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Replacing the Oil Separator Check Valve

on the 1981 300SD (OM617)

by dmorrison


617 engine, replacing the oil separator check valve in the upper oil pan.

As discussed in this post, my car has an annoying leak near the turbo and oil separator drain tubes.
I replaced the turbo drain tube grommets and gaskets in this post.

I replaced the O rings in the oil separator drain tube and still had the leak.
My theory is that the check valve was remaining open allowing oil to be sucked up the drain tube, OR the valve was stuck closed and not allowing the oil in the tube to drain after engine shutdown. With the engine running I'm sure that there is always a vacuum, caused by the turbo, in the oil separator/drain tube area. To prevent the oil in the oil pan from being sucked up into the air filter assembly, the check valve shuts off the oil pan air going into the drain tube. Then all the air/oil from the PCV tube going into the oil separator accumulates in the cyclone bowl and drains down the tube. When the engine is shut off the check valve in the upper oil pan opens and allows the accumulated oil to drain. At least this is what I have concluded. Is this the way the system works?? Not 100% sure but the theory seems logical. If anyone else has a better idea please speak up.

Parts needed:
1. A new check valve.
2. A new holding sleeve.
3. A new lower oil pan gasket.
4. 8 quarts of oil.
5. A new oil drain plug washer
6. A new filter if you want to do this.

Torques for the bolts:
Drain plug 35-45 Nm (25-33 Ft Lbs)
Oil pan bolts 9-11 Nm (6-8 Ft Lbs 79-97 Inch Lb )

Photo #1. Is the oil separator setup in the 617 engine. Item number 7 is the check valve and the drain tube is highlighted in red.

Photo #2. This is the problem. The result of what I think is a failure of the check valve to operate correctly. After removing the check valve I found it to operate poorly and intermittently.

Photo #3. Another view of the area where the oil is leaking

Photo #4. These are the tools I used doing the job.

A. Lots of shop rags. The oil pump will continue to drip while the oil pan is off, annoying and messy
B. A inch Pound torque wrench to tighten the oil pan bolts. Attached to it are a 1/4 drive extension and a 5MM allen head socket.
C. A paint scrapper to completely clean the upper oil pan matting surface for the power oil pan.
D. Pliers to remove the holding sleeve.
E. A 5MM allen T wrench to remove the oil pan bolts.
F. A 10MM socket set and extension to remove the air filter assembly.
G. A 13MM box wrench to remove the oil drain plug
H. Lots of degreaser.
I. A brass punch to drive the holding sleeve into the upper oil pan.
J. A hammer to, well you know what a hammer is for!!

Photo #5. These are the 2 parts that you should buy to do the job. The new check valve to the left and a new holding sleeve on the right. The check valve looks a lot like the vacuum pump check valve. I would recommend a new holding sleeve. The old one might not spring back correctly when removing and you don't want to go back in there to fix that.

Photo #6. Now to get to work. I removed the air filter assembly so I could clean the drain tube out. I did not take a picture of that. This picture shows the car on 2 sturdy jack stand and you need to drain the oil. Once you remove the oil pan the engine, oil will continue to drip. Lots of rags and you will get oil on yourself.

Photo #7. This is the lower oil pan . Use a 5MM allen wrench setup to remove all the allen head bolts holding the oil pan. The oil pan is light and 1 allen head bolt will hold it in position but make sure you don't bend or twist it. There will be an ounce of oil in the bottom of the pan when removing it.

Photo #8. 4 bolts are of a different length and should be kept track of. This, out of focus, picture shows the driver side transmission cooler line holding bracket. This bolt is longer that the others. Also on the transmission cooler lines are 2 spacers, don't forget these.

Photo #9. On the passengers side of the engine are the 3 other bolts that should be kept track of. The other transmission cooling line holding bolt ( and spacer) and the 2 bolts that hold the AC high pressure hose in position on the upper oil pan area. The AC hose bolts also have nuts that do the actual AC hose hold down. The 2 bolts that hold the oil cooler lines are longer that the AC hose bolts.

Photo #10. The culprit. The opening on the top that has the sleeve and check valve is the oil separator drain tube unit. The other large opening is the turbo oil drain line tube. Notice the amount of sludge in the check valve.

Photo #11. To remove the holding sleeve just use some standard pliers and squeeze the holding clamp so that it can be pulled out. I then sprayed degreaser down the drain tube to make sure nothing was blocking it. After it drained I blew air though it for a while to completely evaporate the degreaser.

Photo #12. Here is the new check valve and holding sleeve installed. To install it. The nipple on the check valve MUST BE DOWN. While holding the clamping sleeve with your pliers place the check valve on the sleeve with the check valve nipple down. Position the combination in the hole and press it in. The clamping sleeve has a beveled edge and a non beveled edge. I placed the beveled edge at the top to assist in inserting the sleeve. I could only get the sleeve started using the pliers. I then drove the combination all the way using the brass punch and the hammer. Tap it lightly this is not a wheel bearing or such. You will know when it is seated by the change in sound while tapping as well as it not moving any further. Note the amount of exposed sleeve in the pictures.

Photo # 13. All the parts have been cleaned and are gathered together to reassemble. Notice the new oil pan gasket. Make sure you completely remove all of the old gasket from the matting surface. Photo # 12 shows the clean surface of the upper oil pan.

Photo # 14. The completely assembled oil pan with new gasket and check valve. I now have to degrease and pressure wash the engine and under carriage. This leak has made a mess.

Photo # 15. My personal reward.

The part number is 617-018-00-29 Check valve. Make sure it comes up as check valve.

It has now been a couple of weeks and driving the car has produced no oil leaks from this area. Lets not talk about the other leaks. So this was the cause of the leak around the upper oil pan area.

Discuss this DIY here.


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