My experience with 240D and 300D vehicles is that they consume more oil as they age and yet they do not emit any blue smoke. I have read many threads and the experts say it is due to valve guide clearances having increased with wear.

I do not accept this as the full explanation. If this amount of oil is being ingested and burned then you will see it in the tailpipe. I have two solutions that need to be tested across a large group and the results need to be reported here. I would love it if the Engineers from Mercedes benz could also comment. I love my cars but I need to get their oil consumption down and with all of your great help out there we will succeed. If the Forum Administrator has a better way to coordinate results it would be well worthwhile.

Fix #1 Posted on the Blowby thread by Member F18 (Thank you F18):

Here is a trick that may reduce some of the oil in the blow-by off the valve cover vent. Sometimes the oil return galleys from under the valve cover on older engines get clogged up like arteries to and from your heart. This prevents the oil from returning back down to the oil sump fast enough and the valve cover gets flooded out. The extra oil gets splashed up into the oil separator in the cover and goes out with the Blow-By.

An old gear head told me to use a guitar string (low E with the Brass wire wrapped around it) like a long pipe cleaner and hone out the crud/tartar from the return oil galleys. You can run the guitar string all the way through to the sump in some holes. Then he said to run the engine to flush all the crud you knock lose to the pan and then change the oil. It works great if that’s your problem....and can reduce smoky exhaust and oil consumption.



Fix #2 Retrieved from old MB documents and supposedly an "Official MB Fix".....But I have not seen any "oil baffle plate" inside my Valve Covers so can someone help me here by explaining what they are talking about. Some pictures would be more than welcome. Here it is:

This fix is usually done when the valves get adjusted. Pull the valve cover off and look at the front edge of the oil baffle plate where it meets the inside of the valve cover close to the oil cap and breather. If it has been fixed, you'll see a gray epoxy covered area. If it needs fixing, you'll see about an eighth inch gap. Clean the area with brake-clean and apply epoxy. Don't use RTV. Don't use J-B Weld (it takes too long to dry and will ooze through the gap. The official stuff was Lock-Tight /NAPA 5-minute epoxy. It does an excellent job and is oil resistant.

Also make sure that you have the revised flat one piece hose that connects the valve cover vent to the air cleaner and not the
3 piece original one. It is inexpensive.

I can recall reading that burning oil does not become visible in the exhaust until it reaches something like a quart every 50 miles.
One drawback of our diesels is that we can't check for worn valve guides by backing off the accelerator on a long downhill and opening it up at the bottom looking for blue smoke like you can with a gasser.
Would it work to throttle the intake artificially somehow on a long downhill with a 616 or 617 and then see if it burns blue?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Long before worn valve guides cause excessive oil burning the oil stem SEALS will need replacing... that is a pretty straight forward job... my suggestion is that when you have it opened up to do that replace the valve rotators and the springs at the same time.....

+1.

That still doesn't narrow it down between valve stem seals or guides. The only real way to tell if your guides are bad is to remove your valve springs, push the valve in a little and then wiggle the valve stem. Trust me on this. I just narrowed down a 1 qt. per 500 miles oil consumption problem on my 911. Everyone told me it was the intake guides - turned out it was just valve stem seals. I saved myself about $5,000 on that one.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Well, I guess the question is where would the oil come from (to burn) if you have good valve stem guide seals ? If they don't allow the oil to get burned then why do you care about the technical clearance of the valve stems to the guides ?
Since both activities are accomplished with exactly the same labor down to that point... I say put it back together with the new valve stem seals and try it out... you have pointed out the financial reason to try exactly that before worrying about the stem to guide clearance...seals are really cheap...it is the labor getting there that is the pain...

Thank you for inputs so far.

I did replace the seals in my 300D to no effect.

That is why I am now claiming that one has to try the fixes #1 and #2 in my thread.

Will anybody comment on those fixes.....

Are you saying that as long as your valve stem seals are good, it doesn't matter if your guides are bad because the seals will prevent the oil from flowing into the combustion chamber? I really don't know the answer to that one. I would think that if your guides are bad enough, the valve stem would wiggle enough to keep the seals from sealing properly. With good guides there's only the slightest detectable movement. With worn guides you could have several millimeters of movement on the valve stem.

I do agree that the first step should be to replace the seals if you suspect one or the other if your main concern is to stop oil consumption - its fairly easy and cheap. However, if your guides are bad you do risk the valve eventually breaking off into the combustion chamber due to inadequate cooling from (a) the valve not mating properly against the valve seat and (2) lack of transfer of heat from the valve stem, to the guide, to the cylinder head due to the worn guide.

As far as labor goes, I guess it depends on the engine. On the 911 you have to remove the cylinder heads to extract the guides which is about an 80% engine teardown. To replace the seals, you just remove the rocker arms.

So what does all of this mean for the original poster? I have no idea but it has made for an interesting discussion. Besides, I think bad valve guides are fairly rare on these engines. Its probably just the seals - if even them.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

Since we're really doing some academic thinking here let's also consider the scenario of excessive backpressure feeding oil through the intake via the engine venting system. Do these cars have vent lines off the crank? I've never really thought about it before or looked. If you had a clogged cat or muffler or something causing a lot of backpressure, it would send oil from the main vent line from the crank back into your intake.

I actually removed the main vent line on my other car and vented it into a milk jug in my engine compartment and drove around a while to see if it collected any oil when chasing down a bad oil consumption problem.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)

For the OP....how much oil you using?

One comment...if the guides are loose I would think the new seals won't last very long and if they are really loose they may not seal well at all.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Some interesting statistics:
http://www.ms-motor-service.com/download/prospekte/KS_Oelverbrauch_en_web.pdf
...page 8...
in 24% of the registered cases of increased oil consumption the inline IP is to blame hmmm....

I very strongly encourage all members to look through the excellent reference proferred by Vox Incognita. Here it is again:

http://www.ms-motor-service.com/down...uch_en_web.pdf

One clearly sees that the problem is multi-faceted and the old retort that it is valve guides is a gross over-simplification. I did not say it is a non-contributor but what are the other contributors and how do we quantify their contributions.

What we now need to focus on is what are the heavy hitters on these MB Diesel engines for oil loss. I do not believe that valve stem seals are a solution in the presence of advanced guide wear. Consider a valve stem as a laterally oscillating lever and as such it is opening and distorting the relatively soft seal and thus compromising its effectiveness. Depending on resonances it is believeable that with some instances (the gentleman with the 911 above, for example) will get relief but not forever. He probably may see a return of the consumption over time but he is still better off financially to attend to a seal replacement every few years rather than an engine teardown. My experience has been that seals did not do it even in the short term on a 617 so I am now trying to address other methods.

Please go to the opening thread posting and talk of fixes #1 and #2 if you can. However all areas of this topic are most welcome and I applaud the excellent contributions so far. You guys are one great group. Think of this thread as a Think Tank and be as practical or as academic as you wish.

Scott:

This is a good method to measure the contribution to the oil consumption from the crankcase vent. Do you remember the results you got??

You should make a fairly tight seal, but not airtight, into the container to ensure the oil vapors condense out. To further ensure this I would place an inch of oil as primer on the bottom and run the tube into this oil to encourage full condensate recovery. I would also keep the collection container in the airstream to keep it cool thus further aiding condensation.

Let me know what you think......

My bet is on worn rings. If the lubrication rings are busted or if the clearance between the rings and the cylinder wall is to big, oil will find a way of passing through the compression rings. When oil gets there, it will in minimal quantities and therefore it will be burnt with the diesel/air mixture. Since the oil will be extremely hot and in small quantities, there will be no blue smoke. Maybe some increase in black smoke. Please note that an engine with fairly good compression might be burning oil through the rings, since worn lubrication rings will not affect compression in the cylinder...

Another reason might be worn compression rings. Since part of the combustion pressure will be discharged in the sump and the galleries, the added volume of air/smoke will find a way of going up to the valve cover, carrying oil particles. Due to the increased volume, the oil separator in the valve cover will not have the capacity of condensing all the oil and in will be ingested by the engine through the intake manifold.

Just my 2 cents...

__________________
1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.

Well stated points.

This is another way of saying that the crankcase pressure (and therefore also the valve cover pressure) increases and will make a contribution to blowby as well as pushing oil out through loose seals and gaskets.

I drilled holes in the milk jug to vent it as it does pressurize from the main vent normally. However, I had almost 0 oil coming through the main vent line. The problem did turn out to be the valve stem seals. My intake valve guides were all tight. So, in my case I got very lucky and solved the problem.

I am very interested to read more on this thread. My 240 consumes about 1 quart per 1,000 miles and I'd like to slow that down. I had contemplated replacing the valve stem seals because its cheap and easy just to see what kind of result, if any, I would get. I just haven't gotten around to doing it though.

Scott

__________________
Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)