I've had my 2017 Cooper S for about 18 months, and courtesy of some electrical issues (ahem) and a dead motor mount (ahem) I've gotten to the point where I've disassembled parts of the engine and put them back together again... a couple of times.

I have always maintained my own vehicles to the extent I am capable, so this has been a "get to know this car" exercise, and a good one. Every time I am under the hood or the like, I'm paying attention to what is going on, looking for any abnormals, and looking for anything that has changed since the last time.

While doing all this takeapart/put-together I ran into 3 things and would love some informed guidance on what they might mean. Bear in mind that I am the second owner of the car, so things I'm seeing may be the result of first-owner maintenance regimen rather than something I'm doing.

1. The intake port gaskets for cylinders 1 and 2 had clearly been blown. There was dirty engine oil on the cylinder head between the two gaskets as well as below them (but clean above them both, clean to the left of cylinder 2, and clean to the right of cylinder 1). Without removing the intake manifold you can't view where all that oil would have dripped into to even know there was trouble there; but upon removal, I could see where all that blow-by oil had been dripping to, and it had definitely been dripping there for a while.
   
2. The oil fill cap gasket was also blown (or at least getting blown by, maybe it's by design, I don't know). With the engine cover removed I had cleaned around the cap more than once, and realized that I was doing mop-up for an ongoing issue rather than simple past dirtiness. There is a light sheen of oil that keeps returning on the raised edge of the cylinder head cover behind the cap, and on another raised edge just under 1" in front of the cap. Cleaned it about 2 days ago, and just looked and it's back again.
   
3. A light sheen of oil on the bottom of the oil pan. I believe I have traced this to the oil filter drain plug but I won't know for sure until I do another oil change (should be doing that next week). It is entirely possible that I didn't quite clean the lower housing properly at the last oil change -- that's my guess -- but figured I'd mention it since I'm talking about oil finding its way out of the engine.

I'm replacing the oil fill cap today. That's a no-brainer. And when I change the oil next week, I'm going to be particular about that lower filter housing and the filter drain plug (I replace the filter drain plug every time -- I have done the last 2 oil changes and this will be my 3rd). I'll also be replacing the intake port gaskets in a few days, when I have the intake off the car for hopefully the last time to do some other work.

My question, though, especially thinking about the oil cap and the blown intake port gaskets at cylinders 1 and 2, is whether I should be concerned about this being a symptom of overpressure within the engine -- and whether that is a past issue or a present one.

• With both oil changes I've done I have put exactly 5 liters of oil in the engine. Spec is actually 5.25 liters for the B46, so if anything, I have definitely avoided overfilling, and overfilling is what would cause overpressure. Underfilling by .25 L should not.
• Taking overfilling under my ownership off the table, I suspect overfilling under the prior owner, and that the gasket failures have been present since before I bought the car (just unknown to me until now).
• With issues originating under the prior owner on the table, I'm wondering about what would be the PCV system on a different car -- but I can't figure out where the PCV valve or equivalent is on this B46 engine to even check its condition (or that of things connected to it). Any intel on this?

So, looking to gather thoughts here. I try to take very good proactive care of my engines, and gasket-blowings are a sign that at least in the past this one needed a little attention. Trying to understand what the signs are telling me so I can be thorough, rather than superficial, in this mop-up/detective work exercise.

EDIT: I changed out the oil filler cap this morning. Still getting blow-by through its gasket onto the cylinder head cover, so I apparently have a thing going on currently.

Thanks!

 

It sounds like you are getting excess crankcase pressure buildup, which is venting by pushing oil out where ever it can...this is not good. Only two ways you can get crankcase pressure like that, 1) Piston ring blow-by and 2) PCV system malfunction. The ring blow-by is a lower possible cause, but can be check with a cylinder leak-down check (not compression check, but a leak-down test). I believe you are on the right path with the PCV system and would certainly dig into things to see what isn't working properly.

I honestly don't know how the PCV system is on our MINI's, as I haven't had to deal with any issues at this point, but I do know they need some sort of one-way check valve to prevent positive intake pressure turning into positive crankcase pressure while under boost. If you can't find a schematic of the PCV system, you should be able to trace the PCV lines around the engine, since it sounds like you know your way around a valve cover. Wish I could help more and interested what you come up with.

 

Your take on this is the same as mine. Excess crankcase pressure buildup, venting by pushing oil out as such a situation does.

I had not thought about piston ring blow-by -- that would be un-fun to take on. I'm going to put my $5 on a PCV system issue as well, though there (based on nosing around BMW forums) may be some things tied to the turbo in general on these engines (still working out which BMW vehicles have the B46, and whether reports based on the B48 apply).

I have actually been banging my head trying to figure out whether this engine has a PCV valve, which would be the first thing to check -- and if so, where on earth it is. I can't even find solid references to a PCV valve in the B46. If you have any idea how to identify the PCV lines around the engine -- I am not fully sure how to ID those, and distinguish from *fuel* vapor-carrying lines which I *have* identified -- I'd appreciate them. I do have a technical document on the Bx6 engines from BMW, not a service manual but a pretty long how-this-thing-works, and I'm kind of getting the sense that all this might be within the valve cover itself? Not sure.

 

https://www.newtis.info/tisv2/a/en/f...ase/1VncaSqFda

 

en | jstancampiano
newTISHome / MINI F56 Cooper S Hatchback / Wiring Diagrams and Functional Description / Power train / Engine electronics / Crankcase /

From new TIS
Crankcase ventilation

Blow-by gases developing during combustion (combustion gas rate reaching the crankcase without having passed through the piston) must not be emitted into the atmosphere as part of an uncontrolled process. For this reason, crankcase ventilation is firstly tasked with re-supplying the gases to combustion and secondly, to generate a controlled vacuum in the crankcase.

Oil contained in blow-by gases must also be separated using an oil separator.

System functions

Schematic crankcase ventilation overview

As a rule, there are two crankcase ventilation operating modes:

Crankcase ventilation in partial load operation:

In partial load operation there is a vacuum in the intake system. As a result of this vacuum blow-by gases are drawn off from the crankcase through the oil separator using the crankcase vent valve. Oil content in gases is separated in the oil separator. The volumetric flow via the crank case vent valve is higher than the volumetric flow of the generated blow-by gases. The crankcase has been sealed from ambient pressure. This results in a vacuum in the crankcase and its adjacent lines. The system is supplied with fresh air using a bypass (integrated into the non-return valve on the clean air pipe). This proportion of fresh air is used to restrict the minimum occurring vacuum in the crankcase.


Item Explanation Item Explanation B Ambient pressure C Partial vacuum D Exhaust gas E Engine oil F Blow-by gas

1 Air filter 2 Intake plenum 3 Perforated panels 4 Channel in cylinder head and cylinder head cover 5 Oil return 6 Purge air line 7 Non-return valve 8 Crankcase 9 Oil sump 10 Oil return 11 Exhaust turbocharger 12 Oil return non-return valve 13 Charge air intake pipe 14 Channel to charge air intake pipe 15 Non-return valve with throttle 16 Throttle valve 17 Pressure control valve 18 Non-return valve with throttle

Crankcase ventilation in full load operation or with turbocharging:

In full load operation the intake system does not establish a vacuum, but in some cases, there is even excess pressure in the system and consequently, direct crankcase ventilation of the blow-by gases in the intake system is not possible. As a result of the pressure ratio at the crankcase vent valve it closes the connection between oil separator and intake system. Consequently the blow-by gas is pressed through the oil separator. The blow-by gas is routed to the connection upstream of the exhaust turbocharger via the ventilation line. The non-return valve installed at this point opens. The blow-by gas is supplied to the engine together with the fresh air that is drawn in. In this state the pressure in the crankcase approximately equates to ambient pressure.


Item Explanation Item Explanation A Charging pressure C Partial vacuum D Exhaust gas E Engine oil F Blow-by gas

1 Air filter 2 Intake plenum 3 Perforated panels 4 Channel in cylinder head and cylinder head cover 5 Oil return 6 Purge air line 7 Non-return valve 8 Crankcase 9 Oil sump 10 Oil return 11 Exhaust turbocharger 12 Oil return non-return valve 13 Charge air intake pipe 14 Channel to charge air intake pipe 15 Non-return valve with throttle 16 Throttle valve 17 Pressure control valve 18 Non-return valve with throttleMaby this can help,

Joe
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Thx @TVPostSound , @Jstancampiano , figures what would be available would be a Van Gogh when what you really need is a photograph

Guess the next step is physical engine dissection

 

Well, back again, I got rid of my failed oil filter housing and its associated coolant leak, and I additionally replaced the gaskets on the intake manifold.

As part of all that I also cleaned up the area around my oil filler cap -- got rid of all blow-by residue on the valve cover head. Not that there was a lot, but as noted there was definitely vapor coming out of there.

Post-replacement of the oil filter housing and after 1st test drive, I still ended up with blow-by residue on the valve cover head near the oil filler cap. I'm positive at this point I have some sort of crankcase ventilation issue. After doing some reading -- I found a humongous PDF on the B46 engine over in a BMW forum -- I know that most of the guts of the crankcase ventilation system are embedded in the cylinder head cover. But there are a couple of crankcase ventilation hoses attached to the clean air pipe that runs across the rear of the engine bay, so when I can I'm going to try to get at them to confirm/deny that (1) all fittings are secure and (2) all hoses are in good condition.

 

Hope this helps!

From Dutch Mini Dealer parts catalog online.

Part numbers are international.

 

Thanks. Found this writeup, which confirms (among other things) that outside of those 2 hoses, there is a lot of mystery here diagnostically, because the rest is embedded within the cylinder head:

https://bimmerprofs.com/ccv-turbo-engines/

 

Waving a magic wand over this thread to de-necro it.

So I'm circling back to this again because I have learned a bit more, understand a bit more -- and trying to sort possibilities and next steps.

2 things have landed in my lap that make this more interesting.

1. At the 2:48 minute:second mark in the YouTube video at the end of this post, someone is tearing down what appears to me to be a B48 engine (vs a B46, but may as well be same for this discussion) that has exactly the symptom I'm encountering, and makes note of that symptom visually and with commentary before moving on (his encounter of it is incidental to the video's mission). It's worth a quick look and listen.

2. In a discussion I was having in another Mini space, someone in France noted having this symptom and -- if the translation of the French isn't mangled (and it is at least partially mangled, hence the uncertainty) -- the issue came down to replacing part #1 in the post by @Speedy-218 upthread. The implication, I suppose, could be that that pipe is partially clogged.

Regarding that pipe, the diagrams still further upthread (and also in TIS and BMW's B46 Engine Technical Training PDF) show that pipe's airflow as valve cover --> intake charge pipe, courtesy of a non-return valve in the valve cover. I can see that valve if I pop the hose, examined its condition and mobility, and it pretty much works like a traditional PCV valve, super-cheap plastic version. It's basically a tiny plastic piston, no springs holding it in place, shaped like a flat rather than domed plunger. When the engine is not running it is closed. It takes air flowing from valve cover --> intake charge pipe to move the piston, and it moves vertically.

In my case the piston moved freely. There was oil from blowby gases but this being a crankcase ventilation channel, that's normal. There was not a lot of oil, just enough to see and smell and say "yep, stuff here, not dry." I took some Berryman's B-12 to it just for the heck of it and it did not make the piston movement any more or less free.

If that particular pipe is at issue, I expect to find it gummed up with stuff -- which is normal for PCV hoses on engines after a certain amount of age/wear/use -- not 100% clogged, but definitely enough to qualify as "caked" and inner-diameter-reducing. But I have to pull the charge pipe of the back of the engine to get to its other end. I'll do that, just not doing it today.

Anyway, if this provides additional insight, bright ideas, or prompts someone to tell their own tale of experience with this system, I'm interested.

Also, I clearly understand now that there are multiple non-return crankcase ventilation valves in the valve cover, as well as one in the other tube (part #2 in the parts diagram upthread). I'm wondering if it's worth, with respect to the valve cover head, getting the right kind of cleaner up in there to try to do its thing. Strengthwise, Berryman's B-12 would be first choice, but something foaming rather than strictly spraying liquid might be needed to get in whatever nooks and crannies. And for the non-return valve buried within part #2, while cleaning might be possible, part replacement is probably best guess.

Very interested in any and all thoughts. Hey @cmt52663 , curious as to what you might make of this in the context of the B46/B48 high-mileage discussions?

Aforementioned link below. Again, point of interest is the 2:48 mark. I have the exact same thing going on, and post-cleaning it returns during a single drive.