300SD Oil Cooler Drain

[warmblood58]

For the past year, I have been draining my oil cooler when I change oil. You would be surprised how much drains overnight . . . about a 1.3 quarts! My lower oil cooler line is loosened and tightened just enough each time so that I do not damage the aluminum threads. It just seemed silly to me to add fresh clean oil to that much dirty oil (the oil in the oil cooler) in the system. Try it, you will be surprised!

[SD Blue]

Yes, the gunk seems to settle in the oil cooler. But as you said, extreme care needs to be taken with those oil cooler threads. I always clean, both the cooler and line nut threads, really well with brake cleaner and use a silicone assembly lube (Dow Corning 4) and hand tighten all the way.

[vstech]

do you rinse the cooler out with any cleaners? I have heard some flush out the cooler and lines with brake cleaner on each oil change... me? I just pull the plug and filter, put it back together, fill and go. that filter is pretty good.

[Brian Carlton]

Originally Posted by warmblood58

You would be surprised how much drains overnight . . . about a 1.3 quarts!

Being that I've done the SD at least four times now..........I can assure you that it's not 1.3 quarts.

The amount will fill a 13 oz. coffee can to about the 3/4 point. It's about 1.5 pints......at most.

If the cooler lines have never been removed before, you have to decide if its worth risking the threads on that $490 oil cooler to drain what little oil it holds.

To me, 1.5 pints is not worth that risk at all.

[SD Blue]

Originally Posted by vstech

do you rinse the cooler out with any cleaners? I have heard some flush out the cooler and lines with brake cleaner on each oil change... me? I just pull the plug and filter, put it back together, fill and go. that filter is pretty good.

Nope, In fact I usually don't completely remove the line to lessen the chance of cross-threading. I loosen the top and bottom line nut about 3-4 turns, a slight tug on the line to break the seal and the oil begins to flow. The following day, I re-tighten them first thing and remove my old age reminder (clothespin on the door handle) and continue with the rest of the oil and filter change.

[pawoSD]

Yeah, there's no way the cooler holds 1.3qts, the actual inside volume of the thing is pretty small. I remember when I replaced ours (I have done two) I got maybe a tin can full of oil....no where near a qt. And no way is it worth it to open it up each time.

[Hit Man X]

I am not worried about that little amount of oil when adding eight quarts fresh.

[warmblood58]

then perhaps you could explain how I manage to remove 1.3 qts each time I have done this? I know because I used a funnel and poured it back into a quart container. What I wish Mercedes would have done is provide a petcock or drain plug. I may, should I ever remove mine have this done by a competent shop, will report back to the forum on the outcome -

[pawoSD]

If the engineers at MB thought it was important to drain out that little bit of extra oil, they would have added a drain plug to the oil cooler. The early cars had it, then they probably realized how over over over kill that was, and got rid of it. I'm not too worried. I change my oil every 4k or so, and its made it this far....

[Hit Man X]

Originally Posted by pawoSD

I change my oil every 4k or so, and its made it this far....

My thoughts for the most part right there.

[Brian Carlton]

Originally Posted by warmblood58

then perhaps you could explain how I manage to remove 1.3 qts each time I have done this? I know because I used a funnel and poured it back into a quart container. What I wish Mercedes would have done is provide a petcock or drain plug. I may, should I ever remove mine have this done by a competent shop, will report back to the forum on the outcome -

Is the oil filter housing fully emptied when you perform this procedure?

[chetwesley]

He will probably respond himself, but from one post above, it sounded like he did this first, and then continued on to the rest of the oil change. This could explain the extra oil.

If you read the Chilton manual (DON'T!), it says to drain the cooler. Luckily, I didn't read that part until after I had done my first oil change, and I later learned about the dangers of messing with those lines.

[warmblood58]

I first pull the drain plug, then pull the filter from the housing and the last thing I do is disconnect the lower OC line - I still maintain why leave that much dirty oil in the engine when you do not need to - Mercedes engineering is good but they do not think of everything

[pawoSD]

Originally Posted by warmblood58

Mercedes engineering is good but they do not think of everything

Yes they do....cars before ours had a drain plug on the oil cooler. Later cars do not. So obviously they had thought of it, and later decided it was not necessary. (which its not)