Working on a 2011 Countryman S with the N18 motor with one visible PCV hose coming from the left side of the engine (left when sitting in driver's seat) and going to the turbo inlet pipe. Apparently, there are passages leading from each of the intake runners to the PCV system built into the valve cover, negating the need for the right-side PCV-to-manifold connection used in the previous models (i.e. 2010 and prior that use the N14 engine). There also appear to be both a PCV diaphragm (accessible from top side of valve cover, on right, back side, and available separately), which seems to limit flow under various operating conditions, and a one-way/non-return/check valve (round, built into underside of valve cover).

The car is my mom's and she loaned it to me for a few weeks while recovering from surgery. I am doing some general repairs and tests on it to make sure it is all set for her when she is able to use it once again. A test I commonly perform on turbo cars is a boost leak test, because I am almost always able to find and repair at least a few small leaks this way. When I hooked up a pressurized air source to the compressor side of the turbo (I mounted my tester directly to the turbo after removing the turbo inlet pipe) and attempted to introduce pressurized air, however, I could not build pressure (using a 5hp/80 gallon compressor); all air seemed to be coming out of the PCV-to-turbo inlet pipe hose. Given this behavior, I have to assume that my PCV check valve has gone bad (or could it be the diaphragm?). I do not see that the check valve is separately-available or replaceable though. I imagine that running the car like this is at least making the turbo work harder to produce the same amount of boost and might even cause a low boost situation or enough pressure in the crankcase to cause oil seepage/blow seals, if bad enough. For these reasons, I'd like to resolve the issue.

The turbo appears to have a very small amount of radial play, but no axial play and is not rubbing the housing (just in case someone says that the air is pressurizing the crankcase through the turbo).

Could someone please confirm that this behavior indicates an issue and/or let me know if the check valve is replaceable without replacing the entire valve cover? Also, could the diaphragm cause this issue?

 

I can now confirm that the pressurized air coming through the front PCV port when the intake is pressurized is not normal; this was verified by checking my new valve cover for the same behavior. The new valve cover seals when positive pressure is introduced into the ports that connect, through the head, to the intake runners and a boost leak test no longer shows air coming out of the front port. When blowing into the valve cover through the bottom ports (I used my mouth and covered the other two ports with my fingers), you can hear and feel the internal check valve seat.

I have cut open the old valve cover and found the specific check valve that was causing the issue. The problematic check valve looks just like the one behind the PCV hose that connects the valve cover to the turbo inlet pipe, but it is flipped around to seal pressure inside the valve cover and not visible from the outside. I will take pictures and upload them within the next day or two so you can better see what I am referring to.

I have not yet had a chance to test drive the vehicle and see the effect on boost/performance, since I am waiting for a replacement thermostat before putting things back together, but will provide a further update in due course (boost with issue maxed out at about 4psi, should be about 10psi according to my research).

 

Still waiting for the thermostat, but attached some pictures of the old valve cover cut open, with the check valve that failed circled (the check valve you can see from the outside I broke during disassembly, was fine when on car). Also attached a picture of the diaphragm, which was torn in two places.

Also, just as an interesting aside, the car had reasonable combined fuel trims during idle and cruise, i.e. under about 7%, when I got it. I boost leak tested and also smoke tested the intake though and found the diaphragm to be leaking, so removed it for inspection and, while I was at it, cleaned quite a bit of sludge from it, before reinstalling until the new valve cover arrived (the car was only driven once for a short drive before replacing the cover). Interestingly, idle fuel trims were about 15% positive after that, with cruise trims less affected and almost as they were previously. I guess the sludge must have had a sealing effect!

Lastly, the vehicle is driven in MA and NH year round and has 105k miles on it. Oil is changed twice a year with synthetic. I provide this information for those interested in comparing their own sludge buildup to this valve cover's buildup. I have also attached a picture of the valvetrain, which is free of sludge, so I believe the engine to be healthy.

Cut open valve cover with top half flipped open partway

Valvetrain
Sludgy diaphragm

Sludge under diaphragm


Closeup of failed boost check valve

Upside-down top half of dissected valve cover showing boost check valve

Torn diaphragm

Assembled valve cover showing location of boost check valve from outside

 

This has been super informative, subscribed for the sake of my build!

 

Glad you found it helpful! Realized that I didn't take any pictures of the underside of the valve cover showing the intake manifold-to-valve cover ports. See below for those and for a few of the thermostat and crossover pipe, which I replaced at the same time and were leaking/broken into pieces, respectively!



Broken crossover Pipe (showing water-pump side)

Underside of valve cover

Leaking thermostat to crossover pipe connection

Labeled underside of valve cover showing check valve and intake runner/manifold to PCV transfer ports (earlier design used until 2011 in most coopers, but until 2013 or so in the JCW coopers)

 

I'm curious why this didn't present as a major leak and throw a CEL. Your mom must not "get on it" very often, haha.

 

I am quite curious as well... I think that you're quite right though, she drives it very carefully (slowly) and mostly in city traffic. Doesn't drive highways either, at least if it can be at all avoided. I am surprised my dad didn't trip a code though, I know that he runs it pretty hard when he drives it, usually using the excuse that my mom doesn't and that he needs to make up for that to "clean out the carbon" He hasn't driven it as much since recently getting a pickup truck to replace his van (always wanted a pickup!), so maybe that's why.

Also, just got back from a short test drive and the vehicle is now boosting as it should, spiking to 13psi or so and holding a bit less (maybe 10psi, according to MAP sensor through scantool). Hard to say exactly since I was logging using an Autel scan tool and trying to glance at the graph while driving (no recording or even max/min, or maybe I just haven't figured those features out yet!

Unfortunately, after getting home and waiting for the cooling fan to cycle (I had changed the coolant/thermostat), I noticed that the cooling fan doesn't come on for low speed operation (i.e. trigger at 105C, off at 101C, also whenever AC is on), but does come on for high speed during component testing and, presumably, when the coolant gets to 112C (I didn't let it get that hot, even 105C makes me a little nervous - most fans I have seen turn on around 95C). Ordered a new TYC unit from Amazon for $100 and will be replacing shortly.

My mom likely never noticed the slight overheating due to the lack of a temp gauge, the temp light not coming on below the high speed fan temp limit and not knowing that the fan should come on whenever the AC is on. Apparently this issue shortens AC compressor life (likely among other things), so glad I caught it early. Not terribly excited about having to remove the front bumper and crash guard just to replace a fan though!

Lastly, for the sake of being complete, I also discovered oil in my middle ECU harness connector when replacing the thermostat. This is apparently caused by a leaking oil volume control solenoid, which is located inside the oil pan. The leaky solenoid pushes oil through the cable jacket, up to the ECU. Never seen this problem before, but apparently affects a few other vehicles too.

The options to fix the ECU/oil issue, which I felt was worth fixing due to the oil eventually killing the ECU and/or migrating to and killing other sensors (e.g. O2 sensors), were to either replace the solenoid itself OR buy a repair kit that essentially plugs into the old solenoid, allowing you to push the leaking part into the oil pan, then seals the pan and provides a new connector; I went with the latter. The kit is sold through ECS Tuning (no affiliation), among others, for about $40.

Starting to regret borrowing the vehicle (mostly kidding, glad I caught this stuff before it resulted in much damage)!

 

Just wanted to say thanks, thanks(:

 

Thanks for the detailed posts and pictures! Very helpful.

 

A ton of great info here along with nice pictures. One thing to keep in mind though is you can not go by the Mini Recommended oil change cycle. You need to change the oil more frequently. It needs to be changed every 3-5 thousand miles.
Also I didn't do the conversion but the the Mini Cooper S normally runs at 220f coolant temp not sure what that works out to in celsius. I don't like it at that high of a temp but that's what it's programmed to do for emissions reasons.

 

Glad people find the information interesting and/or helpful!

Regarding oil changes, I definitely agree and have always told my parents the same. My mom only puts about 5-6k miles per year on the vehicle though (this is her second car), so oil changes are actually done at fairly reasonable intervals already, in my opinion (my dad changes the oil once in the fall and once in the spring, regardless of mileage).

Regarding coolant temp, 105c works out to 220f. 112c, when the high speed fan comes on, this car's only working mode, works out to 233.6f! I was wondering why so hot, but haven't yet had a chance to research this. Interesting that it would improve emissions/is done for emissions reasons.

 

So, pulled the radiator fan off, resistor was visibly corroded and falling apart (forgot to take picture, sorry!). Lots of plastic clips, some that are designed to be one-time use (e.g. the wheel arch trim clips), holding things together and hard to access Torx fasteners, which I find annoying since it seems like they strip if you attack them at any sort of angle at all (I stripped one holding the crash structure onto the frame horns and was able to use a carbide burr to remove the head without much issue, but lots that felt like they were on the verge of failing before coming loose). Ordered a TYC brand replacement and hope to have in on Wednesday evening, when it is scheduled to arrive. Picture of the car disassembled and ready for the replacement fan attached (the upper metal bars that hold the front end were put back with two bolts just to hold things together until the new fan arrives, upper piece is essentially loose).

Quick notes - disassembly was similar, but not identical, to the N14 mini coopers (e.g. Torx fasteners on back/bottom of crash structure in the N18). Also, I did NOT have to remove either the upper or lower coolant lines to tilt the radiator forward enough to remove the old fan and AC lines had plenty of flex as well.


Closeup

Further away

 

Quick update, car is now running as it should with no more issues, at least that I am aware of.

Regarding the radiator fan not coming on, even after replacing the fan, it still did not appear to work correctly (i.e. it did not immediately come on when AC was turned on and did not come on at 105C). I had used a commercial-style vacuum system to evacuate the cooling system, so shouldn't have had air pockets in the thermostat to worry about and was getting good heat and readings from the coolant temp sensor via the scantool following the repair. I jumped the relays and both high and low speed worked just fine, so I assumed an ECU control issue initially (I suspected my oil leak into the harness killed something in the ECU). Thankfully, this was not the case!

Apparently, the radiator fan only comes on with the AC on full when the coolant temp is above about 190F or so (it also pulls coolant temp down to about 190F when turned on, may use this to keep ECT down on hot days! - doesn't seem to happen in sport mode on this model) and there is a slight delay before the fan engages at that. I had been turning the AC on when the engine was still cold expecting the fan to engage...

Also, the cooling fan seems to come on at 107C (~225F) and my research shows that this may be due to the new thermostat operating at a slightly higher temperature. Not sure exactly how this would work with an electronically-controlled thermostat, but the fan turning on well under the high temp that would trigger the high speed fans indicates to me that the system is working as it should. Interestingly, in the 40 and 50 degree weather we've been having here, the car cannot really get hot enough to cause the fan to kick in at idle (temps stay right at 105C indefinitely without the fan kicking on --- Update - It seems like idling can't get full heat in the motor on colder days, but going for a spirited >30 minute drive then parking will get the fans to cycle at idle).

Also, the ECU harness appears to have dried up after leaking oil for a bit following the oil volume control solenoid harness extension repair (I took it off a few days in a row and sprayed out with compressed air and contact cleaner before it stopped).

 

Thank you for the detailed article. I have a very similar issue with the same engine. Last time I drove my car pretty intense in the canyons my dipstick popped out. It looked quite scary as the whole engine bay was covered in oil. But other than that the engine runs smoothly, no trouble codes, maybe a little bit of hissing sound when idling. I did also a compression test for the peace of mind and everything was fine. Do you think the same could be the problem with my PCV system?

 

Happy to contribute where I can, I know I've benefited numerous times from the write-ups of others!

Regarding the dipstick popping out, I do agree that this could be due to a faulty check valve in the valve cover/PCV system allowing boost to enter the crankcase via the valve cover, although it was not an issue on my vehicle (the boost was being allowed out the front of the valve cover by a faulty check valve, through a sealed passage in the top of the valve cover, but not into the valve cover/crankcase). The only experience I have personally had with a dipstick blowing out was on a high-mileage, tuned Audi running fairly high boost and that was due to excessive blowby (i.e. worn rings).

To confirm/better isolate your issue, it may be helpful to pressurize the intake tract. This way, you can listen for where the air is leaking without the engine running. Assuming your turbo is the same size as the one on my 2011 Mini Clubman Type S, you should be able to accomplish this using the following products to hook a source of pressurized air directly to the turbo's compressor inlet flange (after removing the turbo inlet hose - the one connecting the airbox to turbo inlet):

• Boost Leak Tester:
  Amazon
  Amazon
• Reducer Coupler Silicone Hose (1.75"(45MM) to 3.0"(76MM):
  Amazon
  Amazon

Note that you will need a reasonably-sized air compressor for this, a good locking air chuck is very helpful, and some leakage is to be expected (I believe about 1psi/second is OK, but the less leaky, the better!). This would also be a good time to check for boost leaks generally (soapy water in a spray bottle helps). It may also be helpful to rotate the crank a bit, either by bumping the starter or putting a wrench on the crank pulley, if leakage out of the intake manifold or exhaust initially seems excessive (there are locations where valve overlap can allow leakage - generally engines do not come to rest in these positions though, so not usually an issue - can't recall why exactly, but can confirm its not often an issue for me in any case).

Also, I'd suggest pressurizing up to, but not above, peak boost (about 13psi stock on the 2011 Clubman S) when checking for air leaks (when trying to determine if the valve cover is faulty, whatever pressure below peak boost that causes airflow where there shouldn't be airflow is fine).

Good luck and let us know how things work out!

 

Thank you for the hints. Unfortunately I didn't have the chance to do a proper pressure test, because of the lack of tools. However I felt quite confident about a failing PCV valve, so I took off my valve cover gasket and performed a rather simple test. I blocked two of the intake ventilation ducts with my fingers while blowing air into the third one, and as I suspected there wasn't any resistance, my intake side valve was shot. This means air can pass through the valve cover, right into the crankcase, which explains why my dipstick popped out. So I ordered a new valve cover gasket, installed it and went for a spirited 50 miles long test drive in the canyons. No problems occurred during that, actually I felt the engine a bit more responsive and stronger but maybe this is just placebo .

By the way I live in Europe where you can find these engines fitted also in Bmw 1-series, with N13 engine code. I also have to remark that my car has a tuned ecu (dynoed at 210hp) which can be the reason why the symptoms of the failing PCV valve were so dramatic. At least this way it actually turned out there was a problem with the PCV system, otherwise I wouldn't have recognized it.

 

Awesome, glad you were able to figure it out! I actually did the same test on my own valve cover once I removed it to confirm what the on-car pressure test had showed. I think that your valve cover failed in a different way to my own, but this does not surprise me, given how many check valves the valve cover includes. I also agree that the higher boost pressure I assume the motor is running in the 135i to achieve those horsepower numbers puts an added strain on the valves and likely makes any failures more severe.

In any case, thanks for sharing the outcome and information regarding the EU application of the motor, hopefully this will help the next person with a variation on this issue!

 

My pcv is dead and after some days of it death my mini lost all boost and i have no boost leaks i checked that before (pressure tested the íntercooler changed some íntercooler pipes etc) the wastegate is ok the wastegate actuator is ok i just replaced the vacuum line to the wastegate actuator so that's ok the boost controler it's ok because when the engine is off the wastegate is closed and when it's on the wastegate is opened and it wouldn't close if the boost controller was bad it would be stuck open all sensors are ok so literally i have no reason to no have any boost and the only problem is the dead pcv ¿can the dead pcv be the cause of my lost of boost? I suspected that before reading your post and after reading it i suspect more and more that the pcv made my car lost boost so can that be my problem? I ask you because you have experience with this or if anyone knows please help me :( thank you in advance .

 

From my point of view it is unlikely that a failing PCV on its own causes such boost loss. As in my case there was no boost problem, the turbocharger could easily provide sufficient boost, even when the dipstick was not in its place.

 

But what could be wrong? :(

 

Are you sure the wastegate is closed when the engine is off? On these engines, the wastegate is vacuum actuated, so when the engine is off it should be wide open…

 

Thanks for this thread!!!!.
I am having misfire problems and one of the pending things to do is to measure the crankcase pressure.
I installed the spare valve cover cap with pressure gage expecting positive pressure (N18 = 36 mBar) and only have vacuum...no positive pressure. I do not know where the vacuum comes from. The vacuum is less than 1 inHg and goes to zero when hard driving, but never positive.
Where is the vacuum coming from?.
PCV seat is not good (crack) so I am waiting for a new valve cover. Will this fix the problem?.

 

Not sure that I completely follow. Crankcase pressure might be slightly positive if you are getting significant blowby under boost, but will usually be slightly negative due to the PCV system pulling a slight vacuum on the crankcase to evacuate blowby gases. Are you sure that you are not confusing crankcase pressure with intake manifold pressure, which should see full boost (e.g. 8-13 psi or so, or almost 20psi for the JCW models)? Intake manifold pressure on these cars can be a bit weird as well; you should see strong vacuum on startup (e.g. -20 mmHg on a vacuum gauge), but that goes to near 0 after a few minutes using some sort of valve advance wizardry to reduce pumping losses, IIRC. Should still see positive pressure during hard driving though!

 

To clarify, here is my setting attached in a picture.
The spare oil cap with tube is connected to a pressure gage. Initially I installed the gage A (0 to 100 mBar) as I was expecting 36 mBar. No pressure shown as A cannot measure negative values.
I installed the gage B and showed negative pressure. About -0.5 to -1 InHg at idle.
At working temperature, gage B still shows similar negative values. When driving hard under boost, gage B shows near zero (0) pressure, but never reaches positive values.
So, my crankcase is always negative and near zero pressure.

I understand N18 valve cover engines are not connected to the intake manifold and due to VVT system, there is no negative pressure I think. I believe the throttle body creates some vacuum due to the butterfly valve at the intake, but is kind of simulated.

So I guess the whole PCV system is not good. I am expecting to change a new valve cover during the weekend to solve the issue.

 

As mentioned, if the crankcase ever goes positive, you’ve got serious problems. The PCV system is designed to keep the crankcase under vacuum. Vacuum helps with sealing the piston rings.

If you’re having misfire issues, I would replace spark plugs first, then give consideration to new coils if persistent misfires come back.