'94 W124 104 bad oil leak rear engine - VERY FRUSTRATED - PeachParts Mercedes-Benz Forum

RamahX · #1 02-06-2012, 01:14 PM

'94 E320 W124 M104 with 168,000 miles. Daily driver. Still runs reliably, but this oil leak has me bewildered.

History of this leak - See this post and this one and these pictures and video of leak. (these are all before pictures, everything is clean now. Sorry for the rabbit trail

) Originally thought/assumed it was rear main seal.

Removed oil filter stand and cleaned, replaced gasket. Polished up all surfaces mirror smooth.

Filled with oil, buttoned up and started, and LEAK IS STILL THERE AND FILLING UP TRANSMISSION BELL INSPECTION PORT. Only this time its new oil, not old.

Oil is running down drivers side of the bell housing - SAME PATH.

WHAT is on the rear drivers corner that could be doing this? Leak is a significant one. It's very difficult to inspect even with a mirror.

Since I've super cleaned EVERYTHING plan on getting back under while running to see. After reviewing the oil flow diagrams I really don't see head or other oil galleys in that back corner. And even if it was the head gasket, oil would run down to the oil pan while parked, but this oil continues to stream while running, but continues to drip/seep out all night (alot!). So either the oil filter's backflow check valve is keeping the oil filter unit pressurized, or its the rear oil pan... aggghhhhhh

My next suspicions are:
1. Could the POSITION SENDER UNIT-HFM (part no 003 153 01 28) leak oil?
2. check the oil filter housing CAP. It has a new (dealer) filter and gasket, but maybe its cracked.

hanno · #2 02-06-2012, 03:32 PM

Is the valve cover gasket properly seated/positioned at the rear of the engine? you "may" be able to see it with a mirror. It sounds like way too much flow when running to be the head gasket.

Hirnbeiss · #3 02-06-2012, 05:23 PM

So there is a big leak in addition to the oil level sender leak?
The only things that come to mind in the upper drivers' area are the the filter and housing, valve cover gasket corner, and headgasket corner. You might get your best view putting the car up securely on ramps / jackstands, lying down and looking up with a flashlight.

hanno · #4 02-06-2012, 05:46 PM

Additional to the valve cover gasket...your #2. "check the oil filter housing CAP. It has a new (dealer) filter and gasket, but maybe its cracked". I doubt the cap is cracked, but it can certainly leak if the o-ring got rolled, pinched, or cut.

how long after new filter did it start to leak?

Keep us informed.

RamahX · #5 02-06-2012, 10:46 PM

OK... Its not as bad as I thought this morning. Got some oil dye and ran the engine.
Apparently I had 2 bad leaks, and I've repaired the first one, which was the oil filter stand gasket. After running its all still bone dry and dye shows NO oil there or anywhere, including the head and valve cover gaskets. This knocked my oil leak puddle down by half or more.
However...
Dye is showing oil streaming from back oil pan bolt drivers side. Bolt is stripped and finger loose. Oil is running out that and also inside bell housing same vicinity.

How do I fix this? Thinking of getting a longer bolt and also injecting with JB Weld or something that will seal even with oil residue.

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deanyel · #6 02-06-2012, 11:47 PM

It sounds like your oil pan has been off and reinstalled poorly. If it's just leaking from that bolt hole and not from the seam I'd just try to seal the bolt threads with something like Permatex Thread Sealant, available at pretty much any auto parts store. But you've got to drain the oil and get it all clean first, and then don't put the oil back for a while. If the seam is leaking because the bolt isn't performing you could try Heli-Coiling it. You want to try to avoid oil pan removal - big job.

Permatex 56521 | Thread Sealants

Hirnbeiss · #7 02-07-2012, 07:44 AM

Good detective work, Chief.
On the oil pan bolt, you can try retapping with the current thread size first to see if that gives you enough thread back to hold the pan. If not, a threaded insert like Helicoil would be the next step. Sealant goop alone probably won't work for long because you need something to pull up othe pan corner.
If you don't want to buy/do the Helicoil yourself, any decent mechanic can do it for what shoudl be a reasonable fee.

RamahX · #8 02-07-2012, 03:03 PM

Here are pictures of the leak as it stands now.

Ultraviolet Dye leak at rear drivers side oil pan bolt

Leak at rear drivers side oil pan bolt

And yes, car's been up on ramps with safety jacks for 2 weeks now, and I've already repaired all oil sensor gaskets (which were leaking also).

Other side. Note euro car jack added for 3rd safety. Wheel Chocks are on both rear wheels also.

Hirnbeiss · #9 02-07-2012, 05:40 PM

Good to see that your keeping your priorities in order and remembering to drink plenty of Hefeweizen (Paulaner).

RamahX · #10 02-07-2012, 10:13 PM

Don't forget the Oktoberfest Wiesn litre...

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RamahX · #11 02-09-2012, 10:02 PM

OK... replaced one of the oil sump (pan) bolts (M6x85) with a slightly longer one (it was stripped) and that worked - its one of the two inside rear oil pan bolts that actually bolt to the rear main seal/rear cover (MB nomenclature).
Its mate on pass side was replaced before (unk when) with a SAE bolt with coarser threads - meaning THAT one was stripped in the past - so SOMEONE has been here before...

Using fluorescent dye there are no more oil leaks OUTSIDE but its STILL leaking inside the bell housing ALOT and running out flywheel locking port.

At this point I don't know if its the radial shaft seal or the rear oil pan gasket.

I read that there is a repair seal. Also MB manual states end cover with integrated radial shaft seal should be replaced with end cover with 'press fitted radial shaft seal...

Help...

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