Oil cap leak/spray or crank vent?

[Som]

My story:

Driving up to LA from San Diego and about halfway up I notice my hood is fluttering a bit on the right side like I didn't close it all the way. Apparently just pressing on the logo isn't always enough to close both latches anymore. I pull over at the next exit and, after closing the hood all the way, I start smelling burning oil.

Pop the hood, and the entire passenger side of the engine is covered in oil. I look around, and the entire right front wheel/brakes are covered in oil as well as drops along the passenger door.

• 2009 E92 M3
• Old style oil filler cap
• I'd screwed it on so that it was "upside down" -- i.e. the oil symbol on the cap was facing away from me.

So I thought, "maybe I just didn't tighten this all the way" or "maybe the cap orientation really does matter".

• I clean off all the oil around the filler
• I replace the cap in the "correct" orientation
• I make sure it's on nice and firm

Before even attempting to drive it again, I want to see if it'll leak. So I start the engine and rev it up and down a bit, hold it at around 4k, etc.

• More smoke from the engine
• Small flame on the exhaust manifold
• I blow out the fire as fast as I can (yes, I was freaking a bit here. yes, I realized this was a risk when I saw the leak.)
• Oil cap has a fresh trail of oil dripping down from it.

So I get towed and start reading up on the oil cap issues. I also inspect the head/valve/cam cover and it appears to have the same bubbling/flaking issue that many people have reported. So it's possible this has caused a problem with the sealing of the cap.

Problem is, while there are a lot of threads about excessive leaking, there only a few mentions of the "explosive oil diarrhea" incidents.

There are also some mentions of a crankcase breather/vent/valve/hose that can get clogged. Unfortunately, beyond these random mentions, I can't seem to find any more information about what this part is, how it gets clogged, and what the symptoms are. I've been changing my oil at the 15k intervals with Blackstone testing at each change. The test results appear to be okay, but I'm wondering if the long interval could be exacerbating this clogging issue. It's also possible that those mentions were only in E46 related discussions and I didn't notice that while searching (a lot of the results get intermixed).

I'm concerned that if I simply change the oil cap, then, if there's an actual crankcase pressure problem, I could be triggering an issue somewhere else.

Does anyone have specific experience with the crank breather clogging issue? Is this an actual problem on our cars? Can it cause an other-wise functional oil cap to spray all over the engine as I've described?

Any help would be appreciated!

As a note -- yes, I'm incredibly lucky that my hood hadn't latched all the way. If I hadn't pulled over to close the hood all the way I almost certainly would have seen my car burn to the ground when I hit the typical LA traffic (unless someone around me had an extinguisher -- which my wife and I were just talking about purchasing for our cars less than a week ago).

Som

Photos of the cap, valve cover, and engine bay:


No obvious deterioration of the seal, though it's certainly not clean of debris. Doesn't like it would be enough to cause all that spray, but maybe?


Hard to see, but there's actually a little powdercoat bubbling on the right side of the hole. I could see this as being a source of a leak, but the spray/leak seemed to come from almost the opposite side of the cap -- so I'm reluctant to think it's the sole culprit.


I'd already done some cleanup before this photo was taken. There's still oil all over the frame rail/coolant tank/fuel rail/wheel well.

[SUBFRAMERIPPER]

That is a long post. Before the leak was the oil cap removed? It is well known that when you remove the oil cap you do not turn it upside down. If you do you will be cleaning up oil in your engine bay.

[Som]

Heh, sorry for that. Figured there were a lot of details.

Anyways, yeah, I had just added a quart and had put the cap on "upside down" (oil fill symbol facing backwards). I didn't think much of it when I did it -- and even intentionally told myself not to succumb to the OCD of having to have it face the right way and leave it be. :|

I read somewhere (today, after the incident) that the orientation mattered, but the post wasn't definitive about it. Is there a thread covering this? It seems odd that the cap would be directional, but it would certainly be an explanation for what happened here. I'll do some more searching on cap orientation.

Thank you!

Som

[SUBFRAMERIPPER]

Not upside down like that. Upside down like you have
it in that first picture with the bottom facing up so you can see the gasket. When you do that oil seeps behind the gasket and you will not get a proper seal. Best bet is to remove cap and gasket, clean off all oil. Make sure that both are completely dry then put everything back.

[Som]

OOOOOOOH.

Didn't realize that could be a problem. I think I've always laid the cap down upside down while adding oil to prevent it from picking up debris from other parts of the engine bay.

Could the leak caused be so much as to spray all over the engine bay like that? I lost about half a quart in about 45 minutes of driving (going by the computer's oil level indicator).

Som

[SUBFRAMERIPPER]

Yes. Been there done that.

[monterey]

15k miles is a long time. I changed mine at 8k and the bottom was so sludgy. Even though my blackstone report said i can go to 10k, i think 6k is the longest i want to go.

[GVIFlyer]

There's a campaign on the oil cap.

[Helmsman]

Originally Posted by monterey

15k miles is a long time. I changed mine at 8k and the bottom was so sludgy. Even though my blackstone report said i can go to 10k, i think 6k is the longest i want to go.

First stuff coming out was sludgy Monterey, or did you remove the pan to have a look?

Cheers

[kb9uwu]

Originally Posted by monterey

15k miles is a long time. I changed mine at 8k and the bottom was so sludgy. Even though my blackstone report said i can go to 10k, i think 6k is the longest i want to go.

BMW says 15k, but what do they know?

[krx927]

This also happened to me. The spillage was as big as yours. I had oil also on the right wheel and brakes. And a lot of oil in the engine bay.

For me it started when driving on a track day. Unfortunately I did not notice it and I did the whole track day like that and the car did not catch fire

I discovered it only days after when changing tires. It was the oil cap. When I checked the seal I saw that it was not sitting properly. I just bought a new cap and it is fine now.

I must say that I do not have this bubbling of the powder coat issue.

For me it never happened again. And I am also not putting the cap upside down when adding oil.

Bottom line; for me it was just shit that happened once.

[///M Power-Belgium]

Originally Posted by Som

OOOOOOOH.

Didn't realize that could be a problem. I think I've always laid the cap down upside down while adding oil to prevent it from picking up debris from other parts of the engine bay.

Could the leak caused be so much as to spray all over the engine bay like that? I lost about half a quart in about 45 minutes of driving (going by the computer's oil level indicator).

Som

Som , here you go => http://www.m3post.com/forums/showthread.php?t=704497

[Som]

Wow. Long post wiped out by accidentally hitting Ctrl-W instead of Shift-W. Guess I type too much.

Anyways, just wanted to update this.

I left the car sitting for a couple days. I knew I wasn't going to go crazy reaching every part of the motor, so I'd let as much of it drip/drain off as I could manage.

I cleaned the engine bay with a spray bottle of 1:1 Simple Green/water solution, let it sit for a few minutes, and then rinsed it off with a spray bottle of water. Didn't want to go the hose route -- not comfortable with that. Avoided spraying electrical connectors, but didn't cover anything up or anything like that. Dried everything I could reach with a rag. I'm sure some areas under the plenum were still wet when I was done, as well as some of the areas far back on the frame rail. I just tried to rinse these parts as much as possible to dilute any of the Simple Green.

Took the o-ring out of the oil fill cap and cleaned it off by spraying it with WD-40. Cleaned the cap where the o-ring sits with the Simple Green solution and water rinse. Dried both. I squeezed the two metal prongs to help get a slightly tighter seal, but I didn't push too hard -- so it's possible they ended up in the same spot they started. Replaced the cap.

Then I left the car for another couple days to let any of the water I'd sprayed in the engine bay to dry out.

Drove it until it barely warmed up. Ate dinner. Drove it home. Let it idle and then revved the engine several times to 5-7k, then held it around 4k, then 5-7k again. Basically the same routine as the first time. The first time I did this rev test I got a nice wide drip of oil down the from the oil cap. This time I got nothing -- totally dry.

Of course it's still possible there's an issue, so I'll keep monitoring, but so far so good.

Thanks for the help, SUBFRAMERIPPER. Everyone else, too. Hopefully this fix takes.

Som

Edit: Week later, few more drives later, still bone dry from the cap.