Just developed an intermittent oil leak that has got me puzzled. It only happens every few weeks and it seems to come only at highway speeds. After I clean the motor and drive it around town it doesn't leak but if I get up to 70+, oil pours out the left side of the motor around the injector pump area. The problem is that I can't find the leak because once it starts, oil is everywhere and when I stop and pop the hood, the leak stops.

Any suggestions?

Mav

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'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

First things that come to mind are oil cooler return hoses and fittings and power steering hoses and fittings, are you 100% sure its motor oill? Could be power steering fluid...

Definitely motor oil. In fact in one occurrence, I went through about 9 quarts of oil in 200 miles, shut her down for a few hours, drove back a few more hours and it didn’t leak a drop!

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'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Mav:

Two thoughts:

The IP is engine oil lubricated on the bottom side -- I don't know if there are external lines or not, but if you have a bad gasket, it could leak. I know the bottom cover leaks, and it is necessary to remove the IP to fix it -- requires several special tools to retain correct timer to pump alignment and to avoid breaking the timer. Also a hube pain in the ass. Better than blowing all the oil on the ground!

Second, make sure your blowby hose isn't clogged either in the hose to the turbo or inside the valve cover in the oil separator -- if it is, you will overpressure the engine hot at speed, and out comes the oil, probably from the injection pump flange or bottom plate! My old 220D has too much blowby, and on the highway blows oil out the upper oil pump busshing seal like mad!

Since you should have a slow leak along with the big one, clean the engine and spray it with foot powder -- you will be able to see leaks better as black streaks in the white powder. Otherwise, if you are using good oil, it will run off and not leave much mark.

I cannot personally think of anything else, but I'm sure at least one other person will!

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!

Hey Peter,

I think you’re right about too much crankcase pressure and I just realized it today after staring at the motor for a few more hours. A while back I broke the breather hose and elbow that goes from the valve cover to the intake hose right after the cleaner. The old hose was very thin walled and cracked so I replaced it with some clear tubing that fit well in the new valve cover elbow fitting but loosely in the other end. This morning I pushed it in further for a better seal. With that problem fixed hopefully the vacuum will ease up some of the pressure in the block. Further, the injection pump flange or bottom plate is right about where the oil seems to be coming from.

By the way, what is the IP?

Thanks much…

Mav

__________________
'91 350SDL 165K miles
Lovin' her until she blows...
'01 Dodge Ram Cummins 4X4 DWR
Stump pullin' beast...

Mav:

Injection pump. I'm lazy, easier to type IP.

I broke the blowby "hose" --really a plastic pipe, I think -- on my 300D when I replaced the thermostat -- spliced it with heater hose since the gromet in the valve cover is rock hard.

Do you have much oil in the hose? If so, I'd suspect a blowby problem, too.

If you can get the elbow out, check if for crud -- if not, get a new one and break the old one out, get a new grommet too. Even a good condition diesel will build up considerable crankcase pressure if the vent is plugged off!

Any idea of what driving conditions results in oil leakage?

Peter

__________________
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!

Maverick,

On my old 1975 240D the injection pump had a little red cap with "OEL" written on it. If you pulled it out, there was a little dipstick hanging there to measure the oil in the lower end of the injection pump. I am not sure if the 350SD has this feature or not, but along with the little red cap was a small tube that came up and then bent 180 degrees to point at the driveway. Well, once upon a time I was changing oil in a buddy's parent's driveway and I got done, saw this little red cap and thought I ought to check it out. So I pulled it and found the oil level above the bottom mark, but below the mid point of the span to full. So, I thought I should top it off. Well, I poured a little late '70s Mobil 1 of a near water viscosity in and checked again. Still looked a little low, so I poured some more in. After two quarts, I noticed oil building up on my sneaker as it ran down the driveway. And then I discovered that little vent/drain tube. I never got invited to work on cars at that buddy's house again.

Anyway, that car did not have any injection pump to engine oil connection. The stuff that was in there was clean as new oil. Even before I did what I did. But if the new ones do, and they have a little "U" shaped tube on the inside wall of the injection pump, you may be getting oil out of that tube. Can't go check a car since I no longer have a 350SD, but thought I would pass on the story. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)