geetee

The 958.1 base Cayenne's use a VR6 motor from VW. One of the difference is the intake manifold on top of the motor. I believe the longer intake runners were placed to increase HP compared to the VW...correct me if I'm wrong on this. Anyways this makes it a little inconvenient when the PCV goes. On the VW motor, you just have to remove the valve cover and replace the whole valve cover or replace just the torn diaphragm with a an aftermarket one like RKX. On the Cayenne, you have to remove the intake and then replace the valve cover or just the diaphragm. That's the proper way to correct the issue but I tried to find a easier way to solve the issue.
Do at your own risk.
At about 105k miles, I forget what codes I had but I believe it was something related to bank 1 and/or 2 lean codes. If you open the hood, at the back of the engine there is a relieve hole at the top of the valve cover. Inside of that location is the PCV valve.


At idle, engine is noticeably loud. If you cover that hole with your finger, the noise will go away. Idle rpm was a little higher also. If you cover that hole at idle and the sound changes/stops the air leak, your PCV diaphragm is torn.
I had no other valve cover leaks so I didn't want to removed everything and replace the valve cover. I believe it would be a 3-4 hour job as I've had my 957 V8 valve cover removed at least a half dozen times for starter replacement and chasing a vacuum leak....not fun.
So, the conversion.
First, you need a few items
1. external PCV 95511076500 from amazon.$39.00. It was used on the base 3.2 03-04 cayenne. You can get a OEM one for a couple hundred if you prefer.
2. Dayco 80412 molded hose from amazon. $6.98
3. SS or coated screw. I believe it was a m4 screw about 5mm long. The screw needs to fit snug into the PCV hole to prevent air leak.
4. clamps and locktite blue.

So, first you plug that factory PCV hole with a SS or rust resistant coated screw. It was a M4? about 5mm long screw. I forget the size but is basically need to be snug/tight so that air won't leak. I used a dab of locktite blue and let it cure overnight.


next, you remove the factory hose that connects the PCV to intake manifold. It's the connector right belove the hole.



Ignore the installed external PCV picture above. That was the first one I tried and there were some issues so I redid the hose.


next picture is the external PCV with the factory connector with the 19mm ID Dayco hose.


next you are moving over/replacing the parts on the new external PCV.




You are adding 3 clamps. I didn't have any euro clamps so just used worm clamps.
You are replacing the whole bottom portion of the external PCV with the Dayco hose.
You are cutting that attachment under the PCV valve as it's not used and gets in the way.
You are also moving over your 90 degree connector from your current PCV connector that you removed from your car.
If you look at the picture above, you can see the differences.
The hose on the left is the final product before installation.

Install the new PCV pipe and you are done.



You are basically blocking the factory PCV hole/pressure relief hole and moving it downstream about 6 inches. The external PCV has it's own PCV hole so you are not altering anything .
I have just crossed 122k miles with no issues so I'm assuming everything is working.

I'm hoping this aftermarket PCV/diaphragm will last at least 60k. At that point all I have to do is replace the $39 part 95511076500 .

kari

@geetee , nice work! did you check the intake after throttle body and the insides of the new external pcv after the ~15k miles youve driven so far? Any oil or residues inside?

A torn diaphragm behaves as an failed 'open' pcv resulting as idle issues etc which is what we commonly see but adding a pcv in addition to a partially failed pcv (i.e. without removing the old diaphragm and clearing airways of the old pcv inside the valve cover) could potentially create a scenario of a stuck 'closed' or 'partially closed' pcv system that could affect oil consumption as well as damage the seals in the long run?

My pcv seems to be in the early stages of failure ( no codes but hear a faint hum that quietens when i close the hole with my finger). Not sure if that indicates imminent failure or not but debsting to either do a preventative full replacement of pcv diaphragm and valve gaskets or do the external conversion atleast for the short term till i have everything ready for the internal pcv change..

geetee

I have not checked the intake after TB.
The new PCV hose has oil in it just like the stock hose did. I guess you could install a catch can there to prevent oil dumping back into the intake manifold.
My rationale was that due to the diaphragm being torn/"open", the spring that normally push/pull the diaphragm wasn't functioning anyways. By blocking that hole with a screw, I would be bypassing the factory PCV and the newly installed PCV would be taking over the same duties instead.

ChrisChong948

Have a 958.1 base with the same PCV issue. I believe mine is in the early stages as well, it makes an “oscillation sound” at idle, sometimes changing with RPM found an identical sounding vid on here, later said to be PCV issue. Of course I would prefer to fix it myself the “correct way” but since it requires so much extra work maybe this is worth a shot. Car definitely needs spark plugs, coils, maybe some other things.

Contemplating trading it for something else because of all these things but I really don’t know what I would replace it with. Already have a CTT in the stable alongside the base so I don’t need two cayennes but certainly have loved the base for its bulletproof reliability up until this point.

kari

I finally got to changing the diaphragm.. in my case i could not see any tear in the diaphragm.. only had the sound . I had to hold the diaphragm under a flashlight to see points of wear where it had worn thin.. so there could be microscopic holes but i felt that the diaphragm had stretched making it ineffective vs getting actually torn. So if going the way of an external pcv i feel removing the inner diaphragm or atleast using a pick or fine tool to actually tear the old diaphragm is a good option when installing an extenal pcv ..

bartekgombos

Thanks for the detailed description of the external PCV valve fix. I ordered the parts and had them installed in my 2008 Cayenne V6. It fixed the problem with unstable idle and the engine was running great. After few weeks, when the weather got warmer - I had a situation when accelerated on the highway and when engine reached ~6000 RPM it suddenly lost all power like if the fuel was cut off. The car abruptly decelerated and once the RPM got lower to ~4000 it came back with full power. I was able to get home but on the way when I stopped on red light, the idle was fluctuating. At home I opened the hood and found that the thick walled PCV valve pipe (Dayco 80412) was completely flat - collapsed from the vacuum. It later got back to its original round shape and the engine runs fine, but whenever I run to ~5000 RPM the engine cuts off which can be dangerous if someone if following too closely.
I think the Dayco 80412 coolant hose is not strong enough to hold against the vacuum at higher RPM (especially when it gets hot). I'll try to stiffen it by putting a piece of metal pipe inside (if I can find a right size) or find a better vacuum hose to replace it.
In the meantime I use the car daily to drive to work - just have to be gentle on the throttle an not to run over 4000 RPM.

bartekgombos

Update: I installed a piece of 18mm OD metal pipe (galvanized electrical conduit 1/2" size) inside the hose to stop it from collapsing and the car drives perfectly! No issues with high RPM.

mdistel

Appreciate the update and willingness to test this alternative solution for a very bad design. If the PCV fails again in either of my base cayennes I'll try this option.

Mark

Gio_Hb

can you attach an image please?

Gio_Hb

Hoping to try this on mine, but i am getting a squeak sound in addition to the “leak” sound. Not sure if its a bad PCV or a pulley before diving into that.

Video post

mdistel

PCV sounds bad. I've got original pulleys on my 2009 and they are quiet, PCV died at 135k. 2016 had bad PCV at 65k. With the engine dead cold remove the belt and run it to confirm there is no pulley noise. On my BMWs I pulled the pullies and regreased them frequently, they fail often.

Mark
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Gio_Hb

Does a dead PCV cause that "squeak" noise or just the vacuum leak ? I'm kinda lost between the two noises. Not sure where to start. I checked on the pulleys while changing the tensioner, no grinding or metal sounds from any of them. I guess it's happening on high RPM ?

Also, performing the "external conversion" done here, does it eliminate the noise? (I checked the air filter, no oil or leaks)

mdistel

Both of mine made different noises that could be traced to the back of the engine but it was tough to pinpoint. Covering the hole and having it go away was key to diagnosing. My 2009 was throwing codes, the 2016 I only heard so possibly caught it early.

​​​I did the aftermarket PCV repair rkxtexh.com on my 2009. 2016 was covered by CPO so new valve cover. The external fix should stop the noise as that is basically a whistle or harmonic sound due to air pass through that shouldn't.

Mark

mdistel

The other thing to consider is if you have a valve cover gasket leak, mine was just starting to deep at the back of the engine but it was like plastic when I pulled it out. Advantof the external fix is it's far easier and less expensive. I broke 2 vacuum hoses as they are brittle plastic. Dealership broke one on the 2016. I was literally kneeling on the intake manifold to get the fuel lines reconnected so it's not really a fun job.

Mark

geetee

Quick update....I've put 30k+ miles so far on the external PCV....only change i've made is that a catch can was added 9-10k? miles ago.

I see that someone posted above that the dayco hose collapsing. It's been averaging 90 degrees where I'm at and I've redlined 1-3rd gears without any issues. I've repeated this many times over the past month without any issue. I wonder if this is a 957 issues? as the person posted has a 08. My 2012/958.1 does not have this issue.