oil consumption-anyone come up with anything? - PeachParts Mercedes-Benz Forum

SCOTTFISH · #1 11-13-2003, 04:54 PM

I have posted on this before, but am curious if anyone has come up with a solution to oil consumption of an inline 6 on a 89 300se. It uses a quart to quart 1/2 every 800-1000 miles. The car has 190k. I have had a valve job done, but piston rings were not checked/replaced. It still consumes. No dripping on garage floor. Using mobil 1 synthetic 0w40 made for MB & Porsche. Can travel 375 miles on a trip to Ky and have to put quart to quart 1/2 in that time. Drive the car for several miles short distance over a weekend period and drive home another 375 miles. The return trip home, most of the time does not use very much if any. Isn't this strange? Has anyone come up with anything on this as to what might be causing this?

dbenz1 · #2 11-13-2003, 06:31 PM

Whenever you are looking for an oil consumption problem, you start by changing the oil, logging the miles and checking the dipstick weekly. DO NOT add oil unless the level is AT OR BELOW the add mark. All engines use oil, some more than others and 90% of all engines are MORE than a quart low at 3k miles. That would mean that at around 2000-2500 miles, they were a quart low.

The MINIMUM level of usage is a quart every 750 miles, according to all the car makers. While that would be totally unacceptable for a new car, that is where we start planning the overhaul of an older engine.

Once you verify that you are using more than a quart every 1500 miles or less and you know you don't have an external oil leak, you would begin by pulling the spark plugs which will tell you which cylinder(s) is burning the oil. By performing a leak down test and a wet / dry test will then tell you if it is a piston ring or valve guide or seal problem. If your oil level is still above the add mark at 1500-2000 miles, everything is fine.

Piston ring problem --- No choice but to either wait it out or fix it by overhauling or replacing the engine. Cost will vary between $1500-4000 depending on the engine size.

Valve guides or seals --- IF you have a puff of blue or grey smoke from the tailpipe in the morning, IF you don't have any other smoke throughout the day, IF you have a very minor oil usage problem, IF you have between 60k to 100k on the old clock (speedo), all of that points to bad valve guides or seals. My advice is never fix this very expensive repair UNTIL you begin to use a lot of oil AND oil foul your spark plugs. Often you will have this "puff of blue or grey smoke first thing in the morning and never again during the day" for years before you foul your first spark plug.

You see, no one can be sure if your oil consumption problems are because of bad valve guides or seals. The seals typically cost $200-500 depending on the engine but to pull the heads and rebuild them will cost $850-1500. So what happens if they think it's bad seals and do all the work to replace them, and that doesn't fix your oil consumption problem? All of that money was wasted and you still have the same problem.

psfred · #3 11-13-2003, 07:15 PM

MB engines are pretty well known for using oil if overfilled, and synthetic oils are good about staying up in the engine instead of draining back into the pan, with the result that if you are in the habit of checking the oil while filling up, and add to keep the oil at the top mark, you may be "overfeeding" the engine, and it will cheerfully burn off the excess.

This has been verified by my mechanic friend, who actually bought a customer's car once that had "an oil consumption problem" -- problem vansished when he didn't add oil until the bottom mark -- oil level dropped to halfway between the marks and then stayted there for 3000 miles.

However, if you do have real oil consumption, you may have a ring problem. Dirty rings will stick and cause excessive oil consumption when run around town, but after acouple hours on the highway, unstick for a while and oil consumption drops to nothing. The 220D does this -- four quarts a tank, until you get it on the highway for about four hours -- no oil usage to speak of then until it gets cold again.

What I would do would be to check the oil only first thing in the morning, engine cold. Monitor lever daily, and only add a single quart if the level reaches the bottom mark on the dipstick. Your problem may go away!

If not, it's time for a leakdown test and plug examination.

Peter

haasman · #4 11-13-2003, 07:21 PM

I think fastbenz is offering very good advice. There have been several posts on this site regarding whether or not there is an oil consumption problem or not.

For me, I went through the same thing until I realized that 1) my driveway, where I will typically measure, has a slight incline from the garage door to the street 2) that the inline sixes seem to use oil somewhat quickly from about the full mark down to about the mid mark. I have read other people commenting on this as well.

I would never use a 0w-40. It is simply too light in my opinion but others reprot no problems.

We live in a fairly temperture climate where it rarely gets to freezing, lows mid to upper 30's at night (F) and during the commonly 65-70F during the winter.

Summer can get quite warm, above 100 is not uncommon multiple times during the summer. I have been using 10W-40 winter and 15W-50 summer. What I have noticed is both consumption and the engines seem to really like the 15W-50 oils.

The old 190e (87 with 220k miles) acted very differently when I first put in the 15W-50. Smoother and quieter right away.

Haasman

SCOTTFISH · #5 11-13-2003, 09:00 PM

When I had the valve job done and the problem got worse, I took it back and the MB mechanic totally reworked everything again. He did do a leak down test and it seemed to be ok. The heads were sent back to the machine shop and reworked. Then all new valve guides and seals were added along with new head gasket. The problem got better, but only back to where it was before the first valve job. Somewhere around 800 miles, the oil light will start coming on and remaining lit most of the time. After letting the car sit in the garage(level) for a minimum of 2-3 hours, I will check the oil level and it will be at the minimum mark. Only then will I add oil and it is usually a full quart. I find it hard to accept that it is ok for a car several years old to use a quart of oil every 750 miles, at least not a car that is driven daily and has had a valve job done. I have always used 10w30 oil in all my previous cars(not mb), but my local MB dealer recommended using Mobil 1 synthetic 0w40. Only on that advice did I switch to that oil. The "0" is supposed to be much better on cold starts but will give you the viscosity of 40 when running. Should the rings been replaced when the valve job was done or is that a totally more indepth process? Thanks to everyone for the discussion and information you all are sharing.

pesuazo · #6 11-13-2003, 09:12 PM

The rings are never touched during a head job, that is a much more involved process.
If they did a leakdown and a compression test, and the numbers came up normal, this is a mistery.
I will suggest to change your oil to a heavier weight 15W-50 or 20W-50 and see what the results are.
I have been running 20W-50 for years, and it consumes about a quart every 1500-2000 miles. The compression is really good, and the sparkplugs are dry. I have never seen a puff of blue or gray smoke coming out of the exhaust.

SCOTTFISH · #7 11-13-2003, 09:34 PM

When I switched to 20w50 once before, it began spotting the garage floor. It seemed to still consume oil, but I didn't have the oil in it long enough to know whether or not it would slow down. I changed it back to 40 weight and the spotting stopped. My mb mechanic is puzzled by this.

psfred · #8 11-13-2003, 11:07 PM

You aren't burning the oil, it's leaking out under load. If 20W 50 causes oil spots, the ligher oil is running off the engine at speed, doesn't leak at idle, so the oil drips off before you stop. Higher viscosity oil is still dripping when you get in the garage. A drip every couple minutes is a quart in 1000 miles or so!

check in the air cleaner housing where the large blowby tube is -- is it dry?

How old is your oil filler cap? My TE was using far too much oil (a quart in 1000 miles or so) -- I've changed the valve cover gasket, was expecting to do the front cover, and discovered that the valve cover gasket was oily again. So was the area around the oil filler cap. Gasket on the cap was rock hard and premanently dented where it is supposed to seal, so on the highway, oil oozed out. Ran off the engine, left occasional drops on the drive. New oil filler cap, so far on oil useage.

Other things to check are for oil in the sound insulation tray underneath, and for a drop hanging at the bell housing (rear seal). I assume you don't have the front cover leak so very common on the M103 since you just had the head done. Make sure the PCV purge hose (the samll one between head and intake) isn't plugged.

Still, take a look at the plugs. Crusty residue on the center electrode at relatively low milage is and indication of burning oil, you will then have to find where it is getting into the engine.

Unless the valve guides have excessive clearance, it's not going down there. You also don't have the valve cover filling up with oil, either, it goes down the chain case.

I'd lood for a leak somewhere on the block that runs off into the sound insulation panel.

Peter

Mike Murrell · #9 11-14-2003, 12:17 AM

Scottfish:

Peter's last post says alot.

I more or less have the same vehicle as you; mine is a 1991.

I was using a qt. every 1000 and a new head gasket and valve stem seals cured that. I'll assume the people who did your valve job did indeed change guides, seals, OEM head gasket and also replaced the infamous U-Gasket up front. If all of that was done, you have a leak.

The 103 motors are "leakers".

SCOTTFISH · #10 11-19-2003, 10:01 AM

My wife stated last night that the car was running really bad. I went out and pulled the plugs and 4 of the 6 plugs looked to be fouled out by oil getting into the spark plugs to the point that the carbon build up was so thick, I am surprised the car would even run. If I am having this major build up with oil getting into the plugs, what do you think could be allowing this to happen?

gidpor · #11 11-19-2003, 10:35 AM

"Can travel 375 miles on a trip to Ky and have to put quart to quart 1/2 in that time. Drive the car for several miles short distance over a weekend period and drive home another 375 miles. The return trip home, most of the time does not use very much if any. Isn't this strange?"

My comment is in regard to your opening question as stated above.
During this recent trip were you driving the car harder on the way out ? I have found(and others here have reported the same) that when city driving the 103 consumes less oil than during Highway driving. Furthermore along those lines - The faster you go, the more oil you will burn.

Mike Murrell · #12 11-19-2003, 12:07 PM

Scott:

You mentioned valve job. I can't help but wonder about the quality of the work, especially what was done to the cyl. head and if it was done correctly. Sounds like somethings getting past seals/guides. Which one - who knows?

Unless your oil change regimen is terrible or the car was run low on oil or too hot, too often, I wouldn't suspect rings.

SCOTTFISH · #13 11-19-2003, 01:37 PM

Mike, I wonder if the rings just got majorly gummed up and are not allowed to clean the walls as their are supposed to. The records I got with the car show a history of pretty regular oil changes at 3k. I wonder if the machine shop that did the heads is as good as my mb mechanic wants to think. First vjob, began using 3 quarts in 800 miles. Redone and everything tightened up and it went back to where it was b4 the first vjob. This machine shop is a different shop from where the dealer uses. I have wondered about the shop myself. Oh, well, we will keep trying until maybe one day we figure this thing out.

300EE320 · #14 11-19-2003, 06:48 PM

Manufacturers of new cars have to balance the choice between bore wear and horsepower lost to friction, with oil consumption. It all comes down to low versus normal tension oil rings. The happy medium is the use of some oil, while keeping power maximized. When I think of it this way, I am happy to add oil on occasion knowing that I'm not loosing power to friction.

On your car, it may very well be that a gummed up ring land is not allowing one or more oil rings to do its job of sealing, or it may be that the oil rings have lost tension over the years.

If it were me, I wouldn't worry about it. But I would run cheaper oil if I was consuming it.

psfred · #15 11-19-2003, 07:03 PM

Scott:

If you have gunked up plugs, for sure you're burning it. However, there are several ways for oil to get to the plugs.

Bad valve guides are a possibility, especially if the shop that did the head isn't familiar with MB specs. They may have left bad guides in there, or reamed the new ones for clearance, which is wrong. Proper clearance on MB valve guides is basically zero -- if the oiled valve stem will go into the guide by hand, the clearance is fine. If you depress the valve (minus spring) to lift it off the seat and can move it sideways in the guide, the guide has too much clearance. Excess clearance and the oil pours down the engine. It should smoke, though , on startup if this is the case. Also, you will have idle and mixure problems from the air going down the guides -- they can get so bad it's impossible to set the idle mixture properly, with rich running at high rpm. Check via the duty cylce diagnostic.

Another possibility is bad oil rings from being badly overheated -- this anneals the spring on the oil control rings, and the won't scrape the oil down like they are supposed to. Compression will be fine, no leakdown problems since the rest of the rings are OK.

Excess blowby is a given -- but this should give you an oily air filter housing. My TE has a completely dry air filter housing, no oil. So does the 280. However, if the orifice in the other breather tube (the small one between the head and the intake manifold) is too large, you may be sucking oil off the head. Would probably foul 2,3,4,and 5 more than 1& 6, with 3 and 4 the worst. I don't believe th large ventilation hose could get plugged to cause crankcase pressurization, but check that too.

Bad valve guide seals won't give you THAT much oil consumption, I don't think, but they are the cheapest fix.

Peter