Engine rebuild after spun bearing

[JayDD007]

Figured I’d share the journey with everyone of my recent rebuild of an s63tu. I’ve replaced plenty of engines and performed countless valve stem seal replacements as a bmw tech but never a full rebuild including crankshaft replacement. Either way enjoy👍🏼

[JayDD007]

Being in the northeast we typically drop engines out the bottom with the subframe and transmission but rear wheel drive cars are almost easier to remove the transmission then pull out the top since the front suspension and steering can stay intact.

After engine removal the lower and upper oil pan were removed to asses the damage, that being cylinder 2 and 6 rod bearings both spun and seized the connecting rods to the crankshaft.

I’ve seen and heard of this before as most of you I’m sure have without much explanation. After all investigation of tearing down the engine I also unfortunately have no explanation of what or why caused this.

At 76k miles this engine is incredibly clean and has no evidence of failure whatsoever.

Oil starvation is the obvious culprit but reasoning is far from clear, so oil pump replacement was done for peace of mind.

[JayDD007]

Removal of the lower oil pan was first to inspect for any signs of debris, which none was found. In fact almost no metal was or shavings in the oil was present whatsoever which leads me to believe this wasn’t anything that could have been prevented.

I know this will scare some s63 owners as this is more common than it should be but within my research and being around these vehicles every day the only slightly logical explanation is allowing them to idle and warm up with the variable controlled oil pump slightly starves the bearings while the oil is cold and thick.

Regardless of this scenario or any other vehicle I always tell clients and friends to get oil to operating temp as quickly as possible. Obviously easy driving low rpm’s but the faster it gets to operating temp the happier it will be.

Everyone sees high mileage s63t’s with no issues. My assumption and only explanation is these vehicles are driven as they should be and they last for that reason.

Regardless the crankshaft and at least two connecting rods required replacement. In my mind the options were replace the crank, all eight rods and pistons with higher power components or go all oem and replace the crank and just two connecting rods.

Seeing as I had no intentions of doing any sort of high power build and all factory bmw parts come with a 2 year warranty I went the factory route.

[JayDD007]

Determining the crankshaft main bearings turned out to be quite a project between figuring out the code on the new crankshaft and the code engine block. Picture attached of the majority of the graph to calculate the bearing shell color.

Still blows my mind how that’s all figured out in Germany but all connecting rod shells are the same. Regardless plastiguage was used to ensure all clearances were perfect.

[cloverfield]

Really nice quality photos. I wonder if there's a way for BMWNA to compare data from dealers in one area of the country vs another to see if bearing failures are more common in places where the engines need to deal with far colder temps on a daily basis.

As you made reference to in your post, getting up to op temp as fast as possible is key. But how much longer does that take when it's 10F outside vs 70, and how much additional wear can that do over hundreds or thousands of cold starts?

[MarcF10]

Amazing post and photos. Thank you.
Regarding the oil, my suggestion is you only put 0-30W or 0-40W and avoid every other option

[JayDD007]

Originally Posted by cloverfield

Really nice quality photos. I wonder if there's a way for BMWNA to compare data from dealers in one area of the country vs another to see if bearing failures are more common in places where the engines need to deal with far colder temps on a daily basis.

As you made reference to in your post, getting up to op temp as fast as possible is key. But how much longer does that take when it's 10F outside vs 70, and how much additional wear can that do over hundreds or thousands of cold starts?

Very good point. This car actually lived most of its life in Texas, with only recently coming to the northeast.

Next few posts will be engine internals which were unbelievably clean at 76k miles, which also makes me even more curious about what the exact reason for failure was.

[JayDD007]

Tear down was relatively uneventful (which was good). Almost no metal was found in the oil which tells me the bearing(s) spun immediately without much sign of failure.

The crankshaft itself seemed to have gotten so hot it warped, thus it couldn’t make a full turn without binding every 180 degrees by hand. I have a video of this I can send anyone interested.

Which came first is tough to tell, whether the bearings spun first or the crank itself possibly got hot, warped and caused the bearings to spin.

Considering how the crankshaft oiling works you would think one of the end sets of rods would go first if it was an oiling issue, but after discussing this with multiple other techs in my shop it seems to be up to speculation.

[TTV8M]

Looking good

[JayDD007]

Installation of the bottom end was a time consuming job to say the least. After watching multiple videos of comparing plastigauge to all the typical engine building measuring tools, for my scenario I decided that would be satisfactory.

Speaking of satisfactory, seeing the new crankshaft spin freely in the block was about as “satisfactory” as it gets.

Then obviously the installation of all the rods and pistons, which was relatively simple because there was no colored bearing options for connecting rods.

In my experience I’ve never heard of any n/s63 having any sort oil consumption or compression issues due to piston rings so the pistons and rings were reused, obviously ensuring cylinder wall integrity.

[NEM5]

Did the owner describe the circumstances of the failure? Was the engine under load?

[JayDD007]

Originally Posted by NEM5

Did the owner describe the circumstances of the failure? Was the engine under load?

He said he was driving the car pretty hard, got a charging system malfunction and the car rolled to a stop in gear.

[TinCanSailor]

It is my understanding that the F90's oil pump is compatible with the F10 M5. I am curious to know if you have any details you can share about the improvements of the oil pump and if it could help with oil starvation.

[M5Rick]

So guys, the OP is saying that the variable controlled oil pump pumps more oil pressure with more revs so looks like the answer is to drive off with low revs after start up as it warms up the engine oil quicker.
The discoloured crankshaft bearings suggests to me an aggressive tune was once fitted in the past then removed and perhaps a skipped or delayed oil change did the rest.

[D4T]

Not sure if it's significant here or not but I recently watch a youtube video that had an M5 that'd basically been driven around a bodyshop for 18 months whilst it had extensive repair work done. Once finished the owner then noticed excessive oil consumption and poor running. The long and short of it was that fuel had contaminated the oil which was assumed to be caused by the rich running when cold and it never got up to proper temperatures.

I'm wondering if lots of these failures are somehow related? I.e. lots of short journeys which result in reduced oil quality which then goes on to lead to failures.

Or is my train of thinking flawed?

[M5Rick]

^ 18 months in a body shop is just crazy but not having an occasional long run in these and 'stop/starting all the time would have a slow detrimental effect on this type of engine.

[D4T]

Well mine takes a long time to warm up, so im thinking cars that do short school runs etc. might be the ones that ultimately died... just a long shot theory!

[M5Rick]

Originally Posted by D4T

Well mine takes a long time to warm up, so im thinking cars that do short school runs etc. might be the ones that ultimately died... just a long shot theory!

The long warm up is normal unless you live in a hot climate, 9.5 litres of oil is a huge amount of oil to get around.

[D4T]

Yeah I appreciate it’s normal, just wonder if people who’ve experienced failures are typically doing many shorter journeys then the rest of us

[M5Rick]

I think it's not necessarily short journeys, more likely using full power before being fully warmed up and leased cars from earlier life getting abused by careless drivers before handing them back for newer ones. There's also a factor some don't want to know, I always use BMW service and very happy with the service which I wouldn't be sure handing the car to an indy, I won't say more on that.

[D4T]

Yeah I agree but i have seen reports like "my wife drives it and this happened" etc so i do wonder if there's some other aspect coming in to play

[D4T]

I’m lucky, mines too scared to drive mine! Not because it’s quick but because of how grumpy I’d be if anything happened to it