Z3M S50 Conrod bolts stretched and big end knock

[Desiro]

I will start with a little history

The car has covered 37K.

The last 300 hundred miles of my trip to Europe was done with a tip blown off number 5 plug, so as you can imagine it ran a bit rough. The plugs were replaced as part of an inspection II and all ok.

Shortly afterwards a very slight misfire developed at around 1300 rpm under very light load. 3 coil packs and a throttle position sensor later and it was still the same.

Now here is the bad part.

I noticed a rattle from the engine when I put it in the garage one night, but no lights on the dash and the oil level is ok. The noise can be heard on tick over and increases with engine revs.

I contacted my local indy Quarry motors who had done the previous work and they recommended hauling it down to their workshop for diagnosis. There are no faults logged.

As far as I am aware they have only listened to it but are saying the conrod bolts have stretched and the shells have spun.

£3000 quoted to rebuild the engine.

There are no engines available with such low mileage.

Thoughts gentlemen please.

[shantybeater]

Definately get a second opinion. A missfire and rattle could be a alot of different things...How prominent is the rattle? do you have any vids/sound clips?

[Desiro]

Definately get a second opinion. A missfire and rattle could be a alot of different things...How prominent is the rattle? do you have any vids/sound clips?

I will try to borrow a something to record the sound when I get back to work next week.

They will not start work on the car until I give the go ahead.

[hornel Z3M]

hi Desiro. Sorry to hear about your problem. can you say why you drove 300 miles with a blown tip off the plug, or did you not know then?

[Desiro]

hi Desiro. Sorry to hear about your problem. can you say why you drove 300 miles with a blown tip off the plug, or did you not know then?

Hi Hornel I was in Germany on a sunday when it started to miss fire and had no idea what the problem could be. I drove it slowly back to Rotterdam and then home from Hull.

I still do not think the plug is related to the problem i have now because apart from the slight missfire it was running ok with no decrease in power.

I have arranged for a second opinion this evening, which is good because I have not got a clue.

[myredzed]

Just a thought - I don't suppose the rattle you can hear could be the tip of the blown spark plug rattling around at the top of the cylinder could it?

[Deano1712]

I can't see how they can come to that conclusion from what you have stated. I wouldn't let them do anything to the car.

I can't see how a conrod bolt can 'stretch'. More likely they would fail and you would have catestrophic engine failure. You would only get a problem with the rods if the engine had been over-revved. Do you think it ever has been?

Running the engine with a broken plug may have caused some damage. The cylinder would have been running with unburnt fuel passing through it and that may have diluted cylinder wall lubrication. Its more likely you have a worn piston ring, than a conrod problem. Ring failure would be picked up easily with a compression test. Have they done that?

If you are faced with an engine rebuild my advice is that it wold be cheaper to source another S50 engine than rebuild the one you have. I see you have low mileage but I would think a secondhand 60k mile engine for £1k is more agreable than a £3k rebuild to your existing engine.

Sorry for your bad luck!

[6 pot roadster]

Hi, let me first comiserate you on your misfortune. I've killed a few engines my self in my time.

Streched big end caps are normally quiet at idle as there's no real force involved. if they were that worn they knocked at idle then IMO they would be visable through the side of the block if you revved the engine under load. *BANG*

conrod bolts would 'normally' only strech if you had buzzed the engine. ie briefly over revved the engine by say down changing quickly and mechanically passing the rev limiter

I agree with Deano "Running the engine with a broken plug may have caused some damage. The cylinder would have been running with unburnt fuel passing through it and that may have diluted cylinder wall lubrication. Its more likely you have a worn piston ring, than a conrod problem."

Get a long metal bar and use it as a listening stick, holding one end to the engine block as close to each bearing as you can actually hear the bearing (it also works for camshaft lobes and water pumps) a healthy bearing should just sound like an engineering whirring noise and a worn one will of course 'clack'.

[TitanTim]

Really sorry to hear this

I'm guessing if the tip has blown on a spark plug then its dropped into the engine. I know this was a problem on the Corsa VXRs due to the piston running hot and melting the spark plug tip resulting it being passed through the engine and damaging the turbo.

Agree with Deano and second hand engine if you can find one might be the best way forward and possibly cheaper.

Whatever has caused the problem, hope you get it sorted soon.

Tim.

[RemarkLima]

Also, surely if it's the shells then it's not a massive job to pull the sump and take a look before going for the whole rebuild?

['Yadi]

I can't see how a conrod bolt can 'stretch'. More likely they would fail and you would have catestrophic engine failure. You would only get a problem with the rods if the engine had been over-revved. Do you think it ever has been?

IIRC wasn't this was the debate the S54 engined coupe owners had with the whole conn rod bearing shell issue? Crucially BMW and some mechanics quoting the advisories reusing the original bolts when the shells were changed (as per the E46 M3 recall) vs mechanics and engineering type owners advising on swapping out the bolts with stronger ARP ones because they believed it was the stretching of the poor original bolt that gave scope for the spinning of the shell rather than the material makeup of the shell itself.

Most (understandably) argued they'd not over-revved at any point.

Not suggesting that this one has been or I've superior technical knowledge. Just been researching the problem and wisdom in taking preventitive measures on mine recently.

Documented on an S50 MC too
http://www.z3mcoupe.com/forum/showthread.php?t=3388.
http://bmwcarmagazine.com/forums/thread ... adID=63953

[offyourmarks]

Nothing technical to offer I'm afraid.

I am just very sorry to read your story. Its a shame such an epic road trip has ended with this problem.

Hope you get it sorted

[Desiro]

I should have taken more notice when when they told me about the plug, but of course I did not know what was to come.
If it was the centre electrode which had burnt away gradually over time then I dont think that would have caused a problem. If it was the side electrode and it had fallen into the cylinder then I assume damage will occur.

I did smell fuel while I was driving home from Germany so maybe the cylinder wall is damaged. I will pass this info on when I get the second opinion.
regarding over reving, it's only hit the rev limiter once, maybe twice when I was a little over zealous.

After I've had the second opinion I can decide on a way forward, fortunately I dont need to use it every day.

I'm off to read the coupe threads from yadi.

thanks for the help

[siwilson]

I can't see how they can tell the shells have spun without looking at them.

All the best with your second opinion.

[Deano1712]

REALOEM shows an anti-rotation feature so it looks like its impossible for the shell to rotate anyway!

http://www.realoem.com/bmw/showparts.do?model=CK92&mospid=48084&btnr=11_1317&hg=11&fg=20

[siwilson]

REALOEM shows an anti-rotation feature so it looks like its impossible for the shell to rotate anyway!

http://www.realoem.com/bmw/showparts.do?model=CK92&mospid=48084&btnr=11_1317&hg=11&fg=20

Yes. the locating tang. They shouldn't, but nevertheless some do. A Few of those that did a preventive replacement on S54s have reported some rotation on one or twp shells, but had no symptoms at all beforehand. If you scan through Randy Forbes images on Bimmerfest you can see some.

I guess S50s are not immune to this, but I can't recall hearing it as an issue before. I am skeptical that even a mechanical (money shift) over rev would cause this. far more likely to see valve damage first.

It might be worth having an endoscope put down the plug hole of the cylinder that had the bad plug to see if there is any damage. The electrode could have damaged the piston, valve or bore, but equally could have been shot directly out the exhaust port.

Crossed fingers for you.

[Desiro]

I can borrow an endoscope from work, but not until next week so I can have a look down the plug holes for damage.

I supose i could look up through the sump via the sump plug too. not sure Quarry motors would let me do that on thier premises though.

do you think there is any merit in having an oil sample analyzed, we use a company at work called scientific services who do gearbox oil sampling for us.

Thanks for your continued support.

['Yadi]

I purchased the S54 M3 recall kit and saw the tangs on the shells - I'd assumed the shells when they 'span' rotated solely within the circle of the conn-rod parts that enclosed them so couldn't figure out how when I saw the tangs

Most pictures of wear seem to show evidence on the inside of the shells like scratching and I guess small particles get into the oil and cause the problems....
Then I saw pics like this (an S50) and realised they can rotate on another axis....
http://forums.bimmerforums.com/forum/sh ... stcount=19

Common theme seems to be Cylinder No.5 as a weak point - interestingly quite a few seem to report that it happens very shortly after a scheduled oil change but I get the impression a lot of US owners change the oil on the lunar cycle.

Another S50 MC owner for more reference - andrewturner -
http://www.z3mcoupe.com/forum/showthread.php?t=9388

and someone checking their engine out for wear with pics
http://m3forum.net/m3forum/showthread.php?p=1065047190

OP - hopefully these links will give you more reference for what the mechanic will be talking about. (Mine's in next week to have the M3 recall kit installed)

Hope it all gets sorted as agreeably as possible for you.

[siwilson]

I can borrow an endoscope from work, but not until next week so I can have a look down the plug holes for damage.

I supose i could look up through the sump via the sump plug too. not sure Quarry motors would let me do that on thier premises though.

do you think there is any merit in having an oil sample analyzed, we use a company at work called scientific services who do gearbox oil sampling for us.

Thanks for your continued support.

I am not sure an oil sample will tell you much at this stage since you do not have any previous reading to compare with. Oil samples work best when done over time and a trend can be seen. I suppose if the copper or lead was off the chart it may confirm what you have been told.

[Desiro]

I am not sure an oil sample will tell you much at this stage since you do not have any previous reading to compare with. Oil samples work best when done over time and a trend can be seen. I suppose if the copper or lead was off the chart it may confirm what you have been told.

I was thinking exactly that Si but thought I would throw it in the mix to see what others thought.
If I can get the sample done for free then I may as well go ahead toconfirm the bad news.

[offyourmarks]

Have Quarry motors divulged how they came to their diagnosis?

They seem to have a good reputation normally

[exdos]

I'm sorry to hear your trouble. I had a catastrophic bearing shell failure on my S54 MC 2 years ago and the noise sounds like those "clackers" toys (as seen in the 1970s) when it starts and is obviously related to the revs.

I've also witnessed a spark-plug failure on another S50 MC and heard of a few other spark-plug failures too. If you've been lucky, the bit's will have blown out of the cylinder and they'll be safely trapped in front of the cat. You can check the affected cylinder and piston for damage with an endoscope and also see if the bits from the spark plug have exited the cylinder. A compression test is easy to do and will show if the affected cylinder has lost compression by comparison to the other cylinders.

If you can eliminate damage from the cylinder, then get the car up in the air and follow 6 pot Roadsters advice of "Get a long metal bar and use it as a listening stick, holding one end to the engine block as close to each bearing as you can actually hear the bearing (it also works for camshaft lobes and water pumps) a healthy bearing should just sound like an engineering whirring noise and a worn one will of course 'clack'." If you then need to investigate further, drop the sump and take a look at the bearing shells, with the view to preventive replacement if you find them to be OK, but if they're damaged then you need to assess the state of the crankshaft etc. and you can work out your options of repair or replacement.

[Desiro]

Have Quarry motors divulged how they came to their diagnosis?

They seem to have a good reputation normally

I have nothing against Quarry motors, they have treat me well in the past and geniunely believe they are confident with thier diagnosis.

It is not thier £3k if they get it wrong though.
The car is comming home this weekend so I can do a few checks myself.

[Desiro]

I'm sorry to hear your trouble. I had a catastrophic bearing shell failure on my S54 MC 2 years ago and the noise sounds like those "clackers" toys (as seen in the 1970s) when it starts and is obviously related to the revs.

I've also witnessed a spark-plug failure on another S50 MC and heard of a few other spark-plug failures too. If you've been lucky, the bit's will have blown out of the cylinder and they'll be safely trapped in front of the cat. You can check the affected cylinder and piston for damage with an endoscope and also see if the bits from the spark plug have exited the cylinder. A compression test is easy to do and will show if the affected cylinder has lost compression by comparison to the other cylinders.

If you can eliminate damage from the cylinder, then get the car up in the air and follow 6 pot Roadsters advice of "Get a long metal bar and use it as a listening stick, holding one end to the engine block as close to each bearing as you can actually hear the bearing (it also works for camshaft lobes and water pumps) a healthy bearing should just sound like an engineering whirring noise and a worn one will of course 'clack'." If you then need to investigate further, drop the sump and take a look at the bearing shells, with the view to preventive replacement if you find them to be OK, but if they're damaged then you need to assess the state of the crankshaft etc. and you can work out your options of repair or replacement.

I will have the endoscope by Tuesday so will start with that and try to identify the source of the knock/rattle with the big stick.
I remember seeing the old mechanical fitters at work locating worn bearings etc. with a large screw driver pushed (yellow end ) into thier ear.

[Desiro]

A little update

I have not had the second opinion yet but have got the car home.

Looked down the plug holes with the endoscope and there is not much to see, pistons look in good condition but cannot see the valves.

I span it up with the plugs out and the oil pressure light goes out and it does not seem to be too noisey, but I am on my own so its difficult to tell.

I will put the plugs back in and try with the stick.

[freelandm]

Hi Desiro

Sorry to hear this it has happened to me following an oil change unscheduled as well.,mine made the noise when the motor got 3-4k on it and it turned out to be number 5 bearing that had failed no other damage apart from 600 quid to my pocket for re shelling etc.

I see you are only down the road if you need a 2nd opinion go and see the boys at Bavarian motor warehouse in Huddersfield cannot recommend enough, they did my car and diagnosed in about 10th seconds.

Good luck with it.
Matt

[Desiro]

Hi Desiro

Sorry to hear this it has happened to me following an oil change unscheduled as well.,mine made the noise when the motor got 3-4k on it and it turned out to be number 5 bearing that had failed no other damage apart from 600 quid to my pocket for re shelling etc.

I see you are only down the road if you need a 2nd opinion go and see the boys at Bavarian motor warehouse in Huddersfield cannot recommend enough, they did my car and diagnosed in about 10th seconds.

Good luck with it.
Matt

Cheers Matt

£600 Sounds more like it
Strange it happened following an oil change As I said, I had a recent inspection 11 but even if it was related to the oil change I dont see what I can do about it now. I just want to get it repaired

Will give them a call and see what they say.

[freelandm]

Hi Desiro.

I think mine was thrashed around Huddersfield without it been warmed up I used to work at a Indie Lotus garage with the bloke who did the oil change I took it back immediately and they didn't have a clue. Suffice to say the car never went to that place again..

Good luck
Matt.

[Desiro]

It's fixed

First of all thanks to all of you that helped and gave advice particularly JohnWayne who came to my house to help diagnose the problem.

So you dont have to read the whole thread, I lost the tip off a spark plug cylinder 5. Note to self "have the inspection 11 done BEFORE you go on a 2500 mile road trip"

Here are the pics which I think are self explanatory

http://dl.dropbox.com/u/74830617/Z3M%20Piston%20and%20plug%20tip%20005.JPG

http://dl.dropbox.com/u/74830617/Z3M%20Piston%20and%20plug%20tip%20018.JPG

http://dl.dropbox.com/u/74830617/Z3M%20piston%20and%20plug%20tip%20022.JPG

http://dl.dropbox.com/u/74830617/Z3M%20Piston%20and%20plug%20tip%20042.JPG

The repair was done by Geoff Steel Racing.

The major components replaced were:-

Piston x1
Rings X6
Oil pump
All bearings
ARP conrod bolts

GSR did the first 100 miles after rebuild and I have done a further 250, so far it's running sweet

[Jonttt]

Desiro,

The direct link to your dropbox will not work for anyone who already has their own dropbox account (as it will simply connect to their own account). I'm not sure if it will even work for anyone without a dropbox account.

I think you need to setup a public subfolder for this type of sharing

[Gazza]

Dropbox is asking me to sign in

[Desiro]

I'm new to dropbox I'll try again

Done I think?

[PCSAM]

pics up from me .hope OP is ok with it

[Damon]

I had shell bearings go after an oil change by a main dealer. Engine full of swarf. Mine was also low mileage. People on other boards and forums are recommending different oil as a possible solution. Castrol Edge 10w60. I don't see how that could stop bolts stretching though. I only mentioned it as it seems I'm not the only one to have them go after an oil change.
Anyway, I'm now going to use 10w60 and I don't bounce it off the rev limiter as often as I used to.

[gookah]

ok, we have seen the physical damage, now what we want to know is, what the real 'damage' was .

[pingu]

No damage to the bore or cyl head?

The bit of debris looks bigger than the chip out of the piston.

If I had the engine that stripped, I would have balanced all the components +/- 1g (BMW tolerance is +/- 5g). Do Geoff Steel offer that service? I know they do performance upgrades as I have them bookmarked ready for a performance clutch next year.

[c_w]

So just to clarify was the original diagnosis wrong (and also the thread title)?
And the damage to the piston was caused buy the spark plug debris? (and the source of the noise?)
and new shells/bolts fitted as a precaution whilst the piston was replaced?

[Desiro]

ok, we have seen the physical damage, now what we want to know is, what the real 'damage' was .

Not telling

[Desiro]

No damage to the bore or cyl head?

The bit of debris looks bigger than the chip out of the piston.

If I had the engine that stripped, I would have balanced all the components +/- 1g (BMW tolerance is +/- 5g). Do Geoff Steel offer that service? I know they do performance upgrades as I have them bookmarked ready for a performance clutch next year.

I did a compression test very early on and one cylinder was lower than the others but so negligible I thought it unlikely to be a scored bore. GSR did not say it was scored.
Are they sleeved?

No damage to the head acording to GSR. I assumed the pistons were a softer material to the head?

Yes it was balanced, will called me to reccomend it as they had the equipment to do it. I was led to believe if not balanced then all pistons would have to be changed.

ps I'll try the bit in the hole to see if it fits but it looks the same shape so probably will.

[Desiro]

So just to clarify was the original diagnosis wrong (and also the thread title)?
And the damage to the piston was caused buy the spark plug debris? (and the source of the noise?)
and new shells/bolts fitted as a precaution whilst the piston was replaced?

Yes c_w the original diagnosis was wrong but while the engine was stripped, I thought it was prudent to change all the components which are likely to fail in the future.

The original diagnosis did not make sense because of it quietening down when warm. I honestly think that until stripped down nobody could have made an acurate diagnosis.

it was expensive but I have a really good and hopefully reliable engine now. It may just be in my head but it seems more responsive and much smoother

Done 500 miles now and Sunday did a very enjoyable trip to Whitby from wetherby. Thanks deano for the itn.

how long should I run it in for?

[Deano1712]

Can you let us know what caused the problem?

Sent from my GT-I9100 using Tapatalk 2

[Desiro]

Can you let us know what caused the problem?

Sent from my GT-I9100 using Tapatalk 2

The problem was caused by the spark plug electrode burning off and attaching itself to the top of the piston as per photo's.

I don't know if the noise was caused by piston slap due to unburnt fuel in that cylinder as you suggested earlier or the piston with extra piece hitting the cylinder head.

Just to clarify I checked and the electrode fits like a jigsaw piece into the piston.

Why did I loose the tip? I dont know, maybe higher octane fuel than normal sometimes 100 RON

Maybe driving hard at high altitudes.

Maybe not doing the insp. 11 before setting off.

Hopefully you can see the photos

http://dl.dropbox.com/u/74830617/High%20mountain%20pass.jpg

http://dl.dropbox.com/u/74830617/Typical%20mountain%20pass.jpg

http://dl.dropbox.com/u/74830617/Zeddy%20in%20the%20mountains.jpg

http://dl.dropbox.com/u/74830617/The%20route%20des%20Grands%20Alpes.jpg