A way to drain more oil during a 617 oil change?
 

I'm not really happy about the reality that about a quart of oil remains in the engine during an oil change. It's conceptually kind of like draining your oil then adding a quart of dirty oil back in. Most of the oil is trapped in the cooler and some people remove the lower cooler line to get that oil out, but that is fraught with problems, like stripped fittings, not to mention the mess.

So I got to thinking about how to conveniently get at that oil and get a better oil change.

So I came up with a conceptual strategy to use compressed air to push the oil out of the cooler back to the oil filter housing.

First, we need to look at the oil flow. It flows from the lower connector on the oil filter housing to the lower connection on the oil cooler, up through the cooler and then back to the upper connector on the oil filter housing.

http://www.peachparts.com/shopforum/...1&d=1376350050

My strategy was to reverse the flow (red arrows) through the oil cooler and installing a Shrader valve in the upper line.

http://www.peachparts.com/shopforum/...1&d=1376350143

Under these conditions applying 10-15 psi of air at the Shrader valve would push the dirty oil down through the oil cooler and back to the oil filter housing where it will drain into the sump and out the drain valve. We have to reverse the flow of oil, otherwise the air would just bubble through the oil and not push a whole lot out.

Downsides are the fact that adding a valve adds a potential point for leaks/failure. This could be ameliorated somewhat by using a steel cap over the valve as a safety. The strategy also requires going with aftermarket hoses like my steel braided AN hoses and brazing in a Shrader valve - not a big deal but a consideration.

The other downside is the reversed flow. I don't think this would be a problem, but I'm open to thoughts on this subject.

I won't be even considering acting on this idea until next time I pull the engine, but I'd like some feedback as to whether you think this would work and be worth the effort.

BUT, before hitting the "Submit New Thread" button, I realized that this just won't work. Rather than waste all the effort to create images and write up the idea, I thought it would be fun to see if anyone can identify why this strategy, while interesting, just won't work? And who knows, in the process might come up with another strategy that would work.

I think the air would just head into the housing instead I through the lines, path of least resistance. Plus I don't think you can truly use air to get all the oil out if it wasn't the case. I would rather put a drain plug on the bottom of cooler. That should remove most of the oil, but will still have some pooling in the lines.



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I think the air would blow out the oil... the oil thermostat should properly direct the air.

I don't know if it was the w115 or my euro but one of the cars I had....did have a drain plug on the oil cooler....I remember going to change my oil in my current car, and I was like hey I will just drain the cooler....but I was shocked when there wasn't a bolt...

That was my original thinking, but it turns out that the oil thermostat is on the bottom line, so any air pressure would just blow out into the housing body being effectively blocked by the thermo valve.


http://www.peachparts.com/shopforum/...1&d=1376361372

Your best bet would probably be to drill a hole into the bottom of the oil cooler and weld a nut into which you screw a drain plug in place.

-J

Umm, why are you concerned about oil which has already been filtered?

I agree with compu 85 that a bung in the bottom of the oil cooler would be easier. I just see no justification to complicate the already plagued OM617 oil cooling system. There is enough potential for leaks in the OEM designed system that adding another failure point for the purpose of draining a little more oil is not worth the effort. These engines have been running quite well for the better part of 30 years without draining that extra quart or so of used oil. I think that if it were that much of an issue, MB would have addressed it.

Up through the 115 Mercedes provided a drain on the cooler. After that they decided it was not important enough to do. If they think its ok, its ok with me.;)

Only un-filter Oil goes through the Oil Cooler.

I suppose if you were able to jack the Front of the Car up high enough you could do a better drain on the Oil Cooler.
However there might be another quart of dirty Oil in the Fuel Injection pump because there is always a pool of Oil in there as the drain port is at the top portion of the Bearing Retainer.
If you have an IP with the 17mm Plug on the side some of that Oil will drain out when you remove the Plug. Depending on what position the Governor Weights are at you could get something about the size of the Vacuum Tubing into the IP Governor through the Plug Hole and suck out the Oil.

In the tech Manual it list the amount of Oil needed for a normal Oil Change and the amount of Oil needed if you were filling an Engine that never had Oil in it. There is a one liter difference.
So there is always one liter of dirty oil left in Your Engine when You do an Oil Change.

The 60X oil cooler would be impossible to drain without a drain plug on it, it is mounted very low in front of the driver's side wheel. I had an Audi with a similar arrangement, and it's service info also stated that the oil in the cooler does not need to be changed.

-J

The oil thermostat opens only at around 95 degrees C according to the FSM. Now if the oil never reaches that temperature, because the engine isn't driven hard, does that mean the oil in the oil cooler can be very, very old?

i get that impression. also, how how is too hot to leave the engine dry? i wouldn't want to be too near 100 degree C engine oil, but if the temperature were past that threshold, would the valve blowing trick work then?

I wonder using vacuum on the dipstick tube drains the filter and the cooler. This is not inserting a suction tube into the dipstick tube (like the systems you buy), but putting a vacuum hose over the dipstick tube and the dipstick tube becomes the oil pickup. I made a setup like that and was amazed that not one drop of oil came out when I took the drain plug out to check how well it worked.

Next time I do a vacuum oil change I will check. It would seem given enough vacuum, that it would drain the filter and cooler if you plug the breather momentarily to create a stronger vacuum.

I don't think a standard bolt type drain plug would work very well with the 603 w126 cooler. Too much cooler movement from the rubber bushings that I would be afraid I might bend the how assembly removing that plug.
You'd have to go with a ball valve or something like that.

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