High oil consumption and alusil cylinder liners
Discussion
Hi I'm reasonable sure your efforts whilst thorough will not cure your oil consumption issues, unless you have a major breather issue which I think you will have investigated before tare-down. your ring bore seal has been compromised and will not rectify it's self, true your worn exhaust guides could pass oil but that is not your issue here.
True your injectors could have caused bore wash and replacing the faulty ones addresses one issue, it will not fix the ring/bore issue, this has been done and it will not correct itself. It's been debated much for years piston ring bore seal is critical and the window of getting it right is very small, once out of that window it rarely corrects itself.
Once an oil burner always an oil burner until you address the cause and replace the rings/bore finish accordingly. At least your head rework will not be in vane should you decide/ need to pull the motor to correct the bore issues, which I suspect you have had in the back of your mind anyway.
True your injectors could have caused bore wash and replacing the faulty ones addresses one issue, it will not fix the ring/bore issue, this has been done and it will not correct itself. It's been debated much for years piston ring bore seal is critical and the window of getting it right is very small, once out of that window it rarely corrects itself.
Once an oil burner always an oil burner until you address the cause and replace the rings/bore finish accordingly. At least your head rework will not be in vane should you decide/ need to pull the motor to correct the bore issues, which I suspect you have had in the back of your mind anyway.
The bore wear measurements you gave were not very helpful. Rather than relative taper and ovality what we need is absolute measurements versus nominal in both planes and at three positions, top, middle and bottom. However with pistons in you can only really give top and middle. Also on the thrust plane (90 degrees to crank axis) whether there is any measureable wear ridge from just above where the top ring comes to which will be unworn and then just below that.
I'm adding 1 litre of oil every ~2,000 miles to my 148k N53 330i.
Very worried after reading this thread. I've got an ongoing cold start misfire issue throwing combustion misfire codes ( http://www.pistonheads.com/gassing/topic.asp?h=0&a...).
Brilliant write up, good luck with your fix. I will watch for updates.
Very worried after reading this thread. I've got an ongoing cold start misfire issue throwing combustion misfire codes ( http://www.pistonheads.com/gassing/topic.asp?h=0&a...).
Brilliant write up, good luck with your fix. I will watch for updates.
Got everything reassembled and running last night. With new injectors coded up and refreshed head it's running super smooth. It's going to be a couple of hundred miles before I know if there has been any significant impact to oil consumption, I'll report back as soon as I have some more info to share.
bmwmike said:
Cool!
What did you do about the oval cylinders? Or were they not that bad?
Any chance of a vid of it idling? Am sad like that
Cheers
I didn't touch the bottom end, and the measurements I took didn't indicate that there was any major distortion, as best as I could tell. Surfaces also didn't show any signs of scoring or abnormal wear.What did you do about the oval cylinders? Or were they not that bad?
Any chance of a vid of it idling? Am sad like that
Cheers
Video of cold start idle at the bottom especially for you bmwmike :-)
Edited by viperbluecerb on Monday 30th May 10:26
bmwmike said:
Were yours coked up much?
They weren't really bad compared to some of the pictures I have seen, but they weren't good either, with fairly thick layers of carbon on the back of the valves and stems. If I hadn't had the cylinder head off and I just wanted to de-coke, I would probably walnut blast the intake ports. From what I have read it seems the only good way to do it while the engine is still assembled.
http://blog.modbargains.com/get-nuts-feed-bmw-n55-...
After 1K miles, it is unfortunate but not unsurprising that I must report that the oil consumption continues. It was always a strong possibility that the issue was ring/bore related and after all the work that I have undertaken, this has proven to be the case. Slightly overfilling led to a longer that expected time for the oil level gauge to report a drop in oil level and then it continued at the previous rate. Generally running very well with a stable idle and no visible smoke under any observed conditions.
The next step would be to completely pull the engine and rebuild/replace the bottom end. While my pockets run reasonably deep, I am not sure that for this problem they run that deep. Realistically it is another 4K+ to completely rebuild the rest of the motor with a new block and pistons and everything else that will be done should I choose to do so.
Hope the thread helps others in any way they choose to draw from it.
The next step would be to completely pull the engine and rebuild/replace the bottom end. While my pockets run reasonably deep, I am not sure that for this problem they run that deep. Realistically it is another 4K+ to completely rebuild the rest of the motor with a new block and pistons and everything else that will be done should I choose to do so.
Hope the thread helps others in any way they choose to draw from it.
Edited by viperbluecerb on Sunday 29th May 11:50
Edited by viperbluecerb on Monday 30th May 10:28
This is probably one of the most helpful threads I have come across on BMW oil consumption. Thank you for taking the time and money to look into it!
Here is my issue: http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Reading online a few forums have also stated that the oil rings are thin and become carbonised quickly. Anyhow I am trying out Liqui Moly Cera Tec. My theory is that it will address any micro imperfections in cylinder walls if it is the case. It's hard to tell just yet. I added it to existing oil. I had fresh oil in January and it's done 2147 miles since then - at which point it requested a litre top up.
Last year I was on the cusp of the tolerance and the warranty claim was denied which was frustrating. Mine has the oil separator built in so it is not a standalone serviceable part. I stsrted to change oil more regularly and it improved the consumption.
My compression checks out, leak down tests and oil analysis did not present any concerns.
Here is my issue: http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Reading online a few forums have also stated that the oil rings are thin and become carbonised quickly. Anyhow I am trying out Liqui Moly Cera Tec. My theory is that it will address any micro imperfections in cylinder walls if it is the case. It's hard to tell just yet. I added it to existing oil. I had fresh oil in January and it's done 2147 miles since then - at which point it requested a litre top up.
Last year I was on the cusp of the tolerance and the warranty claim was denied which was frustrating. Mine has the oil separator built in so it is not a standalone serviceable part. I stsrted to change oil more regularly and it improved the consumption.
My compression checks out, leak down tests and oil analysis did not present any concerns.
It's shame you didn't get a happier outcome. I really can't see why a light reconditioning of the bores and a new set of rings wouldn't resolve this.
http://www.sunnen.com/NewsDetails.aspx?NewsID=11
http://www.sunnen.com/NewsDetails.aspx?NewsID=11
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