W123 Over-enthusiasm? - Learn from my mistake... - Page 2 - PeachParts Mercedes-Benz Forum

FrankM · #16 11-20-2011, 11:53 PM

I will ditto the vacuum pump as the culprit.

Not valve seals for sure.

Zacharias · #17 11-21-2011, 03:56 PM

If you want personal experience on how much oil can be burned off due to bad rings without resulting in objectionable smoke, I can assist.

I ran an OM617 to the point where it was drinking a litre of oil every day.

Just for context, when it was drinking a litre three days (maybe 75 miles of driving) even my mechanic didn't believe it was burning that much. It sounded okay, not great but okay and it took quite a while for it to smoke badly if left idling. I could still get away with using the drive-thru as long as no one made a $50 order ahead of me....

By the time I was down to a litre a day it was smoking very badly at startup and when cold and it was noticeable all the time when warm. Before I became a really gross polluter I basically lost one cylinder and just threw in the towel at that point.

But I agree that what the OP is talking about isn't possible via poor combustion. It has to be leaking somewhere when driving.

What does the underside of your car look like? Any drips from the oil cooler lines?

supercub · #18 11-21-2011, 08:06 PM

Sounds like someone is draining off your oil at night. Expensive it is nowadays, oil changes used be phrased as "cheap maintenance".
I notice on my 300D, and alot of other people too, that filling up to the top line on the stick will cause it to burn oil down until the level is about on the low mark.

RallyRebel · #19 11-21-2011, 10:40 PM

Thanks for the feedback all! And I assure you, no one is siphoning off my oil!

I'm not sure which vacuum pump I've got on this '81, I'll post a pic soon, but there's only the one line to the brake booster. I've disconnected ALL lines except shutoff as there's a leak in the system. But here's something that may be important: After starting the car, whether warm or cold, the idle will drop noticeably when I release the parking brake. I've never noticed this in either my NA 300D or turbo 300D. Indicative of a pump problem?

The car does smoke and it's consistent white with a little heavier volume at accelerating shifts. Sometimes I get the impression it "puffs" when going over speed bumps but it could just be I can it better as the mirror angle changes over the hump.

For what it's worth here's a video shot the other day of it idling, you can sort of see the smoke but the background hides it more than shows it: 1981 240D Idling

As for intake ingestion please keep in mind I ran it for about 50 miles with the breather tube disconnected and blocked off, the valve cover fitting covered with a K&N breather filter. It still went through almost 2 quarts of oil.

Since I've owned the car I've used Rotella 15W40 until this week as I got three gallons of Delvac 1300 15W40 since it was on sale. The car doesn't leak enough to mark it's territory but has a typical greasy belly, but nothing enough to drip. Most of what it has now is the result of me forgetting to pull vacuum on the rack during one of the compression tests!

As soon as I get my differential compression gauge back I'll get new compression numbers, both straight and differential. It sounds a bit better after adjusting valves the proper way.

leathermang · #20 11-21-2011, 11:24 PM

There are lots of threads and people who report that if they keep the oil level above half way between low and high on the stick ( and make sure you have the proper color dipstick ) that oil usage will be much higher.... that includes mine....

RallyRebel · #21 11-21-2011, 11:34 PM

Yeah, I typically fill between the notches and have the red dipstick.

TheDon · #22 11-21-2011, 11:36 PM

Quote:

Originally Posted by Rick Miley

Now that you've gotten your feet wet in the W123 world and learned a bunch of lessons, you need to upgrade to a better car. I know where you can pick up a Euro 300D with manual everything in pretty good condition.

oh really, do tell.. I may be interested....

leathermang · #23 11-22-2011, 12:58 AM

Rick has the ideal car design.... NA 5 cylinder , manual shift.
Its name is ' Granny Smith' ..... can you guess its color ?

Zacharias · #24 11-22-2011, 11:02 AM

Quote:

Originally Posted by RallyRebel

For what it's worth here's a video shot the other day of it idling, you can sort of see the smoke but the background hides it more than shows it: 1981 240D Idling

If you were selling that car, and I didn't know about the oil issue we're now discussing, I'd buy it in a heartbeat.

It sounds great, seems to run evenly (though the idle is higher than where I would set it) and, even assuming the background in the video is masking some of the exhaust, that's not smoking by my definition.

RallyRebel · #25 11-22-2011, 09:42 PM

Well I did the unthinkable. I've stooped to the level of using snake oil and put some Lucas Oil Stabilizer in. Now my reasoning is simply to use it as a thickening agent to help determine what's going on with this oil consumption, and it has reduced the level of smoking and slowed consumption to a little better than half the previous level. I don't like this stuff at all but it's not going to hurt anything using it short-term like this. I'm thinking to try some diesel-rated 20W50 after I run out of the current gallon of 15W40 and the Lucas to see if that helps. Worst case scenario just to keep driving I could go the Mobil-1 gear lube route! That'd be an interesting smell for whoever was following me.

I'm curious about the dipstick though. Is there a reference indentifying the lengths and positions of notches for various OM616 and 617 dipsticks? I've started to wonder if mine's too short and I'm overfilling, then again on longer drives I check the oil level when I see oil pressure drop on sweeping turns so I know it's still using oil enough to allow windage to uncover the sump funnel.

Here's a question for those of you thinking it's the vacuum pump: How is the oil getting from the vacuum pump into the exhaust? I've got the later pump with a single line to the brake booster with the only other thing currently connected being the rack shutoff. I don't understand how that could be evacuating oil out of the engine.

And again, no leaks or dribbles. Just a faint fog from the tailpipe and an otherwise wonderful driving experience coupled with mechanical mystery. Still thinking rings...

ADDENDUM: For those interested here's a link to my smugmug gallery of this car: 1981 Mercedes 240D

Orv · #26 11-23-2011, 03:51 PM

Find it amazing that you could be burning that much without the engine running away. I'm starting to wonder if there's any way you could be leaking oil into one of the exhaust ports via a crack in the head or something.

To lose oil that fast it almost has to be coming from somewhere pressurized.

EDIT: If you get really ambitious it would be interesting to pull the exhaust manifold and see if one port is especially coked up. That would tell you if one particular cylinder is the problem.

47dodge · #27 11-23-2011, 09:29 PM

at least on a 77, which is what I have the vacuum exhaust line goes to the air cleaner, so oil from it will go into the air cleaner also. makes an oily mess, and gets sucked into the intake. If yours does not go into the air cleaner or intake in any way then it can not be the problem. Then rings may well be it.

barry123400 · #28 11-23-2011, 10:08 PM

I read your compression numbers. In theory you could have that much general oil usage and destroyed oil control rings. I just suspect your compression rings would not still be that good. Remember your first compression readings where over 400 pounds before you adjusted the valves and tightened them down too much.

Figure out a way to find out if the head gasket is comprimised in the pressure feed to the head area. Thus dumping oil into a particular cylinder. Run the engine with the injector of the cylinder closest to the oil passage removed. If it spits oil out you have your proof.

Actually I would expect the injector of that cylinder to look pretty different than any others as well. If bad enough that also is a reasonable indication of proof as well. It just does not prove where the oil is coming from as running with the injector out. This engine with those compression numbers does not sound generally worn out to me. Many other members have little more than half the compression you posted and are motoring around.

RallyRebel · #29 11-24-2011, 07:39 PM

With the year's worth of WVO use the car had prior to me had me thinking oil control rings as well, but almost a year of soaking with MMO didn't seem to do much if that's case. Either way I don't believe at this point there's a simple fix short of inspecting the cylinders. I'm taking the following list of options:

1: Replace the 240 with either a euro 300 or turbo 300td, both of which I'll be looking at in the next few days. Then sell 240.

2: Re-assess body condition of my stick-shift 300 turbo and just go back to that mess.

3: Re-engine 240 with either NA 300 engine or stick-shift turbo drivetrain.

4: Go back to the world of the W116 and put my '80 300SD on the road.

It always boils down to time and money, time and money...

barry123400 · #30 11-24-2011, 11:22 PM

Unresponsible wvo usage can on occassion also score the cylinder walls. Again your compression still seems too high for this senario.

For the small effort involved locate the cylinder closest to that pressurized oil passage and check it out. This is not throwing money at it and very little time.

I doubt it is the reason but it should be eiminated as a possibility. Are you getting raw oil at the tailpipe?