Nightmare leak from hell

[blocke]

I am at the end of my rope chasing this leak. Appreciate any direction you guys can give.

Background: Pulled my transmission a few weeks back to replace a leaky input shaft seal. I did not touch anything on the engine side. Clutch, PP and FW stayed in place.

2 days after fixing the input shaft seal, oil starts dripping from inside the bell housing. At first it was just 1-2 drops. After about 100 miles of driving, my clutch started slipping at 4k rpm. So I assumed the rear main seal (replaced just 1 year ago) had let go.

Dropped the tranny again this past weekend, examined rear main seal. It looked fine, back of the block was clean from the head down. I cant see any cause for the leak. Just to be safe, I replaced the rear main seal, the cover gasket, clutch disk and pilot bearing. Put everything back together.

Drive to work Monday (100 miles round trip), car was fine. Park car in driveway and let it sit for 4 hours. Came back to check under car, and it looked like the BP oil spill in my driveway. HUGE oil slick. Oil is dripping out from inside bell housing again.

WHAT THE FUCK? I'm stumped on where it's coming from. The only thing I have noticed is that it looks like my car has the classic head gasket oil leak at the rear cylinder. Could this be running down inside bell housing? There was no oil trail coming from top of engine.

This all occurred after removing tranny. I dont know what I could have done to cause this when I didn't touch the engine side of things the first time around.

[Sagaris]

Do you have your crankcase ventilation tubefrom the valve cover capped off/blocked off/modified? I know that it is unrelated to the input shaft seal, but it can be the cause of strange oil leaks elsewhere. Also, I am not familiar with the transmissions but is there a vent port on the top of the trans?

[blocke]

Do you have your crankcase ventilation tubefrom the valve cover capped off/blocked off/modified? I know that it is unrelated to the input shaft seal, but it can be the cause of strange oil leaks elsewhere. Also, I am not familiar with the transmissions but is there a vent port on the top of the trans?

No mods to crankcase vent, it's new actually. And G260 does have a vent up top, but I checked that too when fixing input shaft leak. It's functional.

[Zba]

Is the leak gear oil or engine oil? Is it possible you gouged the seling surface when you pulled out the old input shaft seal? Is the seal installed correctly, ie: not folded over, crushed or trapped anywhere?
It's a long shot, but did you feel any vibrations in the upper rpm range while driving?

[Sagaris]

It's a long shot, but did you feel any vibrations in the upper rpm range while driving?

What does this indicate/where are you going with this? (honest question)

[blocke]

Is the leak gear oil or engine oil? Is it possible you gouged the seling surface when you pulled out the old input shaft seal? Is the seal installed correctly, ie: not folded over, crushed or trapped anywhere?
It's a long shot, but did you feel any vibrations in the upper rpm range while driving?

Nope, not tranny fluid. I have fresh redline in it, so the leak would be pink. My oil is due for a change, so its nasty black. Im sure its oil.

[Zba]

What does this indicate/where are you going with this? (honest question)

I purposefully left my reasoning out so as not to raise any flags with the op. I've seen bent cranks (actually just one, non BMW) where there was a vibration and a massive oil leak at the rear main. The car exhibited symptoms of a misfire, accompanied by an oil leak. Seemed easy enough and I even measured the crank bore which was in spec. BUT, if you spin the crank 180 out, voila! Bent crank and an out of spec crank bore.

[Sagaris]

I purposefully left my reasoning out so as not to raise any flags with the op. I've seen bent cranks (actually just one, non BMW) where there was a vibration and a massive oil leak at the rear main. The car exhibited symptoms of a misfire, accompanied by an oil leak. Seemed easy enough and I even measured the crank bore which was in spec. BUT, if you spin the crank 180 out, voila! Bent crank and an out of spec crank bore.

I have an RPM related vibration that I am trying to workout which is why I asked, that's pretty wild though! blocke, have you considered using a UV leak detection kit? I got one on Amazon with a UV penlight for a really decent price, the light isn't the best but it would be a more reliable way to determine the source than trying to see around corners in the engine bay.

http://www.amazon.com/s/ref=nb_sb_ss_i_5_17?url=search-alias%3Dautomotive&field-keywords=leak+detector+kit&sprefix=leak+detector+kit

[blocke]

I have an RPM related vibration that I am trying to workout which is why I asked, that's pretty wild though! blocke, have you considered using a UV leak detection kit? I got one on Amazon with a UV penlight for a really decent price, the light isn't the best but it would be a more reliable way to determine the source than trying to see around corners in the engine bay.

http://www.amazon.com/s/ref=nb_sb_ss...k+detector+kit

Yeah I was contemplating that last night. I was also contemplating a complete rebuild. Ive dropped the tranny 4 times for various reasons.
Is this headgasket leak thing common?

[Zba]

All I can say is go over all of your work with a fine tooth comb. Did it really only start puking oil after you had the trans in and out, or has it always been there? I don't have an M20 or an E30 for that matter but the above question about breather lines/connections/seals all being present and intact is a valid one.

Is there oil on top of your trans, or are you sure the leak originates from inside of the bellhousing?

[blocke]

I'm positive the leak wasn't there before removal of the tranny. The outside of the bell housing is squeaky clean, i hit it with Gunk and a pressure washer when I had it out. That's the confusing part. No external signs of a leak, when it was apart there was no internal evidence. But now that its back together, its dripping from inside. Also, the fact that my previous clutch disk was soaked in oil and slipping tells me its either originating inside, or its getting inside the bell housing somehow. So confusing.

[tommye]

Ive had engine oil dripping from bell housing on 2 m20's.
Both times it have been the oil pan gasket.

[blocke]

Ive had engine oil dripping from bell housing on 2 m20's.
Both times it have been the oil pan gasket.

That is something to check I guess. Isn't there a cover of sorts that mates to the bottom of the tranny, and covers the back half of the oilpan? To inspect the clutch?

[tommye]

Take off the cover and you will probably see your problem.

[Cabriolet]

did you change the oil pan gasket when you did the front and rear seals?

it breaks that gasket's seal when you change out that stuff.