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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 7 Series / 8 Series > 7 Series - E65 / E66 (2002 - 2008)

7 Series - E65 / E66 (2002 - 2008)
Discussion of BMW's 4th generation E65/E66 7 Series flagship. The E65 generated much controversy, due to its radical styling and iDrive user difficulties. Nonetheless, the E65 broke records to become the best-selling 7-series iteration ever, especially after its 2005 facelift.

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  #1  
Old Yesterday, 01:46 PM
750er-CA 750er-CA is offline
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Location: toronto
 
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Mein Auto: 750i
Cyl 1 compression loss during valve seals work

Hello guys,

I've been changing valve stem seals last few days on my e65 '06 n62 engine and have a problem with a cylinder 1 (bank 1).
This is the first cylinder I started working on.

I pressurized the cylinder to 90psi and during the removal of the old seal from the intake valve I sprayed some carburetor cleaner on it coz it stuck really hard. At the time I was trying to put valve keepers on I lost one piece so I had to let it stay without coil overnight.
Then I continued working on all the other cylinders of bank 1 and everything went smooth.

Next morning I bought some extra keepers from the dealer and tried to pressurize the #1 cylinder again to put the coil on. All I could get is 10psi!
The crankshaft is in the TDC with the pin in and the camshafts are removed.

I'm 100% sure I couldn't have bent the valve. I rotated it accidentally, could this affect the compression?

I have read many of you guys changed the valve seals here. Did you ever have the similar problem? I'm really afraid to put the timing cover on without solving this issue.

Any thoughts?

Last edited by 750er-CA; Yesterday at 08:05 PM.
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  #2  
Old Yesterday, 01:50 PM
750er-CA 750er-CA is offline
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Location: toronto
 
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Mein Auto: 750i
Could the carb. cleaner wash the oil away from piston rings and lower the compression? or the problem is with the valves?
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  #3  
Old Yesterday, 09:18 PM
dvanlare dvanlare is online now
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Mein Auto: '95 840Ci, '05 745Li
I feel your pain. The cylinders near the firewall are the worst to work on. I too had one keeper that didn't seat well and shot out like a bullet when I released the spring tension. Luckily it was early enough in the day for me to run to the dealership and leave the cylinder pressurized while I got the new keepers. You probably just have a little carbon buildup on the valves making it difficult to get a perfect seal. I also lost compression a few times when moving from one valve to the next. Most of the time I could just let it sit for 30 minutes with the spring applying pressure to the valve and it would reseat well enough to re-pressurize the cylinder. A few times I had to rotate off and back on to TDC to get it to reseat. In your case make sure the other 3 valves are properly seated and try to simultaneously pull up on your last valve while pressurizing the cylinder. If that doesn't work you may have to try to carefully compress the spring without pushing the valve in and then carefully add the keepers using the glob of grease on the end of the screwdriver method. Good luck!
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Old Yesterday, 09:47 PM
750er-CA 750er-CA is offline
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Location: toronto
 
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Hi dvanlare,

Thanks a lot for the tips buddy!

I checked all 4 valves one by one on the problematic cylinder once again.
Removed the spring and rotated each valve to make sure there is no carbon pieces stuck between valve head and the seat.
Then I pressurized the cylinder while trying to push the valve in to check if there is no leaks.
Each valve seats really tight on its place and I can hear the air goes down to the engine while compressor is working.
I'm sure the valves are ok.
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  #5  
Old Yesterday, 09:53 PM
750er-CA 750er-CA is offline
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Location: toronto
 
Join Date: Aug 2015
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Mein Auto: 750i
Update.

I sprayed a tablespoon of engine oil on top of the piston using a syringe with a small attached hose from my brake bleeding kit. Rotated the crankshaft 2 times and whoa the compression is back again.
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