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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > DIY Guides > N55 - Replacing PCV w/out replacing Valve Cover



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      05-15-2017, 08:29 PM   #1
AJ9x
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N55 - Replacing PCV w/out replacing Valve Cover

My engine developed a high pitch whining noise (sounds like it is coming from under the engine). At first, thought it was a squeaky belt. Sprayed some water on it, nope. A telltale sign is removing your oil cap at idle. Noise goes away with a sensible vacuum pull on the oil cap. If this sounds like you, probably a bad PCV (in particular, the rubber diaphragm).

Local BMW shop (non-stealership) quoted me at around $1500 to replace the entire valve cover as the PCV valve is built into the valve cover.

I dug around and found a very informative thread (http://www.e90post.com/forums/showthread.php?t=1197666). I went to a website (https://vanos-bmw.com/membrane-for-b...er-11127570292) that sold a PCV repair kit for about $40 which involves a little patch job. They have a $20 option to replace just the diaphragm, but from experience, the $40 replacement part is the way to go. Much easier when installing it. Obviously as the PCV is built into the valve cover, you'll need to cut the old one out. Yes, I said cut, but don't be alarmed! It's actually fairly easy. I did this in about 30 min.

Things I needed:
1) Nut driver (hose clamps to remove air intake)
2) Small hand saw (pilot cut on PCV)
3) Oscillating saw (cut out PCV)
4) Small broomstick (to hold down new PCV against spring pressure)
5) JB Weld

First thing I did was remove the engine covers and pulled the air intake out of the way. I more or less modified my engine cover for ease of access, but you certainly don't have to. The PCV valve should be completely exposed. It is on the top of the engine about mid way back, looks like a big cap with a little 90 degree air port on the top. It sits in between the Y shaped fuel rail tubing.

The next thing you'll want to do is measure how much of the PCV valve to cut based on how tall the replacement PCV part is so it'll be about the same height when it's finished. To make the cut, I used a small hand saw to cut a pilot groove all the way around, then used an oscillating saw to make the full cut. (pics attached)

With the PCV valve now open, you can discard the old top of the PCV, but KEEP THE SPRING! When I removed mine, I saw my PCV diaphragm had some tears in it indicating failure. With the PCV area open, there's probably a little gunk build up inside and on the spring. Clean it all up with some rags and solution (pics attached). Make sure you are thorough since you did just cut plastic into the PCV area. I also used some paper towels to cover the small opening into the engine after cleaning it out. Replace the spring back inside properly (pics attached). Next, place the new replacement part on top of the spring with the spring lined up (pics attached). There are some alignment guides that will ensure the new part is on properly, you will feel this. Spring pressure will want to push up on the replacement part once you have it on and aligned, but I used a small broom stick to place on top of the PCV and wedged it in a spot on the underside of my hood. This helped keep the top of the PCV in place against spring pressure while I sealed it together. (pics attached)



To seal this together, I suggest using JB Weld over Plastic Epoxy because it has a longer working time. I used about a quarter size of the black stuff and a quarter size of the white stuff. I used a small paint brush to apply the JB Weld all the way around. IMPORTANT - DO NOT PUSH THE JB WELD INTO THE INSIDE OF THE PCV. Doing so will obstruct the internals of the PCV valve and you're back to the same problem you started with. Once the JB Weld is on, use a scraper to even it out (pics attached). Make sure there are no holes/gaps in the JB Weld after applying it (pics attached). Once the JB Weld is on, let it dry (15-24hrs).

After the JB Weld dries, replace everything you took out (air intake, engine covers) and you should be good to go. One more note, do not use a clamp or anything that will compress the sides of the PCV as it is very sensitive to external pressure. This can cause interference with the internal operation of the PCV and the noise will come back. Sounds weird, I know, but this is experience talking.

Seems like a weird patch job, but it did the trick. No more high pitched whining noises. And while it might be best to remove the entire valve cover to do this, if you're going to go through that trouble, might as well replace the valve cover itself.

Hope it helped!

http://i3.photobucket.com/albums/y87...514_122643.jpg
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Last edited by AJ9x; 05-16-2017 at 12:29 AM.
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      05-15-2017, 11:39 PM   #2
vespa
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Wow! Nice work! How hard was it to get all the plastic chips out after cutting? Do you have any pics of the failed diaphragm? Any idea what might have caused it to fail?
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      05-16-2017, 12:26 AM   #3
AJ9x
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Quote:
Originally Posted by vespa View Post
Wow! Nice work! How hard was it to get all the plastic chips out after cutting? Do you have any pics of the failed diaphragm? Any idea what might have caused it to fail?
Not bad, most of the saw dust fell outside of the engine. The little bit that fell inside was easy to clean up and the crankcase port was easy to clean out.

Here's a pic of the failed diaphragm. Doesn't look like much, but when you're talking vacuum, it doesn't take much.

http://i3.photobucket.com/albums/y87...217_161504.jpg

My guess on what caused it to fail (other than age @55k miles) is running higher boost on an E85 mix/JB4. The noise changed very noticeably depending on my boost setting. The specific mechanics on it, I'm not exactly sure. Just know that with more boost came more crankcase vacuum and more noise.
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