My 1980 300SD developed a major oil leak while on a trip yesterday. The leak forced me to turn the car around and head for home. During about 300 miles I had to add a GALLON of oil. Prior to the trip the car had absolutely no fluid leaks of any kind and required only a small amount of oil be added every couple of weeks. This was our first out of town trip in the car.

I discovered the oil useage and leak when stoping for fuel. The entire back end of the car was covered with oil spots and the oil dipstick barely registered any oil. I added two quarts of oil which brought it back up to close to the full mark. Another thing I noticed was that the oil pressure gage needle would vibrate and make a noise when the engine was at idle. The gage needle still stays at max once you step on the "gas".

The only thing that was different on this outing was driving at interstate speed for a sustained period of time, around 70-75 miles per hour. This car is normally driven by my wife on short local trips around town.

Now for the specifics of the "leak". During the trip oil was dripping at the very back bottom of the engine. No evidence of any leaks on either side of the engine. The leak appears only to happen when the engine is running. Parked in the driveway I see only a couple of drops on the ground and that could be left over from the trip.

Could this be a leaking rear main seal? A MBZ machanic told me it is rare to see a leak at the rear main, especially with only 193,000 miles on the car. Or since the leak appeared while at sustained highway speed could it be coming from the turbo?

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• 2001 E320

Your best bet is to clean the engine in the driveway and run the car as short a distance as is necessary to cause it to start leaking again... perhaps it will do it in the driveway at 2000 rpm....shut it off then inspect carefully.... it is very hard when wind and oil pressure have spread the oil around....

Don't forget to take a close look at the oil pressure gauge "impulse" line from the oil filter area to behind the dash cluster.

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Jim

It is definately not the oil pressure gauge "impulse" line. The engine is dry on all areas that you can see from above. You can see where the oil drips to the ground by looking down on the passenger side of the engine back past the starter. Have not been able to get under the car yet for a better look.

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• 2001 E320

I believe there is a tube that drains the oil from the tubo back into the pan. I would check that and the oil feed line to the turbo. Since the leak is on the passenger side, I'd bet the problem is with the turbo oiling system somewhere. It seems hard to imagine that a rear main seal going bad would leak quite that much all at once.

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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

I had a similar problem that was the seal at the chain tensioner and front main seal..... same area and same oil leakage/usage.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k

Now I am really puzzled! Since getting back home, the leak has not gotten worse, in fact it appears to be significantly reduced. The driveway only shows a few oil drops, which could have just been from the oil already on the underside of the car. I was able to take a look under the car while on my ramps. There does appear to be a small amount of oil on the underside of the turbocharger. The largest amount of oil was near the rear of the engine at the transmission area. I could not pinpoint the source of the leak.

It still seems to me that the oil leak/useage is not significant at lower speeds around town. This problem appeared on our first trip at sustained highway speeds.

I know it is not recommended by many on this site, but I did add a bottle of stop leak to the oil for the return trip home. It is possible that this has also lessened the leak.

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• 2001 E320

They make 'stop leak' to go in the oil ? WOW... but I would change it as soon as you can...

If memory serves me right... at the rear of the engine there are at least to access holes to the oil passages... which are sealed by balls driven in the hole...these are access holes for cleaning the oil passages when cleaning the block... that might be a place at the location you are talking about to check out....and one which 'stop leak' might actually work on ....

Oil on the bottom of the turbo? Check the turbo oil feed line (on top, banjo bolt) and the oil return on the bottom. Both will leak more if hot, and the oil will drip off the bottom of the turbo or down the return line to the oil pan and blow back to the rear.

I had this exact thing happen to me on the Volvo -- didn't have the feed line tight after a turbo replacement. Got oil drops on the back of the car, oily mess everywhere, stopped when I tightened the feed line connection.

Needle bouncing at idle would indicate worn out crank bearings -- when the feed hole for the crankping (rod) bearing is covered, you have pressure, when it is not, all the pressure blows out.

It is possible for the rear main to be bad, and this means an engine overhaul -- no on will be willing to pull the crank and replace bad bearings just to put a new crank seal in, and it will go pretty fast if the bearings are bad, or the crank worn.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Since returning home the oil pressure needle has returned to normal. On the trip it would vibrate and make a noise when at idle. Now it is back to being rock solid at idle and will register at full pressure when underway. It would seem to me if the problem was a bad rear main and bad bearings the leak would always be present.

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• 2001 E320

The rear main will leak more at speed since you have more crankcase pressure from blowby, forcing the oil out -- this is another thing to check -- if the hose or oil separator is plugged, you can blow oil out everywhere!

Any oil at all on the turbo means either exess blowby dripping out the intake hose or leaking oil pipes.

What type of oil do you have in there? Could you be suffering from overly thin oil hot?

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I am using Chevron Delo 400 15W-40.

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• 2001 E320

A fellow Benz owner thought my problem might be bad valve seals. I am not convinced since the car starts right up with very little smoke. Also, why would I have an external leak if the problem was leaking valve seals? I am planning on cleaning off the oil from under the car this weekend and seeing if I can spot the source of the leak. It is certainly possible that at highway speed I am losing oil down the tailpipe as well as elsewhere on the lower part of the engine. With the wife driving the car the last couple of days on short trips around the area, it does not appear to be losing more oil. I only have a couple of drops on the driveway and when checking the dip stick it is almost to the full line. Is it possible that the turbo might be leaking internally and sending oil out the tailpipe? Any other ideas?

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• 2001 E320

Check the turbo for massive oil contamination -- pull the air intake hose off and see if the compressor is covered with oil, and there is oil dripping out the bottom of the housing. If so, the seals are shot. You will also have turbo troubles -- slow boost, or no boost, noise, or rough rotation (you can check that by spinning the intake wheel by hand ENGINE OFF, PLEASE). If it has rough or sticky spots in rotation, or moves back and forth, the seals and bearings are shot.

You usually have blue smoke under load with bad turbo seals since there is oil burning in the pipe behind the turbo.

You will also be pumping it down the intake when the turbo spins up -- more oil lost.

Check it out, I spent $750 on a cartridge (new guts) for the turbo on the Volvo, not too bad since I paid extra for shipping and overnight work!

A leaking vac pump will also suck quite a bit of oil out of the chain case and send it to the intake, too -- if there is oil in the air return line from the vac pump to the intake or air filter, fix the vac pump and oil consumption will drop dramatically.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Check your oil cooler lines for a pin hole. the oil cooler has a thermostat and oil is not always flowing in these lines. Had the same thing happen last winter on a long road trip up north. Lost a gallon of oil in Florida per 1/2 tank of fuel, nothing when in Ky and the outside temp was in the 30's.