S54 rod bearing
- Thread starter Vanne
- Start date
They are into it in the USA.... Not so much in the UK i guess although i think its getting more popular...
If you are thinking of tracking the car at any point i would be putting my hand in my pocket,the bearing shells are relatively easy and cost effective for peace of mind.... If they spin and do a rod and the crank,then the price will escalate rapidly..
If you are thinking of tracking the car at any point i would be putting my hand in my pocket,the bearing shells are relatively easy and cost effective for peace of mind.... If they spin and do a rod and the crank,then the price will escalate rapidly..
To be honest I'm quite surprised your shop didn't look at the bottom end whilst it was apart as this is where the worn parts of your cams and followers may have ended up. Admittedly it would have been an extra expense but for piece of mind I would have thought they would have offered you the option.
Get the rod bolts changed for ARP uprated bolts if you do do the work.
http://www.part-box.com/bmw-e36e46-rod-bolt-kit-p-6310.html
Get the rod bolts changed for ARP uprated bolts if you do do the work.
http://www.part-box.com/bmw-e36e46-rod-bolt-kit-p-6310.html
TomK said:
Yea what happened was they were going to do the bottom end as well whilst it was in having the cams done. But they had someone go off sick so I agreed to just get the top end finished and book it back in for the shells. But then I was waiting for the brakes before I booked the combined job. So once the front calipres are back she is going in!
exdos said:
Have you seen spun bearings/broken conrod bolts on engines where the other bearings were all in good nick?
It would be a hell of a conincidence if a con rod bolt breaks, and the bearings have wear and those two are not related.
The bang you hear is the bearing seizing probably, breaking of the locating tabs etc.
There are lots of examples that bearings have spun on s50/s54 and that the bolts havent broken or fallen out but are still firm in place. So on these examples the conrod bolts are definately not the culprit.
GuidoK said:
I’ve been following this issue with The S54 from the early days and I don’t think the problem was as straightforward to solve as you suggest and BMW has never actually given any detail of the problem or the solution, so we’ve been left to do our own analysis based on the various “fixes” that BMW has put in place to rectify the problem.
You can read a decent chronology of the problem here: http://www.zpost.com/forums/showthread.php?t=962807
Some of the earliest failures were seen as thrown rods rather than preceded by the knocking of bearing shell failure.
BMW issued Technical Campaigns
Status Defect Code SI Defect Description Done
0011940100
In which it states: “Contrary to the specifications of all other BMW engines, the connecting rod bolts should not be replaced. The
connecting rod bolt must only be reused in the same thread. If a connecting rod or a connecting rod bolt with
tread M11xM1.25 is damaged, the connecting rod must be replaced with a complete set of rod and M10x1.25
connecting rod bolt.
Engine S54 with M10x1.25 connecting rod bolt: The connecting rod bolts must be replaced.”
BMW then discontnued the original con rods and bolts and replaced them with revised parts. In comparison, the S50 B32 (with similar performance) has always used the original con rod and con rod bolts which are still available today. Why did BMW come up with different spec con rods and con rod bolts just for the S54? Why has the incidence of catastrophic engine failure now been considerably reduced since these revised parts are fitted to later S54 engines?
Here’s a webpage which gives a reason for using ARP con rod bolts rather than OEM: http://bmwspecialistreading.co.uk/e46-m3-spinning-con-rod-bearings/ It clearly states that stretched con rod bolts allow the bearing shells to spin and creating an oval in the con rod around the crank. Bearing shells are supposed to be specifically designed to have the correct amount of "crush" which should prevent them from spinning, whilst having the correct clearance around the crankshaft for lubrication.
From my own experience of bearing shell failure, I didn't hear a single "bang", instead I heard a repetitive loud knocking, like a Kango Hammer in use. The damaged bearing shell was hammered into a very thin shell inside the con rod giving huge clearance around the crankshaft.
It seems we are discussing which came first, the chicken or the egg? The problem of catastrophic failure seen in many of the early S54 engines has now been largely resolved, and the later S54 engines in the Z4MR/MC do not have the same high failure rate. However, it seems that when most S54 engines are examined the incidence of wear/cavitation of the bearing shells is still very high. So why is the incidence of BS wear still high yet catastrophic bearing shell failure now relatively low? Where's the correlation?
That is typical of a rodbearing with play. (either spun or just play caused by lack of lubrication etc)exdos said:
Still I think the S54 with the m10 conrod bolts still fail often if not cared for with new bearing shells.
I mean if it was only the rodbolts, there would be no need for changing the shells.
This problem is very old, much much older than the s54 thread on zpost.
Look at S50 history and how they failed. Always bearing shells.
(look at european sources for that, US fora have nothing as they didn't get the eurospec s50)
I certainly wouldn't leave the half worn bearings in place and swap only rodbolts to arp or whatever brand and suspect that solves the problem.
Where I live swapping out bearings at 60k miles is general practice by most shops that specialize in s50/s54 engines since even before the s54 era as it is like I said an age old problem (early/mid 90's) and with that treatment engine fails is completely eliminated. So they must do something right no?
Also the amount of crush on bearings does not prevent them from spinning. The small retaining taps do that. In fact the bearings should not have crush at all, they should have a minute amount of play to allow an oil film. That amount of play you check, measure and adjust with plastigauge and shells in different diameters.
If you look at your link, all those taps have broken off. That is the result of too much friction on the bearing, not the stretchin of the bolt. The conclusion of that site is totally wrong.
Spun bearings are caused by too much friction on the bearings. Always caused by some lack of lubrication, which can be oil starvation or no proper oil film due to uneven wear, wrong oil etc etc. But bolts stretching is not very likely, as they would exceed their elasticity and loose their torque. And that does not happen, the sign of that is that they would rattle out (I've heard of an alfa engine though where that happened....)
At least that's my view, but that that site doesn't mention the broken off tabs is to me a clear sign that they have no idea what they're playing with or that they really like to sell a set of ARP bolts... which one is it... :scratchhead: :lol:
Who knows why bmw switched to m10 bolts. It could even be price. parts are swapped and revised literally all the time. No need to fill up the old stock with m11 bolts, just let the customers buy a complete set of new rods etc. BMW win-win :lol:
But hey, you do to your engine what you think it's best
Liverpool
I wonder if the reason I've not had this problem*, is that I had a new engine in 2009? That would mean it would have had the latest & greatest tweaks before production finished
...or maybe I'm just lucky/oblivious
* just you watch me now go and have a failure at the 'Ring this weekend
...or maybe I'm just lucky/oblivious
* just you watch me now go and have a failure at the 'Ring this weekend
mmm-five said:I wonder if the reason I've not had this problem*, is that I had a new engine in 2009? That would mean it would have had the latest & greatest tweaks before production finished
...or maybe I'm just lucky/oblivious
* just you watch me now go and have a failure at the 'Ring this weekend
How many miles on your new engine?
How come it had to have a new unit at a few years old ??
121,000 - but that's with lots of oil changes (i.e. on top of the schedule ones, there's one after a track day and one every 7,000 miles)Z4M-2006 said:
Engine replaced under warranty after they couldn't diagnose lumpy running (ran on 5 cylinders no matter how you swapped the plugs/leads/coils around). The dealer finally settled on 'a VANOS issue' (which we don't think it was as that was one of the first tests they did) and asked BMW to replace it as the labour cost for diagnosis was getting close to £5k.Z4M-2006 said:
GuidoK said:
Neither would I. I think it's obvious to all of us that worn bearing shells is not ideal, so if you happen to be down in the bottom of your S54 engine then it would be very sound practice to fit new bearing shells when rebuilding.
My engine went kaput at 31k miles so even on a general replacement policy at 60k miles, I, and many others like me, were not protected! So how can anyone predict catastrophic failure? I'm not convinced that oil analysis is the answer.
That's not what I've read.GuidoK said:
GuidoK said:
The S54 engine has one of the highest piston speeds of any production car at 4773.33 Ft/min, and with one of the largest strokes, which combined, means that the bearing shells are under tremendous force and so with an engine of this type, I suppose bearing shell wear is to be expected and replacement factored into the maintenance schedule.
I've seen photos of an S54 engine in which the bearing shells in all 6 cylinders had spun, yet the engine ran sound. So spun bearings don't always produce instant disaster and catastrophic engine failure.
I'm just trying to understand what is the straw that breaks the camel's back and I accept that it's not always the same straw.
You know what plastigauge is and how it works? Have you ever used that?exdos said:
If there was crush on the bearings, it wouldn't work.
Hence no crush..
Wait what?!?!?
You've seen spun bearing and the engine ran sound as usual? Like nothing happened?
Sorry, but I don't believe that.
I'm not saying that spun bearings always result in disasters like broken pistonrods etc , and that the engine can't run anymore, but if you have spun bearings your engine doesnt run anything like 'nothing has happened'. You hear all kinds of tappety noises as all tolerances are gone, completely gone...
Of course you can't predict failure with oil analysis. It doesn't say anything about where the wear is coming from and in wat form etc etc.exdos said:
You can only say that if you see raised amounts of lead, copper or other bearing related materials in the oil higher than usual, the design and use of the engine is critical on some bearing somewhere. Thats it.
If you want to see the state of any bearing, you have to get your hands dirty obviously...
The people who think that an oil analysis has such a specific meaning, are generally not the people who get their hands dirty :lol:
I'm not an engine builder but I do know of plastigauge and its use. Are you an engine builder?GuidoK said:
Here's a link to something about "insufficient crush": http://www.nb-cofrisa.com/docs/web_fallos_ing.pdf why is that wrong?
GuidoK said:
IIRC the photos and information were from Randy Forbes (well respected in Z3 M circles in the US who does a lot of BS replacements).
I'm not an engine builder, but I sometimes do repair bearing components on tolerance issues when the factory stuff doesn't meet it's specs anymore. But on far larger bearings (ships, industrial compressors etc, where money is less of a subject, as these type of repairs take much time and thus cost more money than someone would ever put into a car).
They use the word crush as a fitment intolerance. but that is not something that is obtained by the con rod bolts. The torque on that is far far to high to provide tension on the bearings. That torque is there to assure that the bolt doesnt come loose/breaks. There is also no room for the conrod bolts to provide any tolerance in that. Especially on bmw pistonrods, the fitment is absolute (they have a broken bigend instead of machined, so something like shimming is also not possible)
Only if your torque is way off and the bolts sits loosely in its hole, you have 'insufficient crush', but that is how far the influence of the bolt goes imho and that is a mechanics error.
The fitment should be snug. that's also how you can interpret crush.
If the bearings where really tightened by the torque of the conrod bolts, there would be no space for the oilfilm. That's why you plastigauge your bearings if you suspect there might be a fitment issue (for instance after an engine overhaul or service). And that's how you decide you go over/undersize etc.
As for randy forbes, never heard of him and havent heard his specific spun bearing engines he had lying around. Also haven't measured his hearing ability for that matter, so I have nothing relevant on that.
They use the word crush as a fitment intolerance. but that is not something that is obtained by the con rod bolts. The torque on that is far far to high to provide tension on the bearings. That torque is there to assure that the bolt doesnt come loose/breaks. There is also no room for the conrod bolts to provide any tolerance in that. Especially on bmw pistonrods, the fitment is absolute (they have a broken bigend instead of machined, so something like shimming is also not possible)
Only if your torque is way off and the bolts sits loosely in its hole, you have 'insufficient crush', but that is how far the influence of the bolt goes imho and that is a mechanics error.
The fitment should be snug. that's also how you can interpret crush.
If the bearings where really tightened by the torque of the conrod bolts, there would be no space for the oilfilm. That's why you plastigauge your bearings if you suspect there might be a fitment issue (for instance after an engine overhaul or service). And that's how you decide you go over/undersize etc.
As for randy forbes, never heard of him and havent heard his specific spun bearing engines he had lying around. Also haven't measured his hearing ability for that matter, so I have nothing relevant on that.
Here ya' go
I've just looked for the posting where I saw the photos (back in October 2010). I'd posted photos of my damaged bearing shell and Randy Forbes posted this:
"John, can I use that picture of your #5 bearing shell?
Besides the trunkfloor/differential mount work I do, I've also been replacing the rod bearings in the 01-02 M Coupes/Rdstrs using the M3 bearing recall kit. I've probably done a dozen or so cars in the past year.
As the cars I work on have not yet failed, what I find are the bearing inserts have partially rotated in their bores, certainly the first step towards a "spun bearing" as we call them on this side of the pond.
Only a couple of the cars have NOT exhibited this condition, thankful that one (1) of them was mine! I've also seen some errosion, and that concerns me too.
Note: my server is being moved this weekend, so these pictures may not be visible immmediately, but do check back..."
Unfortunately the 11 photos in Randy's posting are no longer linked to his posting but the explanatory texts states what photos he posted for the world to see. So sorry you don't believe me.
I've just looked for the posting where I saw the photos (back in October 2010). I'd posted photos of my damaged bearing shell and Randy Forbes posted this:
"John, can I use that picture of your #5 bearing shell?
Besides the trunkfloor/differential mount work I do, I've also been replacing the rod bearings in the 01-02 M Coupes/Rdstrs using the M3 bearing recall kit. I've probably done a dozen or so cars in the past year.
As the cars I work on have not yet failed, what I find are the bearing inserts have partially rotated in their bores, certainly the first step towards a "spun bearing" as we call them on this side of the pond.
Only a couple of the cars have NOT exhibited this condition, thankful that one (1) of them was mine! I've also seen some errosion, and that concerns me too.
Note: my server is being moved this weekend, so these pictures may not be visible immmediately, but do check back..."
Unfortunately the 11 photos in Randy's posting are no longer linked to his posting but the explanatory texts states what photos he posted for the world to see. So sorry you don't believe me.