(1983 300D) 70mph + steep hill = leaking oil and odd smell - PeachParts Mercedes-Benz Forum

Cinnamonandgravy · #1 02-25-2015, 01:17 AM

So I might've been a dummy. Story time.

1983 300D. some assorted issues, and slight oil/coolant leaks, but otherwise solid. Recently changed the oil, maybe 3 weeks ago (Rotella 15W-40 - what I always use).

So I recently switched jobs, and my training was at a location ~30 miles from my house. Quickest route was via toll roads, and the toll roads round these parts are pleasant, very hilly drives. So I took the 300D for its first time on the toll road.

There are a few long, steep climbs, and the 300D was very happy to soldier up them at ~70mph. During the climbs, the engine temp never went over 85, and fairly quickly went back down to ~50-70 after climbing the hills (my normal temps). RPMs were low 3k's.

After getting home, I noticed a few oil drops going up the driveway. Looked under the car, and while the car normally leaks a bit of oil and drips from the regular places, it was clear oil was thrown over the undercarriage, and the car was consequently dripping from many new places.

I lift the hood and notice some oil thrown over the fuel injector pump, over 1 glow plug (the one closest to the front of the car), the oil dipstick handle, and noticed the oil dipstick tube was covered in a fair amount of oil, as well.

I think to myself, 'oh crap, maybe 70mph wasnt the smartest. hope i didnt rupture something and push out half the oil or more'.

Pull out the oil dipstick, and I find the oil level is now at the bottom notch (thank god). Just 3 weeks ago it was at the top notch. But I also notice an odd smell. Not quite burnt oil (I think), but I couldnt place my finger on it. Thought maybe coolant had mixed in, but the coolant levels looks normal enough.

Removed the oil cap to add fresh oil, and noticed a slight smell again.

This was ~4 hours ago. The car has since stop leaking oil from the new places. Starts up fine and runs well.

Any thoughts? I'll be taking the car on the same trip tomorrow, just at a slower pace, ha. The smell and it pushing out oil is scary though.

rscurtis · #2 02-25-2015, 10:55 AM

Check your oil cooler hoses.

PackerEdgerton · #3 02-25-2015, 11:55 AM

Oil leaks don't cure themselves. I agree, check your oil cooler hoses, and figure out where the oil is coming from. Clean the engine off and let it run while you check the possible sources.

Good luck,

PE

barry12345 · #4 02-25-2015, 12:46 PM

If oil cooler line leaking. May or may not be more present when the oil temperature thermostat is open. Hotter oil is thinner perhaps may be another factor.

Also check your engine mount as it may allow rubbing of the hose by a belt if collapsed.

I am really old school but still find I do not check oil levels very often on our newer cars. Still I never make this error on older cars.

If one reduces this practice on them. At least once checking on every fill up. You should really install some form of low oil pressure alarm.

It is preventative maintenance to change out old oil cooler hoses. Especially if one has no ideal of how old they are. Neglecting this type of thing can cost you the engine. Over time they will eventually fail is almost a certainty. I would not highway drive this car until the source of the leak I found. If a hose it could totally let go and by the time you know it. Your next post could be pretty catastrophic.

vstech · #5 02-25-2015, 01:18 PM

if the cooler hoses are ok, pull the dipstick and replace the o-ring. it'll shoot oil everywhere if crank pressure builds from a long hilly drive.
also, pull the air cleaner, and make sure the catch can is not broken, and make sure the tube from the valve cover is not damaged.

charmalu · #6 02-25-2015, 01:57 PM

I agree with the above, check the Oil Cooler lines.

You mention that the temp never got over 80, and then went back down to 50 - 70.
That is too cool, 80 is where it should run normally, and climb a little above that on a good climb.

Replace your Thermostat, and that should fix it.

As berry mentioned, a collapsed engine mount will let a belt (power steering) rub the cooler hose and cut through it.

Charlie

Cinnamonandgravy · #7 02-25-2015, 10:44 PM

thanks for the replies, everyone.

oil cooler lines are fine. if one of those went, i wouldnt just have oil on a single glow plug and some on the fuel injector pump

i agree with vstech - the various rubber o-rings on this car were very neglected from the previous owner (the 2 from the oil filter housing were unbelievably hard) so the oil dipstick o-ring is very suspect. given most of the visible oil was spilled around there, and the dipstick tube is fairly filthy, this is a good place for me to start.

Cinnamonandgravy · #8 02-26-2015, 12:24 AM

so i changed the oil dipstick o-ring (thank you, metric o-ring value pack) and while this o-ring wasnt nearly as bad as the oil filter housing ones (those were rock hard and came out in pieces after way too much effort), this o-ring was certainly past its prime. flat edges, a bit small, and not much elasticity.

with the old o-ring, the dipstick would just easily slide out when pulled. now it offers resistance, and almost has a *thunk* when putting the dipstick back in. actually feels like its making a seal.

noticed the breather tube atop the valve cover was a bit messy, too. the oil cap gasket has needed replacing for a while now, and if im going with vstech's theory of crank pressure, this makes sense. the top of the valve cover was a little extra messy, and there was a trail from the oil cap to the breather tube. the breather tube itself is ~6 months old.

cho · #9 02-26-2015, 04:49 AM

Quote:

Originally Posted by Cinnamonandgravy

....the oil cap gasket has needed replacing ......

if not done before...you can flip it (180dg) usually it will do the trick
for next year or two

.

toomany MBZ · #10 02-26-2015, 09:35 AM

I agree with others, your engine temp is too low.

The pic is from the FSM.

toomany MBZ · #11 02-26-2015, 12:18 PM

Seems I posted the above to a different question, my apoligizes.

Maxbumpo · #12 02-26-2015, 12:54 PM

If oil is forced out the dipstick tube because the pressure in the crank case is too high, seems to me that you need to investigate the cause of the high crankcase pressure?