Old thread I know, but I wanted to point out a few things.
Even with the lead/copper bearings, oil analysis will not always pick up failing bearings, so you can't rely on that,
see here for my data on that.
DCT or manual makes no difference to a potential rod bearing failure.
Robbo
What did you buy in the end?
So you are saying every time one is sold then the bearings need to be changed
Of course you have only seen bad one. No one posts good ones. And many people post pictures of ones showing normal wear thinking they are knackered.
Generally people are getting them done for peace of mind at 50-60k. Anyone who knows what they are listening for will hear rod knock on a cold start anyway.
Oh and the ‘fix’ is people putting identical ones in. It’s more to do with many were ragged from cold in the early days and only being noticed now.
Almost no one posts good ones because almost none of them come out good, see
this thread with hundreds of photos of bearings pulled from different S65's, most of these people didn't know what they'd be like beforehand and changed them preventatively. So far I've gone through the 1st 48 pages categorising the bearings wear state, out of over 150 different engine's photos I've looked at, only 2 sets have normal wear!
I'll be going through the whole thread and categorising all decent photos, then I will post my list along with links to how bearings should look like with normal wear to the bearings (from any engine).
Btw, normal wear should barely be visible, wearing though the 1st layer, in say a lead/copper bearing, is not normal wear (unless the engine's done a
lot of mileage, perhaps 200k+), nor is wearing out the micro grooves in the later tin/alu bearings. When I say normal wear, I mean as detailed by Mahle(Clevite), ACL and King bearings.
Re rod knock, I thought that too originally, but after lots of reading around I found that by the time you hear rod knock, it's probably already too late. I've read through every single blown engine report in
this thread, (about 200), where people do hear rod knock (often they don't!) and have stopped ASAP, I only recall a few where the crank wasn't scored up by a spun bearing. (Gibbo was lucky as well as attentive).
And your way off about the fix (for most people it seems anyway), the (proper) fix is to put in bearings with greater clearance, as the std clearance by BMW (at the lower end of the tolerance range, especially for the older bearings) is
way too tight for the revs the engine can do and the oil they spec (as per recommendations by the
manufactures of the bearings, e.g Mahle, ACL, and King).
Sure, ragging it from cold will greatly accelerate wear, but when (if) you go through the rod bearing condition thread, see the photos, and see that most people state they did warm it up, and yet their bearings were in a rough state, are you saying they are nearly all lying??
Obviously we won't normally know what previous owners did, but it can't be just to some people not warming it up properly. Otherwise all high revving engines would regularly suffer such failures (e.g Google Honda S2000 rod bearing failures, and see how few hits their are).
Btw, I'm not claiming that all or nearly engines have failed, maybe it's only 1% of them?? (somehow I think more though). And some have gone well over a 100k miles without issues. But if they fail, the cost of failure is severe. Last time I looked a 2nd hand engine is about £8k (if you can find one), a new crank is ~£3k (if the block is ok), not to mention the huge amount of labour!
So yea, I agree with the statement you must change rod bearings (unless proven to have already been done of course
), not because it definitely will fail (good chance it won't), but because of the cost of it if it does fail vs getting rod bearings done. It's not scaremongering, it's very real.
When I eventually manage to get the bearings I want I will be changing them in my M3.
StonedPenguin
The US has far more M3's than we do, so in part at least that's why they have more problems.
Vita
Some people do exaggerate how often it happens, that's true, and yes people tend to only post bad news to forums, but bear in mind that many people who have taken their M3s to garages with failed engines won't post at all to forums. We have no idea of proportions of either camp of course. But this is where the rod bearing condition thread I linked above is a better source, most people their have had their bearings changed preventatively. If the problem was rare, then so would worn bearings be, sadly they're not.
Gibbo
Being under 75k is nowhere near a guarantee it'll be ok, sure it'll cut the odds somewhat, but plenty (enough) have failed under that mileage.
PS I avoided the DCT box as I didn't want the long term possibilities of problems (although they seem to reliable so far....), and avoided EDC because when the shocks fail, they are silly money! (but yea the EDC option is a better drive).