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Discussion Starter #1
Hi everyone, I got my 2000 M5 less than a month ago!

I have posted about rust prevention methods earlier, but now I am concerned about a different problem.

Since our motors are just as expensive to repair as rust on undercarriage, after passing a few Honda Civics I opened up the hood to maybe check for engine oil level.
I noticed a weird, never-seen-before-on-S85 type oil leak.

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It is almost like oil was raining under the hood. The plenum cover is wet with oil, the battery terminal cover is partially wet (maybe because of the valve cover gasket?)

I knew that the valve cover gasket wasn't so good since the PPI on the car mentioned oil was leaking a bit.
But it seems weird how much oil is on the plenum cover.

I originally bought the car with original square-shaped engine oil cap, but after some searching I changed it with an E46 oil cap, doesn't seem to help a lot.

Any input is welcome! Sorry if the picture sizes are too big, I never posted pictures on this forum before.
 

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I would guess the oil cap or oil separators are leaking under crankcase pressure, blowing up onto the underside of your hood and coming back down on the plenum.
 

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The vanos unit has some very high pressure lines that can fail and start to leak. They start by spraying very fine or even a mist. Even though the leak is small with the pressure so high the volume is high. Because it is a fine stream sometimes it can be hard to see. Look at the hood insulation and see if it is hitting that then dripping down, next cover these lines with paper towel or wrap them. You need to secure it a bit or the fan will blow them off. Follow the lines and you might find a spot soaked in oil which will give you a better clue.
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Discussion Starter #4
The vanos unit has some very high pressure lines that can fail and start to leak. They start by spraying very fine or even a mist. Even though the leak is small with the pressure so high the volume is high. Because it is a fine stream sometimes it can be hard to see. Look at the hood insulation and see if it is hitting that then dripping down, next cover these lines with paper towel or wrap them. You need to secure it a bit or the fan will blow them off. Follow the lines and you might find a spot soaked in oil which will give you a better clue.
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After some search on RealOEM, that seems like the line connecting on Pressure Accumulator?
The bottom lines are also connected to the assembly for VANOS I suppose. I really hope this isn't a VANOS issue

Since relieving some pressure in the line would help from leaking, instead of replacing the VANOS, would replacing the oil separator (a.k.a. PCV?) fix the problem like 95naSTA said?
https://www.ecstuning.com/b-assembled-by-ecs-parts/oil-separator-valve-service-kit/11151406788kt2/
Parts some pretty cheap and the Labor should be between 1~1.5 hrs as I have done something similar on the S85.

Would Daily Driving the car be okay at this situation? I'm worried I will further damage the motor.
 

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Take the top off the plenum, is there a significant puddle of oil? The front of the plenum looks pretty evenly soaked like it's coming from there. There is an oil drain from the plenum to the bank 2 timing cover. Leaking vanos solenoid on that side can cause oil backflow into the plenum. There's an old thread showing how to differentiate between forward flow and backflow of oil into the plenum, I will see if I can dig it up.
 

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Discussion Starter #6
Take the top off the plenum, is there a significant puddle of oil? The front of the plenum looks pretty evenly soaked like it's coming from there. There is an oil drain from the plenum to the bank 2 timing cover. Leaking vanos solenoid on that side can cause oil backflow into the plenum. There's an old thread showing how to differentiate between forward flow and backflow of oil into the plenum, I will see if I can dig it up.
I will take a look later today, I hope I don't see any puddle inside the plenum, that would be crazy.

Thanks
 

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After some search on RealOEM, that seems like the line connecting on Pressure Accumulator?
The bottom lines are also connected to the assembly for VANOS I suppose. I really hope this isn't a VANOS issue

Since relieving some pressure in the line would help from leaking, instead of replacing the VANOS, would replacing the oil separator (a.k.a. PCV?) fix the problem like 95naSTA said?
https://www.ecstuning.com/b-assembled-by-ecs-parts/oil-separator-valve-service-kit/11151406788kt2/
Parts some pretty cheap and the Labor should be between 1~1.5 hrs as I have done something similar on the S85.

Would Daily Driving the car be okay at this situation? I'm worried I will further damage the motor.
You can't relieve the pressure from those lines they are the oil feed for the vanos. If they are leaking it will just get worse, so unless you want to buy a ton of oil and oil down your engine just change the one that is leaking and its crush washers, it is an easy task. I would not drive it.
There is a thread by bdsmitty88 with identical pics as yours. He drove it the next day and the line failed completely, big mess and he had to get a tow. So get someone to help you by holding the gas down a bit 2000 rpm should work and look for your leak, it is the only way to know. You have to find where the leak is simple as that, could be anywhere, might even be low and the fan is blowing it around.
 

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You can't relieve the pressure from those lines they are the oil feed for the vanos. If they are leaking it will just get worse, so unless you want to buy a ton of oil and oil down your engine just change the one that is leaking and its crush washers, it is an easy task. I would not drive it.
There is a thread by bdsmitty88 with identical pics as yours. He drove it the next day and the line failed completely, big mess and he had to get a tow. So get someone to help you by holding the gas down a bit 2000 rpm should work and look for your leak, it is the only way to know. You have to find where the leak is simple as that, could be anywhere, might even be low and the fan is blowing it around.
Bought a bottle of CRC brake cleaner and cleaned out the oil cap seal.
Since I had to get home some how, I drove it down to my house which took about 30 minutes or so.
The oil leaking on the passenger side seems to have improved by a lot.

Sailor, the point you circled on the picture was almost completely dry. No oil.
Since the hood strut is half-burst, the hood is barely supported and the heavy wind made it impossible to inspect the car. Probably should get this thing down to a mechanic.
 

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I circled what I could see. the hoses are longer than that so could leak anywhere. There are not a lot of things that can shoot oil all over the place. If you hood shocks are shot just clamp a vise grip on the rod. It will not help the rod but you have to replace them anyway.
 

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Discussion Starter #10
* Status Update

Just changed the oil cap once again, brand spanking new.
Cleaned the area well with brake part cleaner. Totally clean.

Drove it around a couple miles, well warmed up, and ding ding ding we got an answer

Oil Cap was the culprit for shooting oil all over the place I guess. (I still don't know how the hell this is even possible?)
Brake part cleaner does a good job I guess. Even the old cap works fine now.

Although there still are some oil leak from the PCV valves connecting to plenum, most of them are fixed at this point.
PCV system replacement will be the January project
 

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* Status Update

Just changed the oil cap once again, brand spanking new.
Cleaned the area well with brake part cleaner. Totally clean.

Drove it around a couple miles, well warmed up, and ding ding ding we got an answer

Oil Cap was the culprit for shooting oil all over the place I guess. (I still don't know how the hell this is even possible?)
Brake part cleaner does a good job I guess. Even the old cap works fine now.

Although there still are some oil leak from the PCV valves connecting to plenum, most of them are fixed at this point.
PCV system replacement will be the January project
Just saying because" you don't know how it happened". It has happened before. The owner does not put the oil cap on correctly. If the old cap works and the new cap works then in all likelihood you did not have the cap on correctly when it leaked.
 

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I'm late seeing this, but I knew it was the oil cap. Happened to me in exactly the same fashion!
 

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Just saying because" you don't know how it happened". It has happened before. The owner does not put the oil cap on correctly. If the old cap works and the new cap works then in all likelihood you did not have the cap on correctly when it leaked.
I just didn't think oil can penetrate through the oil cap and reach a higher physical height i.e. plenum hehe

I'm late seeing this, but I knew it was the oil cap. Happened to me in exactly the same fashion!
Got it all cleared up now!
 
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