E300D mystery oil (leak) - PeachParts Mercedes-Benz Forum

landev · #1 03-18-2018, 10:14 PM

My E300 has developed an oil leak that has me completely baffled. There is oil on the intake tubing that leads from the front grill to the air filter box (none in the box, thank god!), also oil sprayed on the two vacuum switches below the air box, dripped on the lower radiator hose, and the front right corner of the air box. There is also oil pooling on the interior chassis wall below the passenger headlight. It seem to be being spread by the radiator fan, yet the fan has no oil on it. It also seems odd that there seems to be no oil splattered anywhere near the block, nor out the dipstick tube, etc.... just on the far left of the engine compartment near the air box.

Seems to me that all the plumbing located near the air box is either vacuum or engine coolant. So, where's the oil coming from?
I see no drop in oil level, but it is certainly engine oil. It is also on the wrapped wiring that runs along the bottom of the radiator, i.e. in front of the radiator! Damn Peculiar!

As near as I can tell, there are no coolers (i.e. transmission or oil) around the radiator... just the radiator for engine coolant.

I've cleaned the oil off, run the car (from cold start) and see no weeping anywhere. Perhaps this is an "under load, hot engine" issue.

I'll be buggered if I can't figure this out. Anyone seen anything like this? If so, where's it coming from?

Thanks much in advance!

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sixto · #2 03-19-2018, 01:09 AM

There should be transmission cooler lines attached to the passenger side radiator end tank.

There’s a power steering cooling loop but the fittings are on the driver side.

The AC evaporator is ahead of the radiator but AC system like is very light.

If the clutch fan is spraying engine oil, it might be from the vacuum pump.

Sixto
98 E320s sedan and wagon

treetops · #3 03-19-2018, 01:27 PM

The only oil related part in that area I know of is the crank case vent tube, but that goes into the intake after the air filter. If it were disconnected it would drip oil. That oil could then be flung around a good bit by air flow around the engine bay at speed. Just a thought.

landev · #4 03-19-2018, 01:40 PM

Thank you for the responses!

Sixto: I thought of a transmission cooler issue, however with the limited crawling around I did I could not find any cooler other than the radiator. I checked the transmission fluid level... no change. Also, the oil I'm seeing is very dark in color with no trace of redness... I'm 95% sure it's engine oil... just in a very odd location. No oil on the fan blades, vacuum pump, or anywhere on the engine-side... just on the air intake tube, vacuum lines, and the top of the lower radiator hose.

Treetops: this sounds more like what might be causing the issue, but I cannot find any loose lines. The pattern of splatter looks like oil is slowly dripping from directly behind the fan and being directed towards the front passenger side of the engine compartment.

I just ordered a Rigid 40043 inspection camera to help sleuth this one out. A good occasion to justify a tool I've always needed/wanted!

Thanks for your help. Will keep looking...

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sixto · #5 03-19-2018, 10:33 PM

AFAIK the 606.910 valve cover breather goes to the intake manifold, not the air intake. For kicks, see if there’s oil in the accordion tube between the air cleaner and crossover pipe.

Isn’t the 1/2” metal line that goes over the radiator a transmission cooler line?

Sixto
98 E320s sedan and wagon

landev · #6 03-20-2018, 07:03 PM

Sixto: No oil in the air intake hose. I checked this first... was worried about blow-by... it's dry. I'll have to look again for a trans cooler line when I go back down to the shop.

I wiped the oiliest bits off before doing my commute this morning. When I arrived back home (~70 miles) there was again the splattering I've grown to loath. I'm attaching a photo looking straight down at the lower radiator hose. New oil looks like it's dripped on the lower hose... but from where?

I ran the car at ~ 2200 rpm and watched for seeping or anything... don't see a damned thing!

As the picture tries to show, there is splatter on the vacuum switches below and to the right of the air box. There is also oil splattered on the intake tube to the air box as well as the lower front right corner of the box.

Again, the fan has no oil on it and there are just minor spits of oil near the block that look like splashing.

I'll be damned!

Thanks again!

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t walgamuth · #7 03-20-2018, 08:27 PM

looks pretty clear.....power steering if it is....I suspect.

Jeremy5848 · #8 03-21-2018, 01:15 AM

Quote:

Originally Posted by sixto

AFAIK the 606.910 valve cover breather goes to the intake manifold, not the air intake. For kicks, see if there’s oil in the accordion tube between the air cleaner and crossover pipe.

Sixto
98 E320s sedan and wagon

The engine in a 1996 E300D should be a 606.912, I believe, at least that's what's in mine. The oil-to-coolant heat exchanger is on the driver's side, near the oil filter canister, so it can't be the cause. The crankcase vent splits into tubes that connect to the intake manifold but again, that's on the driver's side of the engine. I can't think of anything other than a loose engine oil dipstick tube that would be the source of oil at that right front corner of the engine.

Jeremy

Jeremy5848 · #9 03-21-2018, 01:17 AM

Quote:

Originally Posted by t walgamuth

looks pretty clear.....power steering if it is....I suspect.

Power steering pump is on the other side (driver's side) of the engine.

sixto · #10 03-21-2018, 01:44 AM

Chain tensioner?

Sixto
98 E320s sedan and wagon

Maxbumpo · #11 03-21-2018, 09:38 AM

Quote:

Originally Posted by sixto

Chain tensioner?

That was my thought as well, a squirting spraying pin-hole leak from the chain tensioner could spray into the area in the photo.

Dipstick seal leaking is also possible.

Another possibility would be a failed headgasket, but I've never heard of one in that area.

Lastly, the front crank seal, but that would also spread oil along the bottom of the engine.

landev · #12 03-21-2018, 01:31 PM

Thanks all for the input.

t_walgamuth: PS actually was one of my first suspicions. I discarded this (may need to re-investigate) as I replaced the rack ~ 4 months ago. I know it's not coming from the pump or supply lines as they are indeed on the other side of the engine, but possibly a failed rack could be somehow squirting fluid up? Seems like a long shot, but worth a look when I get time this weekend.

Jeremy_5848: Due to the visible drips, it sure looks like the source should be the dipstick tube. No oil on the upper portion... I'll check the lower this weekend.

Sixto/Maxbumpo: I've been suspicious of the chain tensioner but don't know the physical construction specifics of the unit. I've noticed oil inside the large hex-keyed portion but assumed that this was just spray from elsewhere. Cleaning it off before driving shows that after my commute, there is a small bit of oil again either emanating from or splashed into the hex-key interior of the tensioner.

Not knowing what the cross sectional view of the part looks like, I was assuming that it was a fairly solid construction that no oil should be oozing from... perhaps I'm wrong on this?

Thanks all!

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t walgamuth · #13 03-21-2018, 01:41 PM

what color is the oil leaking out?

landev · #14 03-21-2018, 02:02 PM

Looks like dirty engine oil. Don't know if the "dirty color" is from the engine compartment or if it is indeed engine oil. I'm fairly certain it's not transmission oil... no red tinge at all...

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landev · #15 03-24-2018, 07:51 PM

OK... it appears that Sixto hit it on the head. I wrapped the chain tensioner in paper towel, then aluminum foil and then secured it with a zip tie. I did the daily commute and just checked. No oil on the outside of the foil, but some dripped below the tensioner. I cut the zip tie... the paper towel was soaked with oil and it dribbled from the foil.

Who'd a thunk it? I'd never of guessed that oil would be leaking from that solid looking item.

I ordered a replacement and will install when it arrives. 'Will need to figure out how to tension properly, but there's a sigh of relief from Idaho... seems like another bullet thus dodged!

Thank you all for your help and ideas on this. I was completely baffled!

Best!

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