OM617 Ran out of oil - PeachParts Mercedes-Benz Forum

cfh · #1 08-07-2015, 10:54 AM

This is embarrassing - I un-bolted the turbo oil feed to upgrade the air cleaner mount; put my new beefed-up bracket in and bolted everything up. It was late and I DID NOT start the car and check for leaks. Next day I take the car out and notice after about 5 minutes (last 1 minute of which was at highway speed) I hear a slight "tick tick" (no loss of power) and look at the gauges and see very low oil pressure. Shut it down, pulled over, got it towed back in. It's been sitting for a few days - haven't touched it but I have a feeling the engine is toast. I have a good spare.

Should I proceed directly to swapping in the spare or is there maybe some hope for the abused motor?

Thanks.

leathermang · #2 08-07-2015, 11:02 AM

if any oil pressure still showed...
put oil and new filter back into it....
and try it out...
the oil pumps are very strong...
the description of your event leaves room for possible ' miracle '.....
your reaction to what you saw was correct... stop and tow home...
this might be a good time for the discussion on AUDIBLE low oil pressure warnings equipment to be discussed....
but don't do that again....

t walgamuth · #3 08-07-2015, 11:33 AM

Yep. Change oil and try it out. Maybe you'll get by with it.

Good luck!

mach4 · #4 08-07-2015, 11:52 AM

You've got nothing to lose....fire it up.

If it runs OK, then start down the path of seeing what the damage might be - check the compression, inspect the cam and so forth. Listen for strange noises and watch the oil pressure. Don't venture too far from home until you've got some experience with it.

As already stated, you might get lucky.

cfh · #5 08-07-2015, 12:46 PM

Wow - quick replies from some of the heavy hitters on this forum - thanks guys!

For anyone else who reads this thread, please take note of the obvious lesson - never, ever, after working on a car, just button it up and say good to go, without first starting it up and doing a visual check for leaks or problems.

Upon returning home I felt so stupid when I saw the little trail of oil leading away from my house - the problem (whatever it turns out to be) would have been very easy to spot if I'd just taken that extra minute to check it out.

Well I learn from my mistakes, maybe someone will, too. -- Ch

mach4 · #6 08-07-2015, 01:23 PM

So the good news is that you chose to dump your oil on the road through the turbo feed line, which has a restrictor of something like .03 - .06" to keep from over feeding the turbo bearings, as opposed to something like the oil cooler lines which are about 1/2 inch. This means the oil pressure likely had a chance to decline gradually rather than abruptly giving you time to notice and the time things were starved potentially pretty short.

We can always hope....

mannys9130 · #7 08-07-2015, 01:43 PM

Don't get your hopes up, but try to resurrect it. Refill with oil and try to start. If it doesn't want to turn over, fill the engine all the way (as in completely up into the valve cover) with oil and let it sit for a day. Drain the oil out to the proper fill level, pull the glow plugs out, and put a ratchet on the crank. Try to turn it over (clockwise only) and if it does, turn the engine several times to get all the oil out of the cylinders. Once it's rotating freely, try to start it again. If it seems to have been saved, run it carefully. If your hot oil pressure is noticeably lower than it was before, you have done damage to the main and rod bearings.

I'd get that spare engine prepped for surgery just to be safe.

BillGrissom · #8 08-07-2015, 03:06 PM

One small data point. A guy did this experiment for me in 1991, delivering my 1982 Dodge Aries cross-country via a "Drive-away Service". The contract said they would check the oil level "every 100 miles". The German tourist who delivered it said he didn't know much about cars. I found the oil lamp lit and ~1 qt left in the pan. Not his fault, the service had first done an oil change for me without asking (charged me $$$, plus bogus "muffler repair", thanks) while holding my car hostage 2200 miles away, and the fool didn't tighten the oil drain plug.

Not exactly your engine, but a 4 cyl SOHC so fairly similar in the oiling department. The only apparent damage appeared to be a worn camshaft (tapping noise). I had the cam re-ground and drove the car fine for many more years. I heard stories of Vega engines (early U.S. OHC engine) failing the camshaft regularly, until people learned to enlarge the oil feed.

Not much to hang on, but suspect the first damage would be in the camshaft, so if your valve clearances haven't changed appreciably (and thus no noises), the engine is probably fine. BTW, journal bearings don't actually need pressurized oil, just a supply of oil. Indeed, the (half) bearings on train wheels were oiled by the bottom half of the axle sitting in a reservoir, drawing oil up into the top half. At each station, a worker would walk the wheels, check the oil level in each, with a clang as he dropped the top of each, which you see in old movies. The pressure which floats the axle is developed by the rotation, and took a while for scientists to understand that.

mannys9130 · #9 08-07-2015, 03:31 PM

Quote:

Originally Posted by BillGrissom

BTW, journal bearings don't actually need pressurized oil, just a supply of oil.

That is very incorrect. They need pressurized oil to suspend the journal exactly in the middle of the bearing, minimizing metal on metal contact. They require both a certain pressure and a certain flow rate to do this.

Where in the world did you get this information and why would you pass it as truth?

97 SL320 · #10 08-07-2015, 04:13 PM

Before you go any farther, did you pull the dipstick and see if there is any showing? Next step is to drain the pan and see what was in there.

If there was at least 2 QT in the pan, I'd be more concerned about the turbo.

leathermang · #11 08-07-2015, 06:11 PM

Quote:

Originally Posted by mannys9130

......Where in the world did you get this information and why would you pass it as truth?

Good luck getting a straight answer on that... have you seen his posts on Duracool and HC's ?

Just to elaborate on why Bill's post was SO Wrong.... the piston pin oil is supplied off a hole in the crankshaft under the big rod bearing....

Frank Reiner · #12 08-07-2015, 08:17 PM

Quote:

Originally Posted by BillGrissom

One small data point. A guy did this experiment for me in 1991, delivering my 1982 Dodge Aries cross-country via a "Drive-away Service". The contract said they would check the oil level "every 100 miles". The German tourist who delivered it said he didn't know much about cars. I found the oil lamp lit and ~1 qt left in the pan. Not his fault, the service had first done an oil change for me without asking (charged me $$$, plus bogus "muffler repair", thanks) while holding my car hostage 2200 miles away, and the fool didn't tighten the oil drain plug.

Not exactly your engine, but a 4 cyl SOHC so fairly similar in the oiling department. The only apparent damage appeared to be a worn camshaft (tapping noise). I had the cam re-ground and drove the car fine for many more years. I heard stories of Vega engines (early U.S. OHC engine) failing the camshaft regularly, until people learned to enlarge the oil feed.

Not much to hang on, but suspect the first damage would be in the camshaft, so if your valve clearances haven't changed appreciably (and thus no noises), the engine is probably fine. BTW, journal bearings don't actually need pressurized oil, just a supply of oil. Indeed, the (half) bearings on train wheels were oiled by the bottom half of the axle sitting in a reservoir, drawing oil up into the top half. At each station, a worker would walk the wheels, check the oil level in each, with a clang as he dropped the top of each, which you see in old movies. The pressure which floats the axle is developed by the rotation, and took a while for scientists to understand that.

It may be instructive for those who have an interest in the lubrication of plain journal bearings to consider the following from Wikipedia:

Fluid lubrication

A schematic of a journal bearing under a hydrodynamic lubrication state showing how the journal centerline shifts from the bearing centerline.
Note that the center of the journal is not in the center of the bearing shell, as was stated above. [FR]

See also: Fluid bearing
Fluid lubrication results in a full-film or a boundary condition lubrication mode. A properly designed bearing system reduces friction by eliminating surface-to-surface contact between the journal and bearing through fluid dynamic effects.
Fluid bearings can be hydrostatically or hydrodynamically lubricated. Hydrostatically lubricated bearings are lubricated by an external pump that maintains a static amount of pressure. In a hydrodynamic bearing the pressure in the oil film is maintained by the rotation of the journal. Hydrostatic bearings enter a hydrodynamic state when the journal is rotating.[11] Hydrostatic bearings usually use oil, while hydrodynamic bearings can use oil or grease, however bearings can be designed to use whatever fluid is available, and several pump designs use the pumped fluid as a lubricant.[citation needed]
Hydrodynamic bearings require greater care in design and operation than hydrostatic bearings. They are also more prone to initial wear because lubrication does not occur until there is rotation of the shaft. At low rotational speeds the lubrication may not attain complete separation between shaft and bushing. As a result, hydrodynamic bearings may be aided by secondary bearings that support the shaft during start and stop periods, protecting the fine tolerance machined surfaces of the journal bearing. On the other hand, hydrodynamic bearings are simpler to install and are less expensive.[citation needed]
In the hydrodynamic state a lubrication "wedge" forms, which lifts the journal. The journal also slightly shifts horizontally in the direction of rotation. The location of the journal is measured by the attitude angle, which is the angle formed between the vertical and a line that crosses through the center of the journal and the center of the bearing, and the eccentricity ratio, which is the ratio of the distance of the centre of the journal from the centre of the bearing, to the overall radial clearance. The attitude angle and eccentricity ratio are dependent on the direction and speed of rotation and the load. In hydrostatic bearings the oil pressure also affects the eccentricity ratio. In electromagnetic equipment like motors, electromagnetic forces can counteract gravity loads, causing the journal to take up unusual positions.[11]
One disadvantage specific to fluid-lubricated, hydrodynamic journal bearings in high-speed machinery is oil whirl—a self-excited vibration of the journal. Oil whirl occurs when the lubrication wedge becomes unstable: small disturbances of the journal result in reaction forces from the oil film, which cause further movement, causing both the oil film and the journal to "whirl" around the bearing shell. Typically the whirl frequency is around 42% of the journal turning speed. In extreme cases oil whirl leads to direct contact between the journal and the bearing, which quickly wears out the bearing. In some cases the frequency of the whirl coincides with and "locks on to" the critical speed of the machine shaft; this condition is known as "oil whip". Oil whip can be very destructive.[11][32]

A lemon bore

Oil whirl can be prevented by a stabilising force applied to the journal. A number of bearing designs seek to use bearing geometry to either provide an obstacle to the whirling fluid or to provide a stabilising load to minimize whirl. One such is called the lemon bore or elliptical bore. In this design, shims are installed between the two halves of the bearing housing and then the bore is machined to size. After the shims are removed, the bore resembles a lemon shape, which decreases the clearance in one direction of the bore and increases the pre-load in that direction. The disadvantage of this design is its lower load carrying capacity, as compared to typical journal bearings. It is also still susceptible to oil whirl at high speeds, however its cost is relatively low.[11]

A pressure dam

Another design is the pressure dam or dammed groove,[33] which has a shallow relief cut in the center of the bearing over the top half of the bearing. The groove abruptly stops in order to create a downward force to stabilize the journal. This design has a high load capacity and corrects most oil whirl situations. The disadvantage is that it only works in one direction. Offsetting the bearing halves does the same thing as the pressure dam. The only difference is the load capacity increases as the offset increases.[11]
A more radical design is the tilting-pad design, which uses multiple pads that are designed to move with changing loads. It is usually used in very large applications but also finds extensive application in modern turbomachinery because it almost completely eliminates oil whirl.

Indeed, the need for an external supply of pumped oil is simply to replace what leaks out.

leathermang · #13 08-07-2015, 09:03 PM

Quote:

Originally Posted by Frank Reiner

....

Indeed, the need for an external supply of pumped oil is simply to replace what leaks out.

On our engines we are talking about a design which uses some of the oil which lubes the rod to crank throw to send up the piston rod to keep the piston pins lubricated... so pressure is needed no matter how much or little ' leak ' might happen on the crank journal. The Wiki article was talking about a typical sealed machine bearing. So our pressure needs are amplified even farther than their example.

mannys9130 · #14 08-08-2015, 03:23 PM

A 3-8 hp lawn mower engine is the only engine I can think of that doesn't have pressure lubricated rod and main bearings. They're flathead engines with oil slingers and sloppy tolerances on everything. They last a few thousand hours and then are destined for the dump. The oil pressure suspended journals keep the bearings intact for a couple hundred thousand miles at 200 HP.

BillGrissom · #15 08-08-2015, 04:34 PM

Thanks to Frank for explaining.
Manny, I learned journal bearing lubrication in mechanical engineering courses (have an M.S.).
Leathermag is correct that the piston pin is different in that it is not a continuous spinning journal bearing. But, 2 miles of moderate driving probably did not damage it.
I appreciate all you guys reading my posts and hope everyone will do their own research, as Frank did.
I do tend to air on the side of "probably nothing to worry about", rather than those who knee-jerk respond, "best to rebuild the engine" or that new products mentioned have all these imagined problems (e.g. HC refrigerants, silicone brake fluid, waterless coolant that I use). Read, learn, think. It works for me and has helped keep all my cars working, and I have learned much on this site. Indeed, maintaining my 2 M-B would be an untenable proposition without the info here.