When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Oil pool in cylinder 4 after having a borescope done, 5&6 have oil towards the head
Cylinders 1,2,3 look pretty normal
Very small amount of smoke at start up but not all the time
100-200 ml of oil every 600 miles
No CEL or noises
Cylinder 4,5,6 relined 20k miles ago after found to have had bore scoring
No evidence of AOS being changed
If you had your engine re-sleeved with iron or steel liners they have a different thermal expansion rate than aluminum, hence I believe they require a larger piston to cylinder clearance.
Its one of the reasons Porsche try and match piston to cylinder material expansion to keep this tight, reduce emissions and oil consumption.
It might be normal but I'm sure an expert will comment soon
Oil pool in cylinder 4 after having a borescope done, 5&6 have oil towards the head
Cylinders 1,2,3 look pretty normal
Very small amount of smoke at start up but not all the time
100-200 ml of oil every 600 miles
No CEL or noises
Cylinder 4,5,6 relined 20k miles ago after found to have had bore scoring
No evidence of AOS being changed
101k miles
Anyone seen similar condition of cylinders?
I just borescoped my engine which has about 15k kms post rebuild. I have been burning a lot of oil but i have attributed it to the AOS. My cylinders look like yours from the spark plug holes and there is a lot of carbon on the pistons from the burnt oil. From the sump i can see a pool of oil behind the piston which the rings seem to be largely holding back from the combustion chamber. You should measure AOS health with a vacuum manometer.
I just borescoped my engine which has about 15k kms post rebuild. I have been burning a lot of oil but i have attributed it to the AOS. My cylinders look like yours from the spark plug holes and there is a lot of carbon on the pistons from the burnt oil. From the sump i can see a pool of oil behind the piston which the rings seem to be largely holding back from the combustion chamber. You should measure AOS health with a vacuum manometer.
Please share with us your manometer readings causing you to condemn your AOS too "burning a lot of oil"
What type of rebuild did you do. Nik'd alum or steel..?
Charles of LN Engineering stated that the non-Porsche piston rings are not keyed to the pistons so that the ring gaps can turn and end up where the oil would leak to the combustion chamber. That is one reason why a LNE rebuild can consume oil.
Please share with us your manometer readings causing you to condemn your AOS too "burning a lot of oil"
What type of rebuild did you do. Nik'd alum or steel..?
Sleeves are nickasil aluminum. Originally I had 3.25" water column. When I unplugged the Vacuum to the AOS for the blow by test I had exceptionally low blow by so I suspected a vacuum leak. I found two leaks in the cross over aos tube going to bank 2. One at the elbow and one at the aos or very close. You can find the area of the leak by finding the oily residue. Assuming no leaks in your aos your vacuum should be in the 4-6" water range. Fixing the elbow leak moved my vacuum to 3.75" despite there being another leak at the aos. I'm replacing it because I am not going that far to leave a 7 year old aos and only replace a hose. Not 100% certain the aos is at fault but I know my main line has leaks so I am changing it to the UAOS solution. Injectors will be changed too despite them having been tested.
His post is like 6 years old, What you wanna bet he's sold the car?
For what it's worth, your "pool of oil" may actually be a byproduct of leaking fuel injectors.
I am replacing them to rule it out. They were cleaned and tested. For every other car that is sufficient but for m96 engines everyone says to junk them. I'll have new ones in shortly.
Charles of LN Engineering stated that the non-Porsche piston rings are not keyed to the pistons so that the ring gaps can turn and end up where the oil would leak to the combustion chamber. That is one reason why a LNE rebuild can consume oil.
BTW : Anyone who has oil pooling in the combustion chamber or intake should ( first) test the AOS Health ( second ) Test the Engine Health / blow-by ( I don't care if it a newly rebuilt engine with cylinders/rings/pistons and only 10k miles, test it )
09-10-2018, 05:41 PM
Oil in Cylinders
