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Was under the m535 yesterday....nice and hot... and I noticed a leak coming from the bell housing area. Fresh oil dripping off the bottom. In the past I have always thought it would be the rear main seal. Is it possible there is something right behind the head area that could leak oil. I see a little cover plate and it is not leaking and the oil sensor is dry. The top of the bell housing is wet also, so I am thinking valve cover. However, it is a lot of oil for the valve gasket to be the problem.
Any ideas?
jm

You said 'a little cover plate'. There's a duck bill plate on the back of the motor that's hard to get to, somewhere next to the head. I've heard this leaks after awhile, of course, but no one remembers it.
I also heard, the engine needs to be out to get to it!
Good luck,,,,Greg

Do you mean the little metal plate right under the valve cover in the back of the head? It seems to be right up against the fire wall....so yes, having the engine out would make it a lot easier to get out.....
thanks for the reply,
jm

That little plate has an unusual gasket. One (1) of the washers used on the retaining fasteners is special and has a rubber seal on it.

Here is what the gasket looks like:



Based on the above photo, you can probably guess which hole gets the special washer.

I believe that the special washer is bmw part #12110002735.

I mention this because I could see how someone could easily over look this and leave that sealing washer out.... resulting in an oil leak.



You may be able to get a mirror back there to see if it is your source of oil.

Hey that picture was very helpful. I could not that good of a picture. I will check it out with a mirror in the morning.
I was also thinking it could be the valve cover, so I will check that out too; but if it is something more serious, I will have to wait until I find out about the suspension.
thanks for the help, will post what I find.
jm

Thanx, Blaise. It really DOES look like a duck lookin' left!!
I guess this is the one people mean?
Also, is it that I can't see the forest for the trees?
I see two holes that maybe need the special washer.

OOHHH! Is it the duck bill, 'cause it's out there by itself?? ?

Great design, I wonder what the reason behind this could be.
Mine was leaking, and now I understand why.

GripGreg wrote:Thanx, Blaise. It really DOES look like a duck lookin' left!!
I guess this is the one people mean?
Also, is it that I can't see the forest for the trees?
I see two holes that maybe need the special washer.

If I understand correctly, this special washer is used on the only hole that is not isolated from the oil galley by the gasket (left most in photo). The oil would be in contact with the bolt shaft, hence the need to seal the bolt head.

Bumping thread. I own the car now and it still has this issue. In doing some research prior to posting, I came across a few threads that indicated that the head bolts may not be tight enough. So today, I took the valve cover off and with a torque wrench, followed the pattern of:

Firewall Top: 14 10 4 2 6 8 12
Firewall Bottom: 11 7 5 1 3 9 13

I started at 32lb ft based on this thread for a 528i
http://www.firstfives.org/bboard/viewtopic.php?t=1033, then went to 59lb ft. None of the bolts so much as twitched, so I bumped the wrench up to 74lb ft. I had seen a thread on mye28 where someone had used the M5 specs of 74lb ft. So I did that and the only 2 that budged were 14 & 11 (the back where the leak is coming from). As with before, the rest did not twitch. The results are that the volume of oil being leaked there (I washed it all off and went for an hour drive, some city, some highway), has been drastically reduced, but its still leaking.

My question is, what is the proper torque for the head bolts on a 1980 M535i? I'm worried about over-tightening it. Thanks for any assistance and I apologize for asking, but I haven't found a Haynes or any other manual specifically for this car yet.

Edit/Update, I found this: http://www.malloc.nl/BMW/635CSi/pages/en/11121000.html which is saying the torque specifications for the engine are:
Tighten bolts in three steps:
Step 1 - 34 to 44 Nm (25 to 32 ft.lbs.)
Step 2 - 67 to 71 Nm (49 to 51 ft.lbs.)
Step 3 - 75 to 81 Nm (54 to 59 ft.lbs.)

So if 59 ft.lbs. is the proper torque, how hosed am I? Do I loosen all the headbolts and then tighten them back down to 59?

I'd leave them. I don't recall ever hearing about a broken one, so while I probably wouldn't have done it, I see no harm. I actually did way overtighten head bolts one time trying to limp a car with a blown headgasket home. But it didn't matter how much I cranked on them I wasn't going to straighten out that warped head. It didn't do any good, but no additional harm I could tell.

I checked it again yesterday evening and there was hardly any oil, significantly less even than when I posted the question and bumped the thread. So the tightening appears to be a success! Thank you for the response!

Out of curiosity, is it really that hard to change this gasket? Do you have to remove the head to do it? Are the bolts too long to be able to exit with the head still attached? Mine is leaking a bit. Fortunately 85% of the leak appears to be from the oil pressure switch and changing that helped. Just wondering how big of challenge changing this seal and gasket actually is with the engine still in place.

Sorry, please clarify. The head bolts are just under the valve cover & gasket, so is that what you're referencing? The task of tightening them down is super easy since you just remove the valve cover and then use a torque wrench on the 14 larger size bolts in the pattern I list above. I found the hardest part of the whole process to be getting all of the connections/nuts/bolts off of the valve cover itself and making sure to put them all back on in the proper order/place.

So if you're talking about replacing the head gasket itself, that's a whole other beast (IMO). My leak is almost non-existent now and short of pulling the head off and having it straightened (as per Mike W.'s response), I'm just going to live with the little bit it does leak. When its time to have the engine rebuilt, I'll have it done right then.

Was referring to the duck gasket/cam shaft cover on the back of the head facing the firewall. Have no intention of pulling the head to replace the head gasket. My duck gasket/cam shaft cover appears to be leaking a bit, but nothing crazy.