Another Rod Bearing Story

[R60BBA]

Bearings can last 200,000+ miles as long as the car is looked after (ie regular oil changes and the car is warmed up properly).

While this is true for a "normal" engine such as an M54, it's shouldn't be a blanket statement, especially for the S54. Mine has had it's oil changed regularly (every 3k-5k miles) and don't go past 4k rpm until car is properly warmed up. However, my oil analysis showed 15ppm average lead level since I started doing analysis at around 22k miles. Lead level dropped to less than 2ppm after bearings changed at about 55k miles. This steer me to believe that my bearings weren't properly installed (torqued) from day 1 at the factory. My car was built on March 2008, which I thought should be the latest and greatest iteration. I was obviously mistaken for making that assumption. I suspect many later S54 are the same, which is why I have seen worst bearing wears on S54 Z4M than those final E46 M3.

Even with the high average of 15ppm lead wear, the bearings made it to 55k and probably could have done another 10k miles, I'm fairly confident that the current set of bearings could make it to the next 100k easily with only 2ppm of lead wear...so my next change should be right around 150k.

You should keep it under 3,000rpm mate.

Perhaps misassembly at the factory also comes into it, but surely if that was the case then they would have spun early on into ownership.

And not sure about that either mate. Rod bearings can fail on all types of engines, not just high performance engines. I saw a tatty Ford Transit Van develop rod knock about year or so ago outside my house…Nevertheless the principles remain the same regardless of performance, look after it and it will look after you.

[GuidoK]

Yet some engines develop way more problems than others. For instance, compare the m54. That is an engine that is probably made in numbers 50 times as much as the s54.
Ever heard of one of them throwing a rodbearing? Or having worn bearings? Ever seen one? M54's are driven till silly high mileages.
So either the owners of those engines are way more good to them (which is highly unlikely as M cars get constant pampering of their owners in the garage and the m54 is a workhorse daily drive engine) or there is a wearissue with s54 rodbearings.

If all things were the same you'd hear m54 engines throwing rodbearings constantly with the amount they're produced compared to the s54.

[NLW73]

Does the m54 rev as high as the s54? Anything over 8k rpm is going to put a lot more load than say at 7.5k

God knows how Porsche give a warranty with the 9k rpm 4 litre gt engine. Very exotic parts and a £50 k price tag for an engine

[GuidoK]

Does the m54 rev as high as the s54?

No

Anything over 8k rpm is going to put a lot more load than say at 7.5k

Exactly.
But it's not just the revs. Its also the lenght of the stroke. The weight of pistons and conrods. But also the shape and lenght of the oil passages. The stability of the oil pressure, the play in the bearings etc etc etc.

God knows how Porsche give a warranty with the 9k rpm 4 litre gt engine. Very exotic parts and a £50 k price tag for an engine

totally different design. For starters it's an oversquare engine. For the rest: see above for some of the parameters
But that is a great engine too. However, somewhere that engine also has a weak point. Every engine has. What's important is how expensive it is to deal with those weak points, and porsche has had it's fair share of very very expensive weak points in it's engines
I mean the m54 also has it's weak points, but they are fairly easy to correct. Disa valve (about £250 or buy a metal repair kit for £75), vanos (ring set incl seals etc: £75). Luckily all fairly cheap. And these are fixes you can do on your driveway.

[XMetal]

You should keep it under 3,000rpm mate.

Perhaps misassembly at the factory also comes into it, but surely if that was the case then they would have spun early on into ownership.

And not sure about that either mate. Rod bearings can fail on all types of engines, not just high performance engines. I saw a tatty Ford Transit Van develop rod knock about year or so ago outside my house…Nevertheless the principles remain the same regardless of performance, look after it and it will look after you.

So how do you explain how my original bearings are wearing 8x as much as my replacement bearings on the same car, same driver, same service intervals, and similar driving condition?

[GuidoK]

So how do you explain how my original bearings are wearing 8x as much as my replacement bearings on the same car,

Do you have pictures of both worn sets?

[R60BBA]

Yet some engines develop way more problems than others. For instance, compare the m54. That is an engine that is probably made in numbers 50 times as much as the s54.
Ever heard of one of them throwing a rodbearing? Or having worn bearings? Ever seen one? M54's are driven till silly high mileages.
So either the owners of those engines are way more good to them (which is highly unlikely as M cars get constant pampering of their owners in the garage and the m54 is a workhorse daily drive engine) or there is a wearissue with s54 rodbearings.

If all things were the same you'd hear m54 engines throwing rodbearings constantly with the amount they're produced compared to the s54.

https://www.bimmerfest.com/threads/m54- ... es.799745/

You were saying…

[R60BBA]

You should keep it under 3,000rpm mate.

Perhaps misassembly at the factory also comes into it, but surely if that was the case then they would have spun early on into ownership.

And not sure about that either mate. Rod bearings can fail on all types of engines, not just high performance engines. I saw a tatty Ford Transit Van develop rod knock about year or so ago outside my house…Nevertheless the principles remain the same regardless of performance, look after it and it will look after you.

So how do you explain how my original bearings are wearing 8x as much as my replacement bearings on the same car, same driver, same service intervals, and similar driving condition?

You can’t establish wear without removing the shells.

Oil samples should be taken with a pinch of salt.

[GuidoK]

https://www.bimmerfest.com/threads/m54- ... es.799745/

You were saying…

That's an engine with additional damage. It's not a rodbearing problem. The rodbearings are a result of that.
Oil pump/feed failure, headgasket failure. Thus extreme overheating.
These are not worn rodbearings, these are damaged. There's a difference.

And yet not bad for an engine that is produced in at least 50 times the numbers if you can only come up with this example that is not really applicable. I would have expected dozens and dozens of examples if you were right. (like you can find dozens and dozens of examples of flappy disa valves and ratteling/replaced vanos rings on m54's)

Obviously somewhere out there, there must be an m54 with worn rodbearings/rodbearing failure, but probably with ridiculous mileage or an abused engine. But just not in the amount of the s54, and that is an engine that was made in much much smaller production numbers.
So the cases just can't really be compared.

[Argenta]

Coming from mostly italian cars, rod or main bearing issues are unheard of generally. Most Fiat bearings are double size! (My Coupe (turbo1998cc 5cyl 340hp) was as heathly as ever at 200k miles). I suppose Bmw took a risk at really minimizing friction.

[XMetal]

You can’t establish wear without removing the shells.

Oil samples should be taken with a pinch of salt.

Well, my oil samples analysis definitely didn't lie. Have a look here => https://www.zpost.com/forums/showthread ... l+analysis

[R60BBA]

You can’t establish wear without removing the shells.

Oil samples should be taken with a pinch of salt.

Well, my oil samples analysis definitely didn't lie. Have a look here => https://www.zpost.com/forums/showthread ... l+analysis

You said your current bearings are wearing 8x less than your original bearings.

Unless you take out your replacement bearings and visually check there is no way you can make such a statement.

[NLW73]

[/quote]
totally different design. For starters it's an oversquare engine. For the rest: see above for some of the parameters
But that is a great engine too. However, somewhere that engine also has a weak point. Every engine has. What's important is how expensive it is to deal with those weak points, and porsche has had it's fair share of very very expensive weak points in it's engines
I mean the m54 also has it's weak points, but they are fairly easy to correct. Disa valve (about £250 or buy a metal repair kit for £75), vanos (ring set incl seals etc: £75). Luckily all fairly cheap. And these are fixes you can do on your driveway.
[/quote]

very true. if you look at the M96 and M97 engines in the 996.2 and 997.1 3.6 and 3.8 engines they seem to have issues with bore scoring. seems to happen on the cylinder 6 where its furthest away from the oil cooling and where the oil moves around

they changed the design for the 997.2 DFI engine (direct injection) but now some are having issues with coked up engines which puts pressure on the internals and piston rings!! companies that get run by accountants not engineers seem to have these issues.

the mezger engines in the GT3's up to 997.2 have titanium con roads and a very different head and oil feed system as dry dumped so lateral loads don't impact. an amazing design but the engines are 40k a pop

the 991.1 GT3 engine which revved to 9k had issues with cam followers and mate of mine had 4 engines from Porsche until the G series engine came out. they seem to have sorted it out with the 4 litre Gen 2 engines but that's a motorsport lump and probably 40-50k worth of parts and cost to repair!!!

[mmm-five]

I used to do oil analysis on the e34 M5 (every 3 months at the mileage I was driving)...but they never warned of anything catastrophic, and didn't foresee the stuck valve that killed Cyl1.

Now, I never bothered with oil analysis on the Z4 - I just carefully look at the oil I drain every 5-6k miles and see what I can see.

It was fine...until it wasn't...but that was at 160k miles, so I don't feel too bad

[XMetal]

You said your current bearings are wearing 8x less than your original bearings.

Unless you take out your replacement bearings and visually check there is no way you can make such a statement.

This is true and it is the exact issue that I have your blanket statement saying bearing wears are not much an issue for the S54. The fact of the matter is that you don't know unless you had taken out everyone's bearings and visually inspect it. I would rather err on the side cautious than wait for it to go bang.