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Discussion Starter #1
Hello M5 board, Mr. P asking if anyone knows reason for bore issues on the S85?

Recently purchased for a rebuild and Cyl#8 and Cyl#10 are terrible.

Also noticed an e-bay seller trying to sell block/crank with similar issues, so this must be an issue.

pics attache, want to know root cause.

Mr. P
 

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Injectors can fail on these cars, maybe could’ve been a fuel wash scenario? The more experienced here will chime in soon
 

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That looks like a specific failure not a general failure. Something wiped out the rings like fuel wash down as suggested above.
 

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Seems like broken ring land or piston led to the ring heavily scoring the walls in just a few areas. Could have been piston damage resulting from detonation localized in that part of the piston...Pure bore wash wear that I've seen looks a bit different, it doesn't go the whole way of the stroke and is more of a burnished area often some what inline with where excess fuel would accumulate. The location of the wear on 10 doesn't seem to be consistent with that failure mode at all.

Was that disclosed when you bought the block? Did the pictures show this in the auction? Not sure that the block can be salvaged unless a bore liner is installed but that may be more than what another undamaged block would cost.
 

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Discussion Starter #8
Hello M5 board, Mr. P asking if anyone knows reason for bore issues on the S85?

Recently purchased for a rebuild and Cyl#8 and Cyl#10 are terrible.

Also noticed an e-bay seller trying to sell block/crank with similar issues, so this must be an issue.

pics attache, want to know root cause.

Mr. P
Hello M5 Forum and thank you for ideas.

I do not believe head-gasket failure. It is MLS and no signs of blow-by including examination of heads and block mating surface. Also no "steam cleaning" of pistons, and my bore issues are on Cyl#8 MAJOR and Cyl#10 BAD.

Do not know, but overheating not currently being considered....bank 2, cyl 8 and 10 only, no other signs of overheating.

Injector wash.......Maybe.....did not isolate injectors by cylinder, but can get them tested for failure.

Do not have full history of engine, but recently learned it has been out of vehicle for ~5yrs. This would not have any issue on bore, but explains corrosion....but not "mud" in valve train. Bottom end has worn bearings, but not "spun" or signs of excessive heat on caps/crank.

Looks like bore scaring started along axis of crank which is weird as I would expect must damage perpendicular to piston movement. Could this possibly be result of crank-shaft thrust bearing gone awry? Will have crank out next week and can confirm>>>>

NOTE: Bank 1 now included, had "mud" in cylinders and head, but no apparent bore damage.

Thank you ALL again for comments and I will try to get some more pictures in the next few days.

Mr. P
 

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Hi!
This is very similar to how my block looked after pouring 20L of fuel out when chainging oil...

I gotta go for injector failure leading to hydrolock, killing the rings and giving scaring.. And I think The 9cyl is The result of injector at cyl 8 spillning over doing same, but less damage to 9th cyl.
 

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What are your plans for the block? Bore it out for a stroker? The cost to get it back to factory spec has got to be close to building a stroker especially with it already gutted. Guess you could also make a nice coffee table.
 

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Discussion Starter #11
lol, and I was thinking a tall end table!

Seriously, do not have plan yet. Not interested in sleeving as it can cause its own thermal problems.

Trying to check if bore is "serviceable".

Thank you for making me laugh!

Mr .P
 

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Discussion Starter #12
Hi!
This is very similar to how my block looked after pouring 20L of fuel out when chainging oil...

I gotta go for injector failure leading to hydrolock, killing the rings and giving scaring.. And I think The 9cyl is The result of injector at cyl 8 spillning over doing same, but less damage to 9th cyl.
Hello Kickinit,

No #9 Cylinder issues, All back 2.

Hmmmm, When I received engine, the oil was not drained and I spilled a LOT when rotating on the engine stand (see pics under P-Chai). Too much oil, and thinking may be flooded with gas. This would support many comments on stuck fuel injector, but I, personally, have a hard time understanding how the engine could run and dump fuel to the extent of the damage to my block (cyl #8 and cly #10....same bank, different crank attachment points).

I have sent oil sample to Black Stone Lab's....waiting on results.

Mr. P
 

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Discussion Starter #13
Stupid spell check!

NO, as in not #9 cylinder issues.

Bank 2 is problem, not "back 2"

Grrrrr!
 

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lol, and I was thinking a tall end table!

Seriously, do not have plan yet. Not interested in sleeving as it can cause its own thermal problems.

Trying to check if bore is "serviceable".

Thank you for making me laugh!

Mr .P
It will hold 10 flower pots very nicely.
 

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Discussion Starter #17
Seems like broken ring land or piston led to the ring heavily scoring the walls in just a few areas. Could have been piston damage resulting from detonation localized in that part of the piston...Pure bore wash wear that I've seen looks a bit different, it doesn't go the whole way of the stroke and is more of a burnished area often some what inline with where excess fuel would accumulate. The location of the wear on 10 doesn't seem to be consistent with that failure mode at all.

Was that disclosed when you bought the block? Did the pictures show this in the auction? Not sure that the block can be salvaged unless a bore liner is installed but that may be more than what another undamaged block would cost.
Hello gmtegear,

Thank you for looking closely at the block condition and making informed comments.

When purchased engine was fully assembled and sold as "suspect rod bearings". I would like to believe seller did not know the bore condition and has actually been in contact.....a fellow M5er.

As for block, I still like end table vs flowerpot holder......

Have to laugh, or I'm going to cry :-(

PS: Do you know if the S85 bore is serviceable? It does not have liners from factory, but I seam to recall something about the BMW block material that could save me. Is it electro lined or bored raw?

Mr. P
 

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The block is made of Alusil which is a proprietary Aluminum alloy with high silicon content. It can be bored out but it requires some special processes and the surface finish of the machining has to be done to a very tight specification. it is not a lining or coating. There are not that many people who know how or have the experience to do this. I don't suppose it is cheap either. You then need properly sized pistons for the new bore diameter. I think you may be better off costwise with another used undamaged block, but I'm sure that's what you thought you were getting in the first place... Can you show is pictures of the pistons in those problem cylinders???
 

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Discussion Starter #20
The block is made of Alusil which is a proprietary Aluminum alloy with high silicon content. It can be bored out but it requires some special processes and the surface finish of the machining has to be done to a very tight specification. it is not a lining or coating. There are not that many people who know how or have the experience to do this. I don't suppose it is cheap either. You then need properly sized pistons for the new bore diameter. I think you may be better off costwise with another used undamaged block, but I'm sure that's what you thought you were getting in the first place... Can you show is pictures of the pistons in those problem cylinders???
Hello again gmtegear, and Thank You for the detailed response.

Your information matches what I "remember" about this block design from years ago. It is good to know it is serviceable, and I imagine pistons are available?

At this point, I rolled the dice again and ordered ANOTHER engine, assembled, with suspect bearings. It should arrive within a week. I will tear IT down and hope for the best!

THANK YOU again for your comments as they have been most helpful!

I hope that someday I may be able to answer a question for you, or at least forward the knowledge.

Mr. P
 

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