300SD Oil Burning (Turbo Seals? Rings? Valve stems?)

[bustedbenz]

I apologize for yet another novel-length post. I understand this aggravates people. But I feel like it's useless to ask for people's time unless you thoroughly explain the situation to the best of your ability. If I shortened it, details would be lost that might be the subtle nuances needed to solve the problem.

Last week, we finally put license and insurance on the '82 300SD so it's road-test legal now. When I bought it (purchased from family friends, and worth what I paid for it in spite of these problems, so there's no need to go into the "did the seller tell you", etc part of it) -- they told me (and I think genuinely believed) that it only really needed 1 quart of oil in between changes.

Well.

I drove it to Boone and back yesterday (100 miles each way), making the trip I needed to make and testing the car simultaneously. Had a cloud of smoke following me most of the way which must have been oil. It was honestly hard to tell WHAT color it was (oil = blue, diesel = black, coolant = white as far as I know) but it seemed to be blueish/black. In hindsight, it MUST have been oil. So this trip was 100 miles one way. When I got there, I checked the oil. Before I left the house (checked immediately before I departed) it was just a millimeter or two (trivial over-fill; let's please save the foaming-oil-runaway-catastrophe debate for another thread unless it's REALLY part of my problem) above the full notch on the dipstick. After 100 miles, it was down to about a millimeter above the very BOTTOM of the stick. That's right... not above the low notch. Above the bottom end of the dipstick.

Never lost pressure and no funny noises, but... that could have been BAD. I never ran it dry, fortunately.

It took 3 quarts to bring it back up to a level in between the notches. Probably 7/8 of the way to the top notch.

Drove it home. Another 100 miles. Down to the very bottom of the stick again but maybe not QUITE as low as the last time. I should mention that the first 100 miles included an 8% grade for about 2-3 miles, which was the time at which it smoked the most intensely (Cloud was lingering behind me on every curve) and the engine worked the hardest. It makes sense that the return trip, which was nice and easy and mostly downhill, used SLIGHTLY less oil because the engine wasn't really working as hard.

The engine has 160,000 miles on it. Here's the clincher. I have a receipt in the glove box for a "300SD Turbo" -- as in replacing the turbo -- from 02/10/2010. 8 months ago, the turbo was replaced. I do not know if it was new or used, and I do not know what went wrong with the original turbo. I am going to get answers to both of those questions later today hopefully. However, the part was $300.00 if that helps. If somebody knows that a new one would cost $700 or something, then that proves it's likely a used replacement. I'm going to ask him as soon as I post this.

So... I'm really lost as to where it could be going. My understanding is that there are (not counting leaks) 3 ways to BURN, not leak, oil through an engine.

1) Worn piston rings
2) Worn valve stem seals
3) Failed turbo bearing seals letting oil blow through the intake.

1. Piston rings... is it POSSIBLE for an engine with only 160,000 (known true) miles to have worn out rings? I know a gas engine would be worn out by then, but I thought the whole reason so many of us are at 200,300k was that these didn't wear THAT quickly. What test would I perform to determine if this is a problem? I will have an opportunity to do a compression test around Thanksgiving. Probably illuminating either way.

2. Stem seals... they couldn't possibly burn 3 quarts in 100 miles over 2 hours, could they? To say nothing of more like 5 quarts in 200 miles taking the round trip into account.

I don't really see the kind of smoke on cold start that you would expect from valve stem seals letting oil leak down into the cylinders overnight. In fact, it only really demonstrates oil smoke when you're under acceleration or interstate speed. The rest of the time it just has the little bit of smoke that a diesel always has. The harder the engine runs, the more it smokes.

Finally -- the air cleaner center was very oily when I looked in there after I got home. I took the cap off the filter and the center section (the hub around which the filter sits) was black and wet. That must be where SOME of it is going.

So... the first question is -- what is the likely cause of this EXTREME oil burning? If it's the turbo, what tests or observations can I make (without dismantling the entire exhaust and turbo to remove it from the car) to see if removal is warranted?

And incidentally -- my 1986 300SDL has a BLACK oil dipstick finger handle. The 1982 240D has a RED one, and the 1982 300SD has a WHITE one. Are these all correct dipsticks for the engines? I can imagine a previous owner replacing it wrong or something. I wouldn't want to be measuring with the wrong instrument when the problem is this severe.

[kerry]

There is at least one other way oil can get into the combustion chamber--thru the PCV hose. Not saying that this is what happened, just that it is possible. I had an Austin Healey Sprite that was consuming gallons of oil that way.
My bet would be on the turbo.

[Marvelicious]

I've got similar problems, if not quite so bad. My intention is to:

A: give it the marvel mystery oil soak (loosen the carbon on the rings to lessen blow by)

B: rebuild my oil separator in the air box. Anyone got a good thread on this? Every time I search, I wind up finding people mentioning it, but no one describing the process. If there isn't a write up on it, maybe I'll have to do one. We'll see.

[Brian Carlton]

Originally Posted by bustedbenz

The rest of the time it just has the little bit of smoke that a diesel always has. The harder the engine runs, the more it smokes.

You failed to note the possibility of worn valve guides in conjunction with the seals. The guides would leak oil continuously, unrelated to load.

Therefore, if the oil consumption is much greater under high airflow (not necessarily high load), the culprit is the turbo seals.

You can verify this by revving it up to 3000 rpm in the driveway. If it smokes badly, similar to the situation on the highway (actually should be worse because the vehicle is stationary), you found your issue.

[bustedbenz]

Originally Posted by Brian Carlton

You failed to note the possibility of worn valve guides in conjunction with the seals. The guides would leak oil continuously, unrelated to load.

Therefore, if the oil consumption is much greater under high airflow (not necessarily high load), the culprit is the turbo seals.

You can verify this by revving it up to 3000 rpm in the driveway. If it smokes badly, similar to the situation on the highway (actually should be worse because the vehicle is stationary), you found your issue.

I'm not at home at the moment (college) so I can't do this stuff in person but I got my dad to do the 3k-rpm stationary test and when he did it, He could NOT get a cloud of smoke out the back. The smoke while I was driving it on that trip seemed intermittant.... there would be a cloud for a few miles and then not as noticable for a little while. I couldn't find any pattern so I'm assuming it just was a difference in my speed or engine load that I didn't readily observe.

In any case... we're still going to try to visually look down at the turbo and see if there's a puddle of oil in it the next chance we get, and I'm reading threads now on the oil separator. I'm wondering if perhaps the check valve at the bottom of the separation mechanism is plugged or stuck, and so the oil that normally would recirculate into the engine is instead burning.

Somebody in another thread mentioned that the vacuum pump could fail and let oil into the air cleaner that way. The air box IS oily, so I'm going to try to read up on that too.

I want to thank everybody for their patience in letting me ask questions about cars I can't do hands-on tests on except every few weekends and then report back and re-visit old issues when I'm finally dealing with them in person.

[Brian Carlton]

Originally Posted by bustedbenz

I'm not at home at the moment (college) so I can't do this stuff in person but I got my dad to do the 3k-rpm stationary test and when he did it, He could NOT get a cloud of smoke out the back.

Test definitely points to a culprit other than the turbo............something intermittent and/or load related.

[bustedbenz]

The thing actually has so many leaks that we're discovering every time we drive it a short distance that we're starting to think a significant amount of that volume could actually have possibly blown out instead of burned out. There was so much smoke it's obviously burning SOME -- but we're now tracing a leak or two including the turbo drain return tube that we think are at least confounding our tests, all other problems aside. I'll update the thread after I get another weekend at home to play with it, and confirm or disprove a few more things. Thanks again.

[vstech]

yeah, you can rule out the vacuum pump as a candidate, as it vents internally on the SD's it could easily be the catch can in the air cleaner, so be sure and follow the instructions I laid out in the other thread about the catch can to cut down on the oil in the air filter.
http://www.peachparts.com/shopforum/showthread.php?p=2586529#post2586529

[pgringo]

to check the turbo, make sure the engine is off, then remove the tube going from the air cleaner to the turbo inlet. then wiggle the turbo prop. there will be a lot of wiggle, about 1/4 inch from top to bottom, if the turbo is worn badly.

also, typically when the turbo is failing, you will get smoke in heavy acceleration, and another puff when you let off the pedal from hard acceleration.

[rscurtis]

Remove the breather hose and direct it into a one gallon container and drive the car. If you've collected a lot of oil, you have a BB problem. If not, there is some other problem.

As Brian mentioned, bad valve guides could cause this, not so much by oil going down the valve guides, but by pressure escaping into the VC area, causing excessive blow-by. When the engine is under load, both the intake and exhaust are pressurized.

I would think the easiest way to check for the turbo leaking would be to idle the engine for a short time and then disconnect the engine pipe and see if there is an oil residue in the exhaust.

If the rings were your sole problem, you would have considerable difficulty in even getting this car started.

[bustedbenz]

Originally Posted by rscurtis

Remove the breather hose and direct it into a one gallon container and drive the car. If you've collected a lot of oil, you have a BB problem. If not, there is some other problem.

As Brian mentioned, bad valve guides could cause this, not so much by oil going down the valve guides, but by pressure escaping into the VC area, causing excessive blow-by. When the engine is under load, both the intake and exhaust are pressurized.

I would think the easiest way to check for the turbo leaking would be to idle the engine for a short time and then disconnect the engine pipe and see if there is an oil residue in the exhaust.

If the rings were your sole problem, you would have considerable difficulty in even getting this car started.

Thanks to everybody who's posted. I'll post the results next time I'm with the car; I've got the 240 up here at the moment.

The car starts almost INSTANTLY when I crank it; it just about starts before I can let go of the key.

[odie]

Originally Posted by kerry

There is at least one other way oil can get into the combustion chamber--thru the PCV hose. Not saying that this is what happened, just that it is possible. I had an Austin Healey Sprite that was consuming gallons of oil that way.
My bet would be on the turbo.

how does the PVC hose suck oil? I thought it just sucked crankcase vapors. There is some oily smoke it's sucking but unless the PVC valve is in direct contact with a pool of oil I don't see how it would suck 3 quarts in just 100 miles.

I need to get back to my oil burner too...I had a sudden oil burn that went from zero to two quarts-per-miles in the span of about 10-15 miles. I pulled in for fuel and noticed a pretty bad smoking tail pipe. Left out and got the low oil light in about 2 miles. topped off and got 5-10 miles before low oil light again. topped off and not even a mile and low oil again.

my guess/hope is a blown turbo and not internal engine failure.

[bustedbenz]

Three updates on the car. Haven't seen it in person but talked to my dad on the phone tonight.

1) The entire underside of the car is soaked with oil, and we know for a fact that when we bought the car, it wasn't like that (rear axle boot replacement job soon after the purchase in August), which implies a recent failure or a new leak that's contributing greatly to the problem. So far we've found a serious leak at the oil pan end of the turbo return line and have got parts on the table waiting to go in to seal that leak up. It's not ALL of the problem but it's part of it.

2) He found a "line going from the turbo to the wastegate" -- that's how I heard the description if I didn't get a scrambled message from that phone call-- that was completely broken in two. Makes us suspect that the car's been running on full unregulated boost unless an auxilary over-boost protection circuit somewhere (something to do with the alda maybe, I've never quite understood that) -- with no signal reaching the wastegate to tell it when to open.

This car DOES have a noticeable turbo spooling noise under acceleration, more than the SDL. He pulled the air tube today and the turbo spins easily and does not wobble or spin out-of-round any. So no wear there. Yet another piece of evidence that the turbo seals aren't likely the source of our problem.

3) The check valve at the foot of the oil separator return seems to not be sealing. Oil flows freely down the tube into the sump -- well not "freely" but it does trickle... however, he put a mityvac on the thing and it wouldn't ever seal. Can suck oil up the tube through the absent-or-damaged check valve.

So... current theory is that in addition to leaking part of the oil out onto the ground, the chassis, everywhere... either excess boost, or normal ring blow-by, or a combination -- MIGHT have pressurized the crankcase enough to blow oil UP through a failed check valve, backwards through the separator, and through the air intake.

So we're addressing all of the above -- whether it's a good theory as to the consumption of oil or not, it needs to be taken care of anyway -- and then will test drive again and see if we've made any headway.

[kerry]

Originally Posted by odie

how does the PVC hose suck oil? I thought it just sucked crankcase vapors. There is some oily smoke it's sucking but unless the PVC valve is in direct contact with a pool of oil I don't see how it would suck 3 quarts in just 100 miles.
.

Not sure how exactly it happened on the Sprite since I was a mechanical neophyte at the time. But it was easily burning that much oil. The PCV valve on the Sprite did not come out of the valve cover but somewhere on the side of the block--perhaps from the covers over the pushrods. There was a defective check valve or something.
On a Benz, it would require a highly pressurized crankcase to have a similar effect.

[warmblood58]

Originally Posted by kerry

Not sure how exactly it happened on the Sprite since I was a mechanical neophyte at the time. But it was easily burning that much oil. The PCV valve on the Sprite did not come out of the valve cover but somewhere on the side of the block--perhaps from the covers over the pushrods. There was a defective check valve or something.
On a Benz, it would require a highly pressurized crankcase to have a similar effect.

Yep, I had a bad "gulp valve" on a MG Midget with 1275 engine -burned oil like a mother with an amazing smoke screen -