing around the top edge of the oil separator also helps considerably to cut down on oil in the intake area.

Mister Byrnzoil · #13 07-02-2007, 04:56 PM

Quote:

Originally Posted by RML

What is the telling point at which you decide to replace the rubber air cleaner mounts? They were not cracked or falling apart. I'll take a closer look to see if they are brittle.

My experience was that all 3 mounts had snapped, and I could lift the entire air cleaner assembly off its mounts

IMHO the air cleaner mounts are pitifully undersized and not at all an example of 'fine german engineering'.

anyway, I'd leave it alone if there is no undue rattling or movement of your air cleaner assembly.

toomany MBZ · #14 07-02-2007, 04:59 PM

Quote:

Originally Posted by RML

What is the telling point at which you decide to replace the rubber air cleaner mounts? They were not cracked or falling apart. I'll take a closer look to see if they are brittle.

Sometimes the nut on the inside of housing comes loose, sometimes the mounts loosen from bracket. If they are not broken, try tightening, no need to replace. Check bracket to see if that's broken.

RML · #15 07-03-2007, 09:17 PM

Thanks for all the input. I opened up the oil vapor seperator and everything is clean and clear in there. The hose from the valve cover is clear as well. My K&N filter was oil soaked so I gave it a bath in kerosene. I trust this has no ill effects. I wiped everything clean with kero and put it all back together. When I drove to work this morning I had a lot more power. I think I was choking the engine with a dirty air filter. Perhaps it was a recent sustained road trip that started this problem. I am going to keep an eye on any oil buildup in the air cleaner chamber and explore changing out the check valve. It also seems like the O rings at the top and bottom of the tube going down to the oil pan are worn thin. The tube fits very loosely into the hole below. It does not appear that this tube can be removed without taking off some other parts like the turbo unit so I am hoping I can replace the O ring from under the car.

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