[kis2012]

2007 80k miles N53 325i conv

I think the PCV is stuck or faulty on my car. It is built into the valve cover, I presume it is the same as the N52 but the test procedure I see online does differ slightly.

Almost all the examples of a bad PCV I find online, are leaking from the breather hole on the PCV, or making a whistling noise.
Mine is not doing this. What I do have, is excessive suction from the oil filler cap.

Car runs perfectly when warm. When cold it can stumble a little at idle and sometimes the revs rise and fall a bit (100-300rpm maybe). I have been trying to track this issue down, suspecting it is the injectors, which it still may be. They are all index 11 and less than 35k miles old.
I have Nox sensor codes but stratified charge mode is ok. Issues were present before the Nox codes I think.

I decided to check the PCV as per the Bimmerprofs website.
Test 1 - cover the hole - does nothing. Makes no difference.
Test 2 - watch the fuel trims (integrators) while removing the oil cap.
This results in the engine nearly stalling, the revs dropped considerably, the fuel trims rise to +30% (which I believe is maxed out) all within 2 seconds or so. This, according to that one and only reference I can see, means the PCV is bad. I also got a half engine light on from this test. Which was the HPFP saying the fuel pressure was too high, it cleared after and did not return.

Can anyone confirm the PCV is likely bad?
Can anyone point to a thread on replacing just the valve, rather than the whole valve cover?
Can anyone recommend an aftermarket PCV? Autodoc seem to sell them.
(I'd rather try and fix the PCV than replace the whole cover at this time because of the Nox sensor costs and maybe more).
Thanks

[sonofsun]

Remove the 1/4" hose coming off the intake providing vacuum to the cyclone separator. Then check suction at the oil cap before and after doing this.

[kis2012]

Originally Posted by sonofsun

Remove the 1/4" hose coming off the intake providing vacuum to the cyclone separator. Then check suction at the oil cap before and after doing this.

Many thanks for your post.

I located the pipe in question.
I tested the car again, engine had idled for 5 minutes or so.
Opened the oil cap and the integrators, short term trims shot up to max and the engine almost stalls.
Turned car off. Disconnected the pipe from the back of the engine cover and blocked both sides, just to be sure.
Started car again and removed oil cap, this time the car was fine and the trims stayed roughly the same.

I think conclusive proof that the PCV is faulty.

Ordered an aftermarket replacement PCV membrane and cap.

Fitted the above and used high temp silicone sealant to seal the cap.

Tested car again and it is just as bad.
What did I do wrong, the cap seems like it is sealed ok and the old membrane that came out, the factory original one, was fine. I cleaned up inside the cap as best as possible, I reused the factory spring after cleaning it.

How can it be that it is exactly the same as before?

[IMG][/IMG]

[jesspl]

Having issues with what I think is my pcv valve also. 2010 e90 323i, rough idle and jerking, and this noise... following this post incase it's useful for me

Good luck with your car!

engine bay noise

[lookalikehuuh]

Originally Posted by jesspl

Having issues with what I think is my pcv valve also. 2010 e90 323i, rough idle and jerking, and this noise... following this post incase it's useful for me

Good luck with your car!

engine bay noise

Yes, that's the classic sound of the PCV membrane being ripped. It causes air to come in thru the rear main seal, that's the squealing noise that you are hearing.

[sonofsun]

Not sure too much about your model valve cover. The PCV cyclone oil mist separator is integral to the valve cover on my N51 engine and needs that 1/4" vacuum connection to the intake for it to function. The whole assembly is sonic welded at factory.

I've seen ebay kits to replace just the PCV. Not sure if it can be done insitu. One needs to make a clean surface cut with no jagged edges and make sure the new valve fits without any gaps, apply some sealant , hold it tight and then check it.

[mattanderson]

Any luck, OP?

Have you replaced the PCV hose on the back of the engine?

[kis2012]

I don't suspect any issue with the PCV hose, the engine ran fine at idle with the PCV hose and valve cover end blocked off, so I suspect that the PCV in the valve cover is still the issue here, despite changing it.

This is my understanding of the N53 PCV.

At idle, in homogenous mode with a warm engine, the PCV should be closed. There should not be any air coming out of the vent hole on top of the PCV and covering this hole should not make any difference, as the purpose of this hole, is only to vent the air, as the membrane moves up and down.

If the PCV does not close, as in my case, you get excessive suction from the oil filler cap and opening it causes the engine to stumble and the fuel trims to go up rapidly.

If the PCV membrane is damaged, it will not seal up and effectively close the PCV, it may suck air in via the vent hole or make a whistling sound as air is drawn in elsewhere past a seal.

Blocking the PCV hose on the back of the engine effectively closes the valve manually and this should reduce the vacuum at the oil filler cap, when you open it as the engine runs, it will not almost stall and cause the trims to max out as before.

To that end, I have ordered a new Febi valve cover and will swap it out this week. Hopefully, I had a stuck PCV that for some reason, is still stuck after replacing it and cleaning inside where it sits.

[mattanderson]

Thanks for the update and explanation.

Keep us posted!

I suspect I'll be heading down a similar path soon.

[kis2012]

I'm struggling with this car at the moment. It's really trying my patience.

I have replaced the valve cover with a Febi part.

Nothing has changed.

If I start the car and let it idle for 5 minutes, then open the oil fill cap, the engine almost stalls, there is, what I think is, excessive suction on removing the oil cap. The only measurable value I have for this, is from bimmerprofs and he says; if the fuel trims max out when you open the oil fill cap, the PCV is open and at idle, it shouldn't be. So you have a bad PCV.

However, three PCV valves have done the same thing, and even the original BMW valve looked fine when removed.

If I drive the car around the block and repeat the test, removing the oil cap has no noticeable suction and the car doesn't immediately react when opening the oil fill cap. So the valve is closed.

https://bimmerprofs.com/crankcase-ventilation/

Is Bimmerprofs wrong, or am I missing something?
Could a leaking valve cover breather hose cause this?
If the hose leaks when cold, this might reduce the suction and cause the valve not to close. But the whole issue is excessive suction in the valve cover. Not a lack of suction. I'm lost.

[lucason91]

You are not alone on this one

You have probably sorted this out by now since it is been like three months since your last post, but I will share this anyway in case it helps someone else.

Recently, as preventive maintenance, I changed my OEM N53 valve cover because the valve cover gasket was leaking oil onto the spark plugs, and sometimes the PCV would make Chewbacca noises when warm. Other than that, the engine ran perfectly, both cold and warm.

I ordered a Febi 176165 valve cover as a replacement for under €200. I replaced it using a new BMW OEM valve cover gasket just to be extra safe against oil leaks. And guess what - exactly the same scenario as yours: very strong suction at the oil filler cap. The PCV is not closing and is stuck open.

This is definitely a faulty part. I contacted customer support at the shop where I ordered the valve cover (Autodoc), and they refunded my money within 3 days without requesting any photos or videos. Short message about a bad PCV was sufficient for them, which makes me think this isn’t the first time a refund has been requested for Febi valve covers.
Later, while trying to diagnose it more deeply, I found that by applying a bit of air pressure into the PCV vent hole, the membrane closes and the engine idles normally. It seems to me that Febi and probably other aftermarket manufacturers are using harder springs than the OEM spec.

I am going to try cutting out the PCV from the Febi cover and replacing the spring with one from the OEM unit. I have ordered extra membranes and plastic covers from different shops for €5–9. I will update if I succeed.