Hey guys, 1991 300d 2.5 turbo. Bought cheap with many problems, had made a lot of progress and almost ready to give the keys to the wife when I pull in the driveway and see a trail of oil behind the car . (please see the attached pic, it wasn't a drop or 2...it left a stream of oil).
Overnight, it leaked a 2-ft diameter circle of oil on the ground under the car. No known oil leaks prior to this.

I got under it the next day and found the oil running out from where the engine and trans join. (BTW, it's definitely oil and not trans fluid. Confirmed both by color and a stable trans fluid level, but significant loss of engine oil as shown on dipstick).

I've never seen a rear main oil seal fail this rapidly, but there's a first time for everything, right? I expected to see a visibly damaged oil seal, but upon trans removal, the seal looks ok and reasonably dry, while rest of housing is soaked in oil. (please see attached pic).

I'm still planning on replacing the seal, but want to make sure there's nothing else under here that could have caused my sudden and severe oil leak. I definitely don't feel like doing a transmission R/R again.

Thanks all for your time and help.

Best,
Brad

Attached Thumbnails

   

Any chance of turning up the brightness?

Yup, the rear seal looks dry. I'd think long and hard before touching the rear seal.

I know a 617 that leaked from one of those big BB things that caps the end of an oil gallery. But the whole bell housing flange area in your car looks dry.

The oil filter housing with the oil cooler lines and the aft end of the cylinder head are known leak sources.

Sixto
87 300D

Did you perhaps just change the oil and not seat the oil filter cap o-ring properly?

Sixto
87 300D

Sorry, this was the best pic my cell could take.

I changed the oil about 1000 mi ago.

I've changed more than my fair share of oil cooler lines...definitely not coming from there.

I feel 99.9% confident that oil is not running down the engine and dripping off at the bottom. Oil is leaking from inside/between the engine and trans. I spent a lot of time confirming leak location prior to teardown, cleaning everything off with compressed air and brakecleaner.

Still accepting input to make sure this thing gets fixed right the first time!

Thanks,
Brad

Oil filter stand gasket?


Or the back of the valve cover gasket has a little dip in it like the front does, if that isn't seated right they leak pretty good too.

__________________
68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

I brightened the picture on my PC. The starboard half of the picture looks dry. The port half is still dark. I just don't see pools or trails of wetness. Maybe you cleaned it before taking the picture?

You know, if the engine is secure or if you can secure it as it is in the picture, start the sucker and run it until oil drips, pull the ring gear and look for the leak.

Sixto
87 300D

Is the rear main in this engine replaceable in situ?

__________________
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

Yes.

Sixto
87 300D

If you know anyone with an automotive repair shop, see if they have a smoke generator you can use and find the leak the first time.

__________________
'83 300D, 126K miles.

I don't have a repair shop but until I get the turbo resealed my car is a heavy foot from being a smoke generator

Sixto
87 300D

In adding a smoke machine to an engine ,were would it be hooked up ,the oil cap?Ive got a very similiar leak in a 2.2 ,like to hear the outcome of this mystery leak .The oil would be drained first, right.

The dipstick tube, after sealing off the filler on the valve cover.

__________________
'83 300D, 126K miles.

And the valve cover vent hose?

Sixto
87 300D

there's also a dye test

Forgot that one. The dye test is good also, but will require that the engine be reassembled and run.

__________________
'83 300D, 126K miles.