Mystery Oil Leak

[CBlake]

Hi all-
New to the forum and new to BMW's as well and I'm looking for a little help on an oil leak.

This is the back of the engine on my 1997 M3 Sedan... First I replaced the head bolts since the head was recently replaced. Next, I put on a new valve cover gasket with silicone in the right places, waited 2 days, and still had the leak. Then, I replaced the valve cover rubber washers and still have this leak, so I replaced the entire valve cover. Still leaking... Does this point to rear main or head gasket?

There's not that much back there that can leak...

Thank you!

[hide1]

Sounds like it might be the RMS. Does it smoke..? Has it ever been replaced?

[CBlake]

No smoke at all...

I don't know about the RMS. The guy I bought it from didn't mention it and had done a lot of work to the car, so I doubt he did it. From what I've read, the RMS looks easier to change than the head gasket (which only has about 1000 miles on it).

[NoLastName]

A leaking rear main seal won't put oil that high up on the block. When my engine started dripping down that same path it was the valve cover leaking because the rubber grommets on the hold-down bolts were toast. Of course you've already replaced the grommets and the VCG, so unless you've botched that job they're probably ok. The oil really appears to be coming from the cylinder head area, so from head gasket up to VCG is where I'd be looking. There are really only a couple places oil can come from in that location.

Something to check: there's a threaded plug with aluminum sealing washer on the back of the head casting. It seals up the main oil galley in the head, and it can leak if the plug comes loose. It's the hex head bolt circled in the pic. Maybe check that? You'll probably need a flashlight and a mirror to see because it's way back against the firewall.

If it's not the oil plug then clean the whole area and look for fresh oil to come back out.

[CBlake]

Thanks for the idea. I will check that tonight. Do you know what size it is, by chance?

I have looked and looked... Before every run, it is completely oil free. These pictures are after about a 10 minute run.

[NoLastName]

If I remember correctly the hex on the bolt head is 13mm.

[hide1]

I agree, I thought more about it after posting. A RMS would be leaking underneath the bellhousing not down the block like that.

I would also throw a cracked/ warped valvecover into the list of things to check. They are plastic and get brittle with heat cycles and age. I found a hairline crack on mine around one of the mounting nuts where the PO possibly over torqued it. Now I only found this after degreasing and washing. Only then was I able to see the small crack letting light through. Filled with JB weld and let cure. Hasn't leaked since.

[CBlake]

I assumed valve cover after changing everything else, but like I said, it's brand new with 1 10 minute drive in it.

[ThreeD]

Is it oil? Or coolant? Either way it could be from a bad HG as well. Your best bet will be to do a thorough cleaning to see where a new leak springs from.

[shaft9ii]

Might be a dumb question but was the head checked for flatness to make a good flat mating surface?

[CBlake]

It is oil. These pictures are from after a 10 minute drive of a completely clean area. This is the leak that I am trying to find. There is no extra oil here. I know most people haven't cleaned an area well enough to see the source of a leak, but as you can see from the pictures, it is a very clean area, I just can't tell the source.

The head was brand new installed by the previous owner and a reputable shop, so I assume it was done correctly, but I don't know for sure.




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NoLastName- I just got a good look at the back of the head, and I don't have that bolt in mine. In the same place, there is a cast "nub", but no bolt.

[RRSperry]

I'll bite. Did you mention you replaced the head bolts? I see you said that in post 1. That could well be your answer...

Anyway, rear main seals so not leak up. You have to remove the tranny to replace it, so it's not any easier than the head...lol

[crqflier]

First I replaced the head bolts since the head was recently replaced.

This logic doesn't make sense, especially if as stated in a later post, the head was new and the job done by a reputable shop. Can't imagine anyone reusing old bolts in that situation. So I'd guess your problem is there. Only thing you haven't done is replace the HG and check the head. Before jumping through those hoops, what's the highest point where you first see any trace of oil?

[CBlake]

The leak was there previous to head bolt replacement. I replaced them because of the leak, and the leak is still there. Are you thinking it's still head gasket? (I am)

I have a lift and transmission jack, so I still believe removing the trans would be easier than trying to not break or bend the cams with head removal.

- - - Updated - - -

That back corner bolt is especially tough to get the correct torque angle, so I thought (hoped) maybe it wasn't done correctly.

It appears to be coming from the HG area. I can't see any traces of oil higher up, but it's a fresh oil change with clean oil that is tough to see. My concern was that is was running from another place, hitting the head gasket seam and then going to the low corner of the block.

I'm going to get an inspection camera tonight and run the engine while looking for seeping.

[dohcdoh]

The leak was there previous to head bolt replacement. I replaced them because of the leak, and the leak is still there. Are you thinking it's still head gasket? (I am) I have a lift and transmission jack, so I still believe removing the trans would be easier than trying to not break or bend the cams with head removal.

Break or bend the cams? How do you remove the head? Lol

[CBlake]

I never have, but from reading about it, it appears to be very tricky with the cams. It's not?

[AJLM34A]

No, it is not. The cams have grooves and do not have to be removed from the head, before removing the head from the engine block.

[CBlake]

Great! That does make it easier! Thank you

[mboor]

OP, are you sure its not your VC gasket? I know you replaced it already, but its easy to install it with the gasket out of place just a hair. so you replaced the head bolts after the new head and head gasket was installed?

[CBlake]

Pretty sure it's not the VCG. I ran my hand all around the back where the valve cover meets the head and it was dry and clean.

The previous owner replaced the head, head gasket, and head bolts. It developed the oil leak, and I replaced the head bolts again thinking that was the problem. So now I will have to put a 3rd set of bolts on if I do the head gasket.

[Stephen Max]

Sometimes you don't get the valve cover gasket seated properly in the half moon areas. I'd redo it just to be sure.

[Mr Flash]

Hi all-
New to the forum and new to BMW's as well and I'm looking for a little help on an oil leak.

This is the back of the engine on my 1997 M3 Sedan... First I replaced the head bolts since the head was recently replaced. Next, I put on a new valve cover gasket with silicone in the right places, waited 2 days, and still had the leak. Then, I replaced the valve cover rubber washers and still have this leak, so I replaced the entire valve cover. Still leaking... Does this point to rear main or head gasket?

There's not that much back there that can leak...

Thank you!

Hey there, I have an oil leak as well. It's really bad. IDK what it could be, my mechanic said that it can be from multiple places, so I honestly don't know what to do. I'm going to do an engine clean and then he'll look at it after to see where the oil is coming from.
[IMG]file:///C:/Users/Flash/Desktop/Flash/20150128_181945.jpg[/IMG]

[RRSperry]

Then there is always the Tracerline leak detection dye. Then you'll know for sure.

[CBlake]

Found it!!!

NoLastName was correct. The part that I thought was a cast "nub" on the back of the head is actually a allen head bolt. I bought an inspection camera last night and let it idle up on the lift. I could clearly see a small stream of purple oil coming out and traveling down to the head gasket seam where it would follow that seam to the corner of the head and block.

Now I just have to figure out how to get to it...

[hide1]

Whoa I have never heard of that before. That's a sucky place to have to get a ratchet and hex head in. Let us know how it goes..!