Like the title says, my OM617 on the 83 300D started leaking oil fairly significantly from the oil cap on the valve cover. Here is the background on it. It has not leaked at all before, then last weekend, I did an oil and oil filter change, using Shell Rotella T6 synthetic oil for the first time (used regular 15W40 dino oil in the past). A couple of days ago I noticed some oil drops under the car. I popped the hood and found oil around the filler cap on the valve cover. Today driving home I faintly smelled hot oil so I pulled over to check and found a significant amount of oil around the oil cap and on the valve cover. I cleaned it off and drove the remaining 15 miles home. Got home, and the valve cover around the oil cap was covered in oil again. The oil cap and seal look ok, but it is the original metal cap and seal. So, should a new cap and seal fix the issue, or could it be because I switched to synthetic oil?

Suggestions??

__________________
2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)

Probably a bit of each. Thinner oil and an old seal. Put it all back as it was and you'll probably be fine.

__________________
[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.

When my oil cap started to leak, I shimmed the rubber seal with a piece of plastic from a milk jug. No leaks since.

__________________
When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Your vent hose is not totally obstructed. Or the engine would quit. Make sure it is reasonably clear though.


Synthetic oils where modified to stop the characteristic of causing leaks where none existed before. Still it may have a small remaining component of that effect.

Synthetic oil has a tendency to leak more

Those days are gone forever. Time to forget this urban legend.

Not totally and it was factual as the formulas where changed to overcome the problem. It still retains a cleaning action. If you want to get more technical the base pressure may have increased with the new oil. Just enough to overcome an old gasket. Do the blowby test with the cap loose.


I have no interest in oil type threads. Logically there will be a different molecular size between the base components of each type. A typical example that we do not see anymore.


You have a car in the day using just plain water as the coolant. You change over to a 50/50 mix of antifreeze and water for the winter. The water pumps or water pumps in the case of the old ford flatheads started leaking. To me it was a molecular size difference that created the problem. The smaller molecule was passing the seal where the other could not. I have no doubt that this does not sound real to some. Yet it was on some cases.


When I pressure check refrigeration systems I do not use nitrogen. I use argon as my inert gas because the molecule is even smaller. Nitrogen is the industry standard. I just take it a little farther. Technically if I want to observe a test period. I can shorten it up if I wish to. Or to put it in another way. If it will hold nitrogen. It may not hold argon. Still I see no issue with using nitrogen.

Vent hose is clear, I actually disconnected it at the air cleaner end and ran the open end to a temporary catch can to check it during a 20 mile run and only had a quarter sized spot of oil in the can.

__________________
2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)

I don't know anything about urban legend. I've owned a BMW R75/7 for over 30 years. Never put full synthetic in it till about four years ago. It started leaking from the pushrod tubes where they are pressed into the heads. Switched back to dino oil, stopped leaking. Enough evidence for me.

I'd only put synthetic in an old engine if it had all new bearings and seals.

__________________
[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.

Just for funs, try using the fuel filler cap in lieu, I bet that stops the weeping dead .

There was recently a thread here that discussed why the original typ oil caps were beginning to leak, it included a cut away cap showing the inner seal that apparently dries out allowing oil to work past .

I had an old fuel filler cap and tried it, BINGO ! it doesn't sit with the raised part where I like it but not a drop of oil escapes now......

I've never had any luck with the replacement oil filler caps not leaking badly .

FWIW, the new upgraded oil & fuel cap GASKET is BLUE and works ever so much better than the old black ones .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Well, I got a new oil cap and that seems to have solved the issue for now. If it starts again, I will try the fuel filler cap trick and order a BLUE replacement gasket.

Thanks

__________________
2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)

I've run full synthetic for every fluid in every car I've owned for past ten years or so. I don't really think synthetic oil is prone to leaking, though it does clean out deposits around seals and I do see a lot of people who run 0 or 5 W synthetic who complain about leaks. I would think 0 or 5 W conventional oil would leak, too. I don't like running oil lower than 15 W.

I've used the blue replacement gaskets from Uncle Kent for the valve cover and fuel filler cap gaskets--mostly for the fuel filler cap because I run biodiesel. I wish someone would come out with a biodiesel-compatible fuel filler gasket so mine would stop melting.

__________________
Stop paying for animal enslavement, cruelty, and slaughter. Save your health and the planet. Go vegan! I did 18 years ago. https://challenge22.com/

DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles

There's no 'urban myth' to it ~

Those who claim there is simply don't have the experience with older higher mileage engines as one of the many benefits of fully synthetic oils is : in addition to being incredibly detergent (yes, you can actually drive the engine clean), they also creep into more areas that does dino based oils to they weep & seep more, not so much 'leak' as they show the weeps & seeps you already had, much faster......

I use almost always fully synthetic oils and they stay mostly inside my high mileage heavy usage engines, some of the older tech engines do show more wetness around the seals and gaskets, no question about it .

Many here should run the 5W ~ whatever oils but prolly not in Arizona or other hot Desert climes .

Oil threads are always firefights because closed minds are scared of learning new things .

One of my oldies is a 1969 Honda 90CC Motocycle, I switched it to fully synthetic oils decades ago and it now had over 40,000 miles on it and still runs well .

Yes, it has some dampness here and there in spite of being the pride of Honda but no, it doesn't use more than a table spoon of oil between hot changes .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I hate oil threads but ...

I too use synthetics in all my machinery. It is simply a superior lubricant. I do however pay attention to the recommended ooil weight specs. In my OM617 turbodiesel, I use 15w-40. No leaks to speak of. I did dry the engine up as best I could and after replacing the turbo drain tube o-rings the major leak source went away. The only leak now is a 50-cent sized overnight drip from the rear crank seal. I'm never going to fix it. The car uses/loses about a half quart between 6000 mile oil changes. I could probably go much longer.

I agree that those who attempt to use a lighter weight oil than recommended are asking for leaks.

My oil of choice is AMSOIL. I use it in everything from cars to weedwhackers and outboard motors. Great stuff.