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7 Series - E38 (1995 - 2001)

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  #1  
Old 04-22-2011, 01:25 AM
Corey's Auto Corey's Auto is offline
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CCV valve and vaccum leak diagnotics

This is my first post, I just wanted to clarify the operation of the ccv valve (this applies to the 5 and 3 series as well.) I've read many posts in the past on how to tell if yours is bad and how to replace, but I thought I might share a little info that will help with vacuum leak diagnostics when the ccv is in fact good. I see the problem quite frequently in my shop.

The ccv valve used in bmw engines works very differently than almost any other design. Most ventilation valves allow a predetermined flow of fresh air through the engine crankcase to prevent acidic vapor buildup from blowby. The amount of air is often dependent on intake manifold vacuum. The ccv on the other hand is designed to ONLY open when there is an ABSENCE of vacuum in the crankcase. The diaphram in the ccv will be fully open upon startup for a brief second until engine vacuum accumulates in the crankcase, at which point the valve will then close. If your crankcase is not completely sealed with a perfect airtight seal at all gaskets, the ccv WILL open and create a vacuum leak. BMW engineers designed the valve to only open to permit blowby to be sucked into the manifold, there is no fresh air/breather intake into the crankcase.

What all this means is that if you have a rough running engine and a known good ccv valve and maf, the first thing you should do is check the short and long term fuel trims. You can use almost any scan tool with live data for this. The combined long and short term fuel trims for our cars should end up somewhere between -3 and +3. Often I will see 02 sensor out of range codes and maf sensor codes on an engine with a rough idle. If you check you will often find a long term fuel trim of 0 (due to the 02 sensors being out of range), and a short term fuel trim of 25 or close to it. 25 indicates the dme is trying to add fuel to a very lean mixture. At 25, the dme is already at its limits as far as trim goes. This often indicates leaking valve cover gaskets creating a vacuum leak which allows the ccv to open when it otherwise shouldn't.

Also don't forget that you can also have leaky gaskets on the intake side that will cause high fuel trim values. A great way to track them down if you see the fuel trim way off is to spray all around the intake manifold and valve covers with starting fluid while the engine is running and listen for changes in the rpm and how the engine runs. A large leak or crushed valve cover gasket will become very apparent. I have even seen new valve cover gaskets that were installed improperly by crushing or twisting the gasket without realizing it. These might even run fine for a while until the leak grows and gets big enough that the dme can no longer compensate for it.

Also, after you replace the failing gasket, make sure you unplug your battery for 10 minutes to reset the long term fuel trims, otherwise it will most likely still run pretty rough and be way too rich. Or if you have carsoft or a gt1, just reset the fuel adaptation values.

Please forgive me if any of this information has already been mentioned by others before. I just wanted to write an article and share my experience. Thanks
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  #2  
Old 04-22-2011, 06:44 AM
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joyism5 joyism5 is offline
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Quote:
Originally Posted by Corey's Auto View Post
This is my first post, I just wanted to clarify the operation of the ccv valve
The amount of air is often dependent on intake manifold vacuum. The ccv on the other hand is designed to ONLY open when there is an ABSENCE of vacuum in the crankcase. The diaphram in the ccv will be fully open upon startup for a brief second until engine vacuum accumulates in the crankcase, at which point the valve will then close.
Nice post Corey. Not to disagree , I do have a question :

Are you trying to say that Is designed to be always open and close when the flow is big through it? If yes , sorry for question. If not, I'm all ears...
If you take the positive crankcase ventilation valve and suck air through the hole where the intake pipe is connecting you will see that you can always suck the air. But if you change the speed of the air absorbed the diaphragm will close . This makes me believe that air is going through the diaphragm at all the times and it is open but is closing when the pressure on it is greater. For instance is open when the engine is idling or the rpm increase until a certain point and under a sudden acceleration is closing. So with another words it does not allow more air than needed to be absorbed by the intake vacuum.

I might got this wrong , and if I did please make some light on it.

This is a Quote from alldata :
Purpose :
The Positive Crankcase Ventilation Valve (PCV) system directs crankcase "blowby" to the intake system in order to prevent vapors from escaping to the atmosphere.
How it runs:
The blow-by gasses which are produced during engine operation collect in the crankcase.

The crankcase is ventilated by a pressure controlled system. The oil vapors in the crankcase enter a cyclone-type liquid/vapor separator (OSV-behind the timing chain) which allows the liquid oil to return to the oil pan and the oil vapors to be drawn into the intake manifold via a pressure control valve.

The pressure control valve is centrally located in the rear end cover of the intake manifold and is connected directly to the cyclone-type separator via aluminum pipe. It varies the pressure in the crankcase continuously depending on engine load and speed conditions. This prevents blue exhaust smoke and excessive oil consumption on deceleration due to peaking manifold vacuum, and assures reliable crankcase venting during all other engine operating conditions
.


So knowing this, is the PCV always open and close under big pressure conditions?


UPDATE: This is a must read for those looking for more information : http://www.bimmerfest.com/forums/sho...d.php?t=534005

Last edited by joyism5; 04-29-2011 at 10:16 AM. Reason: updated link
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  #3  
Old 04-23-2011, 06:22 PM
Corey's Auto Corey's Auto is offline
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[QUOTE=joyism5;6014347]Nice post Corey. Not to disagree , I do have a question :

Are you trying to say that Is designed to be always open and close when the flow is big through it?

---

The opposite actually. The crankcase is sealed. There is no vent to the crankcase for air to enter either metered by the maf or unmetered. The only way air can enter the crankcase is due to blowby or a leaking seal/gasket. If you take your ccv off you can apply vaccum to the manifold port and hold your finger over the port to the crankcase (simulating a good sealed crankcase.) The diaphram will instantly close. Then release your finger from the crankcase port even the slightest bit and the diaphram will open. Very simple actually. No need to worry about metering air or what not. The only thing that should ever cause the ccv to open is blowby gasses, and it does not matter how much the ccv does or doesn't open, because there should be no air for the ccv to suck through besides for the blowby. (This is why perfectly sealed gaskets are so important.)

PS - I have alldata too and did notice the description from them about the pcv. This is generally how a pcv system does work, however not for bmw, which is why i felt i needed to make a post about this as i see a lot of people thinking about it the wrong way. I have been able to solve a ton of driveability issues diagnosing using this philosophy. Many times the customer had been to several other shops and spent hundreds of dollars trying to fix a rough idle or driveability problem with the problem never getting fixed because the others thought the bmw pcv system worked the way it is described in alldata. It does not. Other manufactures do not use the type of system bmw uses because it means one small leak from a valve cover gasket can make a lean mixture. And valve cover gaskets are probably the most common gasket to leak on any brand of vehicle.

Any other questions please ask. Also, I don't know if it is allowed in the forum rules or not, but if anyone needs anything in particular from all data just let me know and i will be happy to post. I have updates through to 2008.

Thanks
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Old 04-23-2011, 06:24 PM
Corey's Auto Corey's Auto is offline
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also i have mitchell to 2005. sometimes much better info than alldata it just depends
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  #5  
Old 04-24-2011, 01:23 PM
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Ok. This is exactly what I did before and I understand that the gases are sucked not pushed.

Are the blow-by gases produced continuously when the engine is warm and running?

Do they need to reach a certain pressure before they are let in the intake ?

If not, because the gases are produced continuously -> the pcv is slightly open continuously( if there is a perfect seal in the crankcase) so the gases can be let into the intake?

If there is a leaking gasket the pcv will close so it does not let the blow by gases to the intake? and this makes the rough idle?





Quote:
Originally Posted by Corey's Auto View Post
The only way air can enter the crankcase is due to blowby or a leaking seal/gasket.
What about the air pump? From my understanding it does take filtered air and is pushing it, into the crankcase when the engine is cold. Is this I guess to back-up the lack of blow-by gases which are produced when engine warm only? Or I can't see well enough and the pipes are going in the cylinder head to push the air in the exhaust system to lower the emissions when engine is cold?

Last edited by joyism5; 04-24-2011 at 01:53 PM. Reason: spelling
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Old 04-24-2011, 05:51 PM
GLHExorcist GLHExorcist is offline
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Great info! This promts me to try my solus pro on my car as it runs like crap right now...
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Old 04-24-2011, 06:17 PM
Corey's Auto Corey's Auto is offline
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Ok, I will try to answer in order. Blow by gasses are normally produced all the time but the actual amount of air will be very small. For this reason yes the ccv will be open most of the time. And yes the amount of vacuum in theory will determine how far the ccv will open (at idle it will open less.) However, this is where it differes because it really makes no difference how far the ccv opens or not. It should only have available the blowby gasses to pull through. And in a hypothetical case where an excessive amount of blowby was being produced the ccv would be able to open as far as it needed due to the pressure difference.

If there is a leaking gasket the ccv will already be open. The difference is that the leaking gasket will allow fresh unmetered air to flow through the ccv causing a rough idle. This was the main thing I was trying to point out. Leaking valve cover gasket = vacuum leak. (Very strange thing to see in the design of an engine. Other cars are not like this.)

As for the air pump, on the M62 engines the air pump is only on the vanos engines. The air pump has nothing to do with vacuum leaks or the ccv. The air pump is there to pump air into the exhaust pipes in order to heat up the catalytic converter faster during warm up. (The cat needs to heat up before it starts working.) This is also the reason why bmw automatic transmissions have very late/higher rpm shifts when cold. (To get the cat warmed up.)
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Old 04-24-2011, 06:25 PM
Corey's Auto Corey's Auto is offline
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Just wanted to add that the air pump puts air into the exhaust not to lower temps but to raise them. More oxygen = higher cat temps. (Just like stoking a fire) This is also why cats fail prematurely due to vacuum leaks such as the hypothetical valve cover leak.

Valve cover gasket leak --> unmetered air through ccv --> super lean fuel mixture --> too much oxygen in exhaust due to lack of fuel --> very very hot catalytic coverter, often melting the substrate or at least breaking it apart --> catalyst inefficiency codes and possible restricted exhaust
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Old 04-25-2011, 08:07 AM
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joyism5 joyism5 is offline
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Thanks for letting me understand better how this system actually works. I got it clear and light now. So gases are sucked in the intake and if there is a leak in the crankcase, it will make the lean mixture.
When I first start to fix this issue and read it I got it a little wrong :I thought that the the blow-by gases produce such a big amount of pressure that the pcv will be open all the time, when actually the blow-by are produce in such a small amount and the pcv is more closed than open . Because of the design I thought that the air pipe is going in the crankcase, not in the cylinder head/exhaust port. And again I couldn't find the right information for it.

Thanks again .

Last edited by joyism5; 04-25-2011 at 08:11 AM. Reason: speelling
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Old 04-25-2011, 11:48 AM
Corey's Auto Corey's Auto is offline
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Thank you I'm glad I could help. Also, just to clarify, the metal pipe connecting to the ccv does go to the crankcase. If your engine uses an air pump, which the pre vanos m62 does not, then the air pump will be pulling fresh unmetered air and pushing it into the exhaust manifold, not the head. (the silver disk looking thing sticking up from the exhaust manifold, usually has a vaccum line attached to it)
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Old 04-25-2011, 11:53 AM
Corey's Auto Corey's Auto is offline
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air pump has nothing to do with how the engine will run normally. it is a completely separate system. if there was a fault and the air pump would have to malfunction in 2 ways to affect the engine. the pump would have to turn on, and the port on the ex manifold would have to open. if this happened (very unlikely), then your short term fuel trim might show up as lean, causing more fuel from the dme, causing too rich a fuel mixture and rough idle. this is easily tested though by actuating the valve on the exhaust manifold with a vacuum pump tool.
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Old 04-25-2011, 04:45 PM
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Quote:
Originally Posted by Corey's Auto View Post
Also, just to clarify, the metal pipe connecting to the ccv does go to the crankcase. If your engine uses an air pump, which the pre vanos m62 does not, then the air pump will be pulling fresh unmetered air and pushing it into the exhaust manifold, not the head. (the silver disk looking thing sticking up from the exhaust manifold, usually has a vaccum line attached to it)
Yeah that aluminum pipe does go in the OSV/crankcase like in pic 1.

My engine is M62 TU (vanos) and I was referring at the pipe that goes in both cylinder heads close to the exhaust manifold not straight into it. This pipe is aluminum too and has the valve which opens to let the forced air in the cylinder head. That's why I got confused , looks like is going in the crankcase but it goes actually in the cylinder head .
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Last edited by joyism5; 04-25-2011 at 04:55 PM.
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Old 04-25-2011, 05:27 PM
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Quote:
Originally Posted by Corey's Auto View Post
if there was a fault and the air pump would have to malfunction in 2 ways to affect the engine. the pump would have to turn on, and the port on the ex manifold would have to open. if this happened (very unlikely), then your short term fuel trim might show up as lean, causing more fuel from the dme, causing too rich a fuel mixture and rough idle.
This actually did happen't to me and I had no rough idle . I run the car for several months like that. Air pump was fried . I have read that brushes in it goes bad pretty often. My pump was not serviceable.
The SES light came on and codes 0171 & 0174 system lean bank 1 and bank 2 showed up. Very close to those codes for the MAF when it goes bad 1171 & 1174 - Fuel Trim Adaptation Additive Bank 1& Bank 2 Malfunction.
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Old 01-03-2012, 03:01 PM
carl0s carl0s is offline
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Quote:
Originally Posted by Corey's Auto View Post
This is my first post, I just wanted to clarify the operation of the ccv valve (this applies to the 5 and 3 series as well.) I've read many posts in the past on how to tell if yours is bad and how to replace, but I thought I might share a little info that will help with vacuum leak diagnostics when the ccv is in fact good. I see the problem quite frequently in my shop.

The ccv valve used in bmw engines works very differently than almost any other design. Most ventilation valves allow a predetermined flow of fresh air through the engine crankcase to prevent acidic vapor buildup from blowby. The amount of air is often dependent on intake manifold vacuum. The ccv on the other hand is designed to ONLY open when there is an ABSENCE of vacuum in the crankcase. The diaphram in the ccv will be fully open upon startup for a brief second until engine vacuum accumulates in the crankcase, at which point the valve will then close. If your crankcase is not completely sealed with a perfect airtight seal at all gaskets, the ccv WILL open and create a vacuum leak. BMW engineers designed the valve to only open to permit blowby to be sucked into the manifold, there is no fresh air/breather intake into the crankcase.

What all this means is that if you have a rough running engine and a known good ccv valve and maf, the first thing you should do is check the short and long term fuel trims. You can use almost any scan tool with live data for this. The combined long and short term fuel trims for our cars should end up somewhere between -3 and +3. Often I will see 02 sensor out of range codes and maf sensor codes on an engine with a rough idle. If you check you will often find a long term fuel trim of 0 (due to the 02 sensors being out of range), and a short term fuel trim of 25 or close to it. 25 indicates the dme is trying to add fuel to a very lean mixture. At 25, the dme is already at its limits as far as trim goes. This often indicates leaking valve cover gaskets creating a vacuum leak which allows the ccv to open when it otherwise shouldn't.

Also don't forget that you can also have leaky gaskets on the intake side that will cause high fuel trim values. A great way to track them down if you see the fuel trim way off is to spray all around the intake manifold and valve covers with starting fluid while the engine is running and listen for changes in the rpm and how the engine runs. A large leak or crushed valve cover gasket will become very apparent. I have even seen new valve cover gaskets that were installed improperly by crushing or twisting the gasket without realizing it. These might even run fine for a while until the leak grows and gets big enough that the dme can no longer compensate for it.

Also, after you replace the failing gasket, make sure you unplug your battery for 10 minutes to reset the long term fuel trims, otherwise it will most likely still run pretty rough and be way too rich. Or if you have carsoft or a gt1, just reset the fuel adaptation values.

Please forgive me if any of this information has already been mentioned by others before. I just wanted to write an article and share my experience. Thanks

Hey. Thanks for the informative post. You describe my symptoms (fuel trim) perfectly.
I have been trying to track down vac leaks on my e46 330i for a few weeks now. I already replaced the valve cover gasket, oil filter housing gasket and both intake boots. All of which were badly perished.

Up until today, I was seeing +28 at idle on the short term fuel trims (but 0 on the long terms.. this confused me, but you say that's expected..). This was triggering the "system too lean" codes.
Thanks to a post on another forum, I discovered that the lower oil separator -> dipstick hose was fractured ( see http://forum.e46fanatics.com/showthread.php?t=773551 ). Mine looked like this:

After replacing this hose today, I am now seeing short term fuel trims hovering around 11 - 14% at idle.

Obviously this is much better, and will not trigger the "system too lean" codes, but I think this means I still have a small vac leak. I guess due to the size of the vac leak that it only affects idle mixture, and actually the car appears to run fine, but I want everything to be as it should be because the car has an LPG (autogas) conversion that is also problematic, but I want to make sure the petrol side is perfect before attempting to fix the autogas side.

I will be buying some starter fluid tomorrow, and I have already checked the air-distributor O-rings, and I have a throttle-body gasket here, but I don't think that is necessary..

Any other ideas where to look for small leaks?

I must say that I can hear intake hiss from the top of the engine (intake mani) roughly around about where the CCV / oil separator is (just forward of the DISA valve). I'm not sure if this is normal for this engine though. I've only had it a month.. I bought it in a bad state

The weather is so bad here right now that I doubt I will be able to replace the CCV itself within the next month. Maybe after next month when I have a garage to work from. So any other ideas would be most welcome.

I have a small amount of suction/vacuum from the oil filler hole, and dipstick hole. Nothing very noticable. I haven't actually checked the pressure but I suspect it's nice, and gentle, like it should be, so not a classic case of failed CCV, but I dunno ?

Thanks a million,
Carl

Last edited by carl0s; 01-03-2012 at 05:02 PM.
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Old 01-04-2012, 02:59 PM
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I don't recall to see that kind of hose on the V8. Maybe, on the secondary air pump. I see on your profile that you are driving an E46. This is the E38 section of the forum.....you might want to re-post on the E46 section, or there's even more activity on the E39 side of the house. Maybe you will get a faster answer. Indeed the straight 6 engine has those hoses for the crankcase ventilation system.

QUOTE :

I must say that I can hear intake hiss from the top of the engine (intake mani) roughly around about where the CCV / oil separator is (just forward of the DISA valve).

You are talking about the straight 6 engine for sure....
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Old 01-04-2012, 03:10 PM
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Thank you I'm glad I could help. ..... then the air pump will be pulling fresh unmetered air and pushing it into the exhaust manifold, not the head.
The air pump does push fresh unmetered air into the cylinder head , (not the exhaust manifold). The exhaust ports of the cylinder head will direct the fresh air right on the exhaust valves. See in the attached picture the tiny hole where the exhaust valve has been removed.
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Old 01-04-2012, 03:28 PM
carl0s carl0s is offline
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Quote:
Originally Posted by joyism5 View Post
I don't recall to see that kind of hose on the V8. Maybe, on the secondary air pump. I see on your profile that you are driving an E46. This is the E38 section of the forum.....you might want to re-post on the E46 section, or there's even more activity on the E39 side of the house. Maybe you will get a faster answer. Indeed the straight 6 engine has those hoses for the crankcase ventilation system.

QUOTE :

I must say that I can hear intake hiss from the top of the engine (intake mani) roughly around about where the CCV / oil separator is (just forward of the DISA valve).

You are talking about the straight 6 engine for sure....
Yes I am but my post was directed at the OP, since his diagnostics explanation is relavent to my situation (short term fuel trim behaviour, vac leak through the CCV). This is all pretty general BMW stuff, or so it seems (my previous experience is Toyota & GM)

I will be checking the state of a couple of vacuum caps at the weekend anyway, that might cover it.

thanks,
Carl
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Old 01-04-2012, 05:39 PM
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Yes I am but my post was directed at the OP,

I have not seen the "OP" in months , here on the forum. If you want a reply from him, try send him a PM.

This is all pretty general BMW stuff, or so it seems
thanks,
Carl
Indeed is general stuff for BMW. A little bit different design on the V8. Read this thread and you might find your answers : http://www.bimmerfest.com/forums/sho...005&highlight=

There are a lot of vacuum test for the straight 6 engine on the E39 section.

http://www.bimmerfest.com/forums/sho...452&highlight=

http://www.bimmerfest.com/forums/sho...d.php?t=588505


Good Luck !
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Old 01-04-2012, 06:07 PM
carl0s carl0s is offline
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Quote:
Originally Posted by joyism5 View Post
Indeed is general stuff for BMW. A little bit different design on the V8. Read this thread and you might find your answers : http://www.bimmerfest.com/forums/sho...005&highlight=

There are a lot of vacuum test for the straight 6 engine on the E39 section.

http://www.bimmerfest.com/forums/sho...452&highlight=

http://www.bimmerfest.com/forums/sho...d.php?t=588505


Good Luck !

Thanks very much
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Old 04-10-2012, 09:11 AM
jasony1 jasony1 is offline
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[QUOTE=Corey's Auto;6014045]This is my first post, I just wanted to clarify the operation of the ccv valve (this applies to the 5 and 3 series as well.) I've read many posts in the past on how to tell if yours is bad and how to replace, but I thought I might share a little info that will help with vacuum leak diagnostics when the ccv is in fact good. I see the problem quite frequently in my shop..............]

Very good information regarding CCV system!

Here is my question:
My 2005 X5, 4.4 (N62), 83K, started to comsume oil recently, I inspected the CCV, one of the rubber seal is harden, could not seal properly. and replaced both of them ($25/each from dealer, Parts# 11 12 7 547 058). The engin runs very smooth.

After reading all of these posts here, I made a pressure gauge to measure the vaccum in crankcase. It is 10 in of water.
Read other post, said it should be around 5" of water.
And I block one of vaccum hose from intake to CCV, pressure still at 10", and blocked the other one, it is same.

It seem to me that booth new CCV works properly and regulate the vaccum at 10" of water.

Question: Is this N62 engine, designed to higher vaccum than others? Or this new design of CCV regulate the crankcase pressure at the high vaccum?

Also, it seem to me that the CCV is pressure regulator, it is not an on-off shut valve, rather, it continous open all the time with different flow per the force pushed on the valve seat, the higher vaccum at crankcase, the higher force to overcome the spring to reduce the gas flow rate.
This would regulate the crankcase pressure at pre-set level (set by the spring force of the CCV).

Any input would be appreciated
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Old 05-07-2012, 02:40 AM
irvs740il irvs740il is offline
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This is excellent information....i'm hoping it can aid me in diagnosing my e38 issue...... Smokes at start up, oil in intake manifold, oily plugs, threw codes 0135, 1174, 1175 plus the misfire ones 0301-0304.... Replaced rear OSV but now I'm getting the suction at dipstick along with howling from intake plus all previous symptoms. I replaced all seals on intake as well as vent pipe, old one deteriorated rubber section. So now I'm confused...... I'm leaning towards the cyclone separator but dont want to take it apart for the heck of it........ ????? Thanks
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  #22  
Old 05-09-2012, 07:48 PM
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joyism5 joyism5 is offline
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I think is the OSV. There is a plastic piece that connects the OSV to an elbow which usually breaks. Check around for OSV threads, I post somewhere some pictures with mein when it broke. Same symptoms.
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Old 05-09-2012, 08:23 PM
irvs740il irvs740il is offline
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Thanks....do you mean the elbow inside behind the timing covers......?

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Originally Posted by joyism5 View Post
I think is the OSV. There is a plastic piece that connects the OSV to an elbow which usually breaks. Check around for OSV threads, I post somewhere some pictures with mein when it broke. Same symptoms.
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Old 05-10-2012, 06:58 PM
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Yes. Read post #11 here: http://www.bimmerfest.com/forums/sho...d.php?t=577207
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Old 05-11-2012, 04:06 AM
irvs740il irvs740il is offline
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Thanks Joy....... I'm pretty confident now that its the oil separator behind covers......while I'm in here what's the best way to remove carbon deposits on valves in intake side....?
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