N62 Extreme Cylinder Wall Damage - Causes?

[BimmerBreaker]

Still looking for a 4.8, but not having any luck so far. Not super urgent either, the humidity this year has made working outside brutal. Normally I cool my garage with an evaporative cooler but those don't work when it's humid...

Originally Posted by Henn28

I recently had a discussion about bore scoring with a an Indy Porsche guy (his shop did a leak down and compression test on the m62 that came out of my x5). It’s very common on some model-year aluminum Porsche motors and their advice is to scrap the block unfortunately.

Generally speaking when an Alusil block is damaged it is time to scrap the block (and usually just replace the whole engine). Alusil blocks can be treated, if scratching is minimal, with the honing paste and felt pads. On my 4.4 I may experiment further, by first boring it via traditional methods, then going to a high grit paste, then the Alusil honing paste. I've read about some guys doing it themselves at home it this way (though never really seen a followup afterwards so idk if it works or not). I don't necessarily plan on running the engine after the work - I just want to see how it looks after for my own curiosity.

Originally Posted by EODguy

Has anyone contacted Melling in Iowa?
They used to be good helpful guys and were one of the go to places for sleeving...

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There are risks of sleeving, and the even more simple truth is for what a good N62 costs this level of machine work would never be financially justified.

Originally Posted by E30Dan

I have exactly the same wear on my N62B44 on No-8, I can see it from below when I had the sump off for a gasket change

I would say 99.9% this is due to overheating, mine has been overheated on at least 2 known occasions, the previous owner left it running on his drive and found out the electric cooling fan had given up, the tell tale sign was steam coming through the bonnet vents!!

I bought the car with several known faults, it has covered well over 50,000 miles since it developed piston slap because the bore/piston are so worn, it runs on 10W60 and hardly uses any oil, if I run it on 5W40 it smokes like crazy

Im sure ive read about your car on one of the facebook groups, im also doing a Z3 V8 but with an M62, do you have a more detailed write up on it? Would love to read more

It is very possible it's been overheated, it seems to be the thing most often suggested as the cause. It hasn't been overheated in my ownership, but it makes me think it happened for the previous owner and as it was still running he decided to sell it as-is...

I do have a very thorough, probably annoying thorough and overly wordy, build thread here: https://www.ascfabrics.com/z3v8
I've been meaning to distill the critical information down into a single post but haven't had time. The swap was a lot of work than I had envisioned at first. By the time I knew how much work it was going to be, I was already in too deep to back out

M62 swap is much, much easier though - they make swap kits for oil pan fitment and wiring harness adapters - if you gathered all the parts and had everything ready, you could do it in a weekend.