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It's been broadly noted that the oil in some MB engines cannot be completely changed using the Mighty Vac system. In my case with an M276 engine in a 2015 GLK350 4matic, the Mighty Vac seems to leave about 1.5 quarts behind. The dipstick tube seems to get stuck before it reaches the bottom of the oil pan and a significant amount of oil won't come out.
I've posted that I'd reached out to the parent company for the device (Lincoln) and they made a couple suggestions. That post is here:
Well, my time for an oil change has come around and... it works!
The Mighty Vac ships with a larger ID "suction tube" and two smaller ID "dipstick tubes". The "dipstick tubes" each use an adapter that creates a seal on the "suction tube". One end of each adapter has a larger ID (I'll call this "open") for the suction tube and the other end is smaller (which I'll call closed) for the dipstick tube. We're going to use both adapters on ONE dipstick tube. To avoid confusion, I'm going to refer to the hole in the engine that we're going to stuff this into as the "dipstick receiver".
There are two dipstick tubes provided with the Mighty Vac. Attach the "larger" dipstick tube to the suction tube just like normal. Now take the adapter off the smaller dipstick tube, reverse the orientation vs the first adapter and slip it on the larger dipstick tube. Position it on the tube so that the tube will go about as deep as the dipstick. (This distance probably isn't terribly important - that was just before it bottomed out for me.) The "trick" is to stuff the "open" end of the adapter into the top of the dipstick receiver to create a vacuum seal. The closed end will create a seal on the dipstick tube above the dipstick reciever. You should find that the open end is somewhat flexible, and, in the photo below, it seems like it has a stepped taper. (Almost like it was planned?!) I was able to stuff the first step down into the dipstick receiver to create a seal.
Note stepped tapering.
The extraction process went much like normal with much noise and gurgling when it was done.
How did it work? I was able to quickly remove what seemed like most of the oil - and then opened the drain on the bottom of the crankcase. I let the oil drain from there for several minutes and collected less than 8 ounces of oil. This suggests that about 6.6 out of 6.9 quarts was suctioned out. That's a bit better than 95% removal. My bet is that this exactly what happens in the shop! Considering the hassle of getting the ramps, putting the car on ramps, removing the lower shield etc - and that I always change my oil well before the allowed interval, I'll take the time savings and run with it!
My current understanding is that the dipstick receiver can be viewed as a steel tube that extends from the engine compartment, probably with either bends or tapers to very near the bottom of the crankcase. When we pull a vacuum on the dipstick receiver, the oil will flow into the dipstick receiver, through the tubing we've inserted and we can capture it in the Mighty Vac. Without doing this approach, we can't reach the bottom of the crankcase - and we can't make a seal further down the dipstick receiver with the hard plastic of the dipstick tubes. Using this approach, we are getting the vast majority of the oil out of the engine.
That's what i noticed too from the video in the prior post and what drove me to look further. I actually inquired about getting the fittings used on the other machine, but the folks at Lincoln/MightyVac redirected me to try this approach.
As stated, the amount of dipstick tube down the receiver hole probably isn't really important. I felt that the coupling at the top was likely to loosen up as soon as I had lost the solid flow of oil into the Mighty Vac, so keeping any oil splash from the vacuuming process down away from where it could escape the engine wouldn't hurt. That's why I put the tube down low in the receiver.
Bottom line for me, I can do a top-side oil change at home again!!
03-22-2019, 03:08 PM
