Service Engine Light - BMWNA says its a Crank Case Pressure issue..?

drew4392 · 06-04-2011, 10:18 AM

So, this is the 4th (or 5th?) time my CPO '07 335 has been in to the dealer in less than a year due to a service engine light. Each time they change the HPFP and something else (coils and injectors one time, plugs another, plugs and clean valves another.....etc).

This time, again, they installed a new HPFP. But, it didn't cure the problem. So it went to BMWNA for investigation. BMWNA came back and suggested the dealer check the crank case pressure. The pressure was low. So, they plan on changing the valve cover gasket to see if that returns pressure to normal levels.

As soon as I hung up with my SA, I thought, wouldn't there be an oil leak if there was a pressure leak of any kind in that area?? What do you all think? I'm starting to feel like they don't know what is wrong. But I hope I'm wrong and BMWNA will fix this.

Thoughts?

Thanks, all

bahn stormer · 06-04-2011, 11:06 AM

Crankcase pressure is exerted on the area including oil pan, up under pistons (crankshaft area), as well as oil drainage passages up to and including the area under the valve cover. If there there was an external leak and crankcase was pressurized you would not necessarily see a leak.

1. The PCV system maintains a pressure band that is slightly positive. (just a couple inches of H2O pressure)
2. If you are tuned you will run a pressure that is less positive or even a slight vacuum.
3. If you have an OCC it will tend to counter act this and push it more positive.
4. I have never heard of a code from crankcase pressure and am not aware there is even a sensor that monitors this.
5. Dzenno did some extensive testing on this, though with RB turbos.
http://www.e90post.com/forums/showthread.php?t=518306

Not sure what you want now but theres some crankcase info.

drew4392 · 06-04-2011, 12:20 PM

Thank you for the thoughtful response. I know a lot more than I did a few minutes ago. Guess my idea about leaking oil is possibly wrong. I was really looking to confirm or dispell that idea. Now ill wait for the dealer to tell me what part the bottle spins and points to next.

Btw, the crankcase pressure theory wasnt because of the light. They said the light doesn't give them specific info. They need to guess on a lot of this stuff

therealm3 · 06-04-2011, 03:35 PM

Quote:

Originally Posted by drew4392

They need to guess on a lot of this stuff

Rather ironic choice of words. :-) Modern dealer techs are so reliant on the code scanner and computer that they don't do any old shcool investigation anymore. Throwing parts at a car is cheaper for them in the long run. oh well what can you do. good luck with the repairs.

drew4392 · 06-08-2011, 09:28 PM

Here's an update... dealer replaced the valve cover gasket (per BMWNA's direction) to see if that would replenish crank case pressure. NOPE. So now they are back to the drawing board. BMWNA is now suggesting to replace the oxygen sensor to see if the reading is simply incorrect.

Apparently, there is too much oxygen in the system. Per my SA.

The waiting game continues. It's been 1 1/2 weeks.

** @ Bahn Stormer - I think you were right in that there is no crank case pressure sensor, per se. He changed his story to say there is too much oxygen in the system. Not sure if that is the same as too little crank case pressure (I would think too much pressure...).

Really thinking about having BMWNA buy this thing back....

06-04-2011, 10:18 AM	#1
drew4392 Second Lieutenant 51 Rep 238 Posts Drives: '07 335i Sedan Join Date: May 2010 Location: Los Angeles iTrader: (1)	Service Engine Light - BMWNA says its a Crank Case Pressure issue..? So, this is the 4th (or 5th?) time my CPO '07 335 has been in to the dealer in less than a year due to a service engine light. Each time they change the HPFP and something else (coils and injectors one time, plugs another, plugs and clean valves another.....etc). This time, again, they installed a new HPFP. But, it didn't cure the problem. So it went to BMWNA for investigation. BMWNA came back and suggested the dealer check the crank case pressure. The pressure was low. So, they plan on changing the valve cover gasket to see if that returns pressure to normal levels. As soon as I hung up with my SA, I thought, wouldn't there be an oil leak if there was a pressure leak of any kind in that area?? What do you all think? I'm starting to feel like they don't know what is wrong. But I hope I'm wrong and BMWNA will fix this. Thoughts? Thanks, all
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06-04-2011, 11:06 AM	#2
bahn stormer Lieutenant 11 Rep 529 Posts Drives: 07 E90 335i 6MT, 65 MGB Join Date: Feb 2008 Location: PA iTrader: (3)	Crankcase pressure is exerted on the area including oil pan, up under pistons (crankshaft area), as well as oil drainage passages up to and including the area under the valve cover. If there there was an external leak and crankcase was pressurized you would not necessarily see a leak. 1. The PCV system maintains a pressure band that is slightly positive. (just a couple inches of H2O pressure) 2. If you are tuned you will run a pressure that is less positive or even a slight vacuum. 3. If you have an OCC it will tend to counter act this and push it more positive. 4. I have never heard of a code from crankcase pressure and am not aware there is even a sensor that monitors this. 5. Dzenno did some extensive testing on this, though with RB turbos. http://www.e90post.com/forums/showthread.php?t=518306 Not sure what you want now but theres some crankcase info.
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06-04-2011, 12:20 PM	#3
drew4392 Second Lieutenant 51 Rep 238 Posts Drives: '07 335i Sedan Join Date: May 2010 Location: Los Angeles iTrader: (1)	Thank you for the thoughtful response. I know a lot more than I did a few minutes ago. Guess my idea about leaking oil is possibly wrong. I was really looking to confirm or dispell that idea. Now ill wait for the dealer to tell me what part the bottle spins and points to next. Btw, the crankcase pressure theory wasnt because of the light. They said the light doesn't give them specific info. They need to guess on a lot of this stuff
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06-08-2011, 09:28 PM	#5
drew4392 Second Lieutenant 51 Rep 238 Posts Drives: '07 335i Sedan Join Date: May 2010 Location: Los Angeles iTrader: (1)	Here's an update... dealer replaced the valve cover gasket (per BMWNA's direction) to see if that would replenish crank case pressure. NOPE. So now they are back to the drawing board. BMWNA is now suggesting to replace the oxygen sensor to see if the reading is simply incorrect. Apparently, there is too much oxygen in the system. Per my SA. The waiting game continues. It's been 1 1/2 weeks. ** @ Bahn Stormer - I think you were right in that there is no crank case pressure sensor, per se. He changed his story to say there is too much oxygen in the system. Not sure if that is the same as too little crank case pressure (I would think too much pressure...). Really thinking about having BMWNA buy this thing back....
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