1986 300SDL & oil removal

Hello folks. I'm having a little problem extracting most of the oil out of my newly acquired '86 300SDL via dipstick. I'm using a Topsider that I've had no problems using on my other car, an '85 300D. The Topsider's got vacuum and works as it should. I'm only getting roughly 6 liters out of the SDL. I have both the oil filter and oil filler caps unseated. The car, warmed to operating temps, is parked on a slight slope with nose downwards. I'm wondering if either the oil pan's construction or the dipstick tube is preventing the Topsider from doing a better job. Any help is appreciated.

I bit the bullet and bought a Portaquick 12V oil change pump from West Marine. I put the back of the car up onto small ramps, ran the engine for about 5mins, let the car sit for 10-15mins, then I let the Portaquick suck away. It does a nice quick job and this time I believe I got most, if not all, of the old oil outta the pan. I took the car off the ramps and onto level ground. I put 7.6 liters (two of the gallon Delo 400 bottles) into the car and checked the stick. I was surprised to see it registered maximum. The owner's manual calls for 8 liters with oil filter change, which was done. Comments or suggestions?

[Hatterasguy]

I think MB changed the oil capacity on these in the early 90's to 7.5 quarts. However I just changed my oil last week and added 8 quarts and it was only 1/3 the way up the dipstick.

[ericnguyen]

Tony:

About 0.5 - 1 quart of old dirty oil always stays in the oil cooler and its connecting lines. Therefore, You can never remove all the old oil unless you have too much time to burn by draining the oil cooler/lines (big trouble if you mess it up).

Eric

Thanks Eric. I didn't think of that, and the manual stating 8 liters w/filter change threw me off. Guess I'm good to go.

[BobK]

If I was using a topsider, I would probably put the car dead level. i figure that is how MB intended the mechanics to have the car when they did oil changes.

The problem is that the engine is angled nose-up about 15-20degrees. It is not perfectly parallel to the road. Using the small ramps may have been overkill and I may try it next time on a slope without them. Either way, the Portaquick beats the Topsider for actual performance, but the Topsider facilitates easier used oil disposal.

[ericnguyen]

Tony: Of course, you're good to go buddy!

BobK: Mercedes never intended us to use Topsider-stype devices (with plastic tubes) to suck oil from the bottom of the oil sump. The real machine that MB mechanics use to remove old engine oil does not use plastic tubes. They just attach it to the oil dipstick tube at the top, and the machine will generate a strong vacuum to pull up old engine oil directly (no plastic tube inserted.)

For DIY topsider-stype devices, they cannot generate strong enough vacuum to pull up oil directly. Therefore, they have to resort to plastic tubes inserted through the oil dipstick tube so that they can touch the bottom of an oil sump and be immersed in oil. I observed that I could always suck a little bit more dirty oil by lifting up the car's rear. The junction between the oil dipstick tube and the oil sump is located near the left front of the oil sump, so it's easy to understand that more oil can be sucked out if a car's rear is lifted up.

When changing oil, I simply back up my car on a slightly sloped driveway and I'm good to go. Changing oil is a 5 minute biz for me since I started driving Mercedes at the beginning of 2003. Before that, I drove some old Honda, for which changing oil is a major pain due to oil filter location. I did try a topsider-stype device on my Honda but it did not suck oil very well because it's impossible to push the plastic tube all the way to the oil sump's bottom.

Last but not least, I can assure you that you can always remove more old dirty oil by using the topsider method in lieu of draining it through the drain plug thanks to gravity. The position and shape of the area surrounding the oil drain plug (inside the oil sump) prevents a somewhat decent amount of old dirty oil from escaping the drain plug.)

Eric