Rod bolt won't torque to spec

[Helmsman]

Originally Posted by Bubbles

Not throw cold water in this but I stripped the last oil pickup bolt during a bearing swap. I chalked it up to wanting to get the project complete and being too comfortable. A bit of duct tape and luck got me out a potential disaster. It happens to all of us and the tech may have forgot to flip the switch on the impact gun and wanted out of the oil drip shower.

In my mind definitely something like this happened. Hopefully the shop has an insurance that will pick this up. Over here I believe theres even law to have one, cause sh@t does happen.
Like when the main dealer poored MT fluid into my DCT..."they never would...!" but yes turned out they did. 15k euro + labour to replace the box, which assumingly their poor insurance company picked up.

[GearKid]

Originally Posted by Helmsman

In my mind definitely something like this happened. Hopefully the shop has an insurance that will pick this up. Over here I believe theres even law to have one, cause sh@t does happen.
Like when the main dealer poored MT fluid into my DCT..."they never would...!" but yes turned out they did. 15k euro + labour to replace the box, which assumingly their poor insurance company picked up.

Thank you for the ideas! I believe we have the following root cause theories:
1-old prestretched OEM bolt was retorqued using "stretching procedure" which subjected the rod to over torquing
2-impact wrench was used to break the bolts loose, but the wrench accidentally tightened the bolt instead
3-rod was compromised due to a pre-existing condition, perhaps from day 1, or due to a previously botched job where someone left all the old parts in place.

Did I forget any?
Anyone want to place any bets?
Better yet, any ideas for how to narrow down the list?

[Scharbag]

Originally Posted by GearKid

Thank you for the ideas! I believe we have the following root cause theories:
1-old prestretched OEM bolt was retorqued using "stretching procedure" which subjected the rod to over torquing
2-impact wrench was used to break the bolts loose, but the wrench accidentally tightened the bolt instead
3-rod was compromised due to a pre-existing condition, perhaps from day 1, or due to a previously botched job where someone left all the old parts in place.

Did I forget any?
Anyone want to place any bets?
Better yet, any ideas for how to narrow down the list?

1-TIS is clear, the old bolts are totally fine to use to test clearance - this is not a cause of your problem unless they were improperly used.

2-Unless they were using a LARGE impact and held if for many ugga-duggas, this is likely not the case - but if they did hit it with a big impact, damage may be plausible.

3 - I would doubt very much that the engine would have lived with a bad rod bolt - ask SYT_Shadow about that...

[SYT_Shadow]

Originally Posted by Scharbag

1-TIS is clear, the old bolts are totally fine to use to test clearance - this is not a cause of your problem unless they were improperly used.

2-Unless they were using a LARGE impact and held if for many ugga-duggas, this is likely not the case - but if they did hit it with a big impact, damage may be plausible.

3 - I would doubt very much that the engine would have lived with a bad rod bolt - ask SYT_Shadow about that...

bad rod bolt --> Kaboom!

[GearKid]

Originally Posted by Scharbag

1-TIS is clear, the old bolts are totally fine to use to test clearance - this is not a cause of your problem unless they were improperly used.

2-Unless they were using a LARGE impact and held if for many ugga-duggas, this is likely not the case - but if they did hit it with a big impact, damage may be plausible.

3 - I would doubt very much that the engine would have lived with a bad rod bolt - ask SYT_Shadow about that...

Thanks for dispelling these theories. From what I'm gathering, the only way to strip a rod is to grossly over torque it. Does anyone have a sense what that number is?
Also curious about another detail. I've seen many posts confuse 130 degrees with 130N-m for the OEM procedure. What's the final N-m value when the OEM angle procedure is used? Just wondering if it's anywhere near 130N-m.

[SYT_Shadow]

Originally Posted by GearKid

Thanks for dispelling these theories. From what I'm gathering, the only way to strip a rod is to grossly over torque it. Does anyone have a sense what that number is?
Also curious about another detail. I've seen many posts confuse 130 degrees with 130N-m for the OEM procedure. What's the final N-m value when the OEM angle procedure is used? Just wondering if it's anywhere near 130N-m.

I estimate somewhere in the 50-60 ftlb range

[Bubbles]

Originally Posted by Helmsman

In my mind definitely something like this happened. Hopefully the shop has an insurance that will pick this up. Over here I believe theres even law to have one, cause sh@t does happen.
Like when the main dealer poored MT fluid into my DCT..."they never would...!" but yes turned out they did. 15k euro + labour to replace the box, which assumingly their poor insurance company picked up.

Interesting, that insurance option may be country specific. I wasn’t aware of this but I never take my vehicles to the shop anymore, except for new tires.

[Helmsman]

Originally Posted by Bubbles

Interesting, that insurance option may be country specific. I wasn’t aware of this but I never take my vehicles to the shop anymore.

I don't either if I don't have to. Yeah, this specific dealer better keep their insurance... Haven't been there since (DCT happened 2015) but now forced by my insurance company to visit guess who...due to sporadic DCT issues. Yikes.

[GearKid]

Originally Posted by Helmsman

I don't either if I don't have to. Yeah, this specific dealer better keep their insurance... Haven't been there since (DCT happened 2015) but now forced by my insurance company to visit guess who...due to sporadic DCT issues. Yikes.

My sentiments as well. I figure if I can break my own stuff for free why pay someone else to do it for me. I opted for the rod bearing repair to be done at a shop since I'd be doing on my back under jack stands on a sloping curbside without the right tools...figured I'd be safe with the shop.

[TX]

Wow, I was away a few days and sure missed a thread here.
There have been dozens and dozens of people doing DIY replacements in their garages on jack stands, with any combination of tools. There have been several hundred installs by any number of shops that I can name. This is an absolute first that I am hearing of a shop stripping a rod doing a simple quick clearance measurement. Something doesn't add up, I wish you the best, but man I'd have some real serious questions for the person working on your car. I can only assume it was a major screw up with the impact wrench or angle torqued way beyond reasonable limits. Anyone have a bent rod they can toast and measure with a digital 150+ft lbs wrench when it strips out so we can have a log?

[BayE30]

so this happened at a local bay area ahop? what shop was it?

[GearKid]

Originally Posted by BayE30

so this happened at a local bay area ahop? what shop was it?

It was a highly recommended one, especially for BE bearings....

[Macpsi]

my thought process is, when the tech was dissembling and the bolt did have some ripped threads on it why not shoot a picture of it immediately? Are the stock rod bolts coated with anything? Could see if they used a high powered impact the wrong way by checking the head of the bolt for any nicks/chips from the impact hitting against the bolt head during tightening/loosening.

[GearKid]

Originally Posted by Macpsi

my thought process is, when the tech was dissembling and the bolt did have some ripped threads on it why not shoot a picture of it immediately? Are the stock rod bolts coated with anything? Could see if they used a high powered impact the wrong way by checking the head of the bolt for any nicks/chips from the impact hitting against the bolt head during tightening/loosening.

I'm at a loss too. I've yet to pick up the car but hopefully all the old bearings and bolts are available. If so I'll look carefully at these bolts and take lots of pictures . I can tell you there won't be thread debris. There won't be any since the bolt threads are wider than the shank. Any thread material would be removed as the bolt made its way through the intact zone of threads. (The first 1/2 inch or so of threads is not in contact with the bolt's threads when torquing down so these will be intact.)

Shop is pretty firm on their stance that this was pre-existing, so let's go from there.
Theory to support this claim:
In the recent past, someone messed around and must have ever so slightly over tightened that one bolt. The rod bearings are stock and look to be consistent for the motor's mileage. That implies guilt on the former party, so instead of installing new bearings they put everything back together and put the car up for sale. The new owner drives the car for 500 miles since purchase and brings it in for new bearings. The tech goes to retorque that partially compromised bolt and it fully strips before getting half-way to spec.
Is this possible? Absolutely, but it would be easier to swallow if alcohol were involved...

[pbonsalb]

If you bought the car used, I guess you will never know. Maybe that is best. But I am sorry you have had an expensive and bad initial experience with the M3. A car should not need rod bearing replacement at 50k or 100k or 150k miles, but enough of these motors have failed that many of us think this preventative maintenance is a worthwhile expense to offset the risk of a much more expensive failure and there have been almost no cases of the job being done wrong.

[SYT_Shadow]

One thing I don't understand is how a rod bolt could ever strip the rod in the first place. I'm sure the bolt would snap before tickling the rod itself.

Then again, we have had forum members buy cars and then the engines grenade on their way home...

[Bubbles]

Originally Posted by GearKid

I'm at a loss too. I've yet to pick up the car but hopefully all the old bearings and bolts are available. If so I'll look carefully at these bolts and take lots of pictures . I can tell you there won't be thread debris. There won't be any since the bolt threads are wider than the shank. Any thread material would be removed as the bolt made its way through the intact zone of threads. (The first 1/2 inch or so of threads is not in contact with the bolt's threads when torquing down so these will be intact.)

Shop is pretty firm on their stance that this was pre-existing, so let's go from there.
Theory to support this claim:
In the recent past, someone messed around and must have ever so slightly over tightened that one bolt. The rod bearings are stock and look to be consistent for the motor's mileage. That implies guilt on the former party, so instead of installing new bearings they put everything back together and put the car up for sale. The new owner drives the car for 500 miles since purchase and brings it in for new bearings. The tech goes to retorque that partially compromised bolt and it fully strips before getting half-way to spec.
Is this possible? Absolutely, but it would be easier to swallow if alcohol were involved...

If you have the appetite to use this shop, negotiate free/significant discount install of the new motor. Since this is so unusual, I can’t see how a reputable shop doesn’t met you halfway here.

[ha9981]

Originally Posted by GearKid

I'm at a loss too. I've yet to pick up the car but hopefully all the old bearings and bolts are available. If so I'll look carefully at these bolts and take lots of pictures . I can tell you there won't be thread debris. There won't be any since the bolt threads are wider than the shank. Any thread material would be removed as the bolt made its way through the intact zone of threads. (The first 1/2 inch or so of threads is not in contact with the bolt's threads when torquing down so these will be intact.)

Shop is pretty firm on their stance that this was pre-existing, so let's go from there.
Theory to support this claim:
In the recent past, someone messed around and must have ever so slightly over tightened that one bolt. The rod bearings are stock and look to be consistent for the motor's mileage. That implies guilt on the former party, so instead of installing new bearings they put everything back together and put the car up for sale. The new owner drives the car for 500 miles since purchase and brings it in for new bearings. The tech goes to retorque that partially compromised bolt and it fully strips before getting half-way to spec.
Is this possible? Absolutely, but it would be easier to swallow if alcohol were involved...

That story is very very unlikely. Moreover whenever something goes wrong like this it shows up on a forum or Facebook group. If the last owner screwed up they'd have asked how long it would last if they just closed it up.

If it was compromised from before, how did it survive this long.

Something really stupid happened when this shop dropped the oil pan. We will never know what exactly what happened.

[rantarM3]

Perhaps they used the wrong rod cap (or opposite of how it should go), which may have misaligned the threads just enough for them to get stripped. They discovered the mistake, put the correct cap back on, and gave you a call. Just conjecture...

Don't they start the bolt by hand? I would be surprised if anyone would just put the bolt in and immediately hit it with an impact wrench. Surely they would have noticed that the threads were engaging farther into the rod. Threads are unlikely to be damaged on disassembly, especially when the upper threads are fine.

Another theory - someone used an OEM bolt, torqued it up, bolt snapped in the middle of the threads allowing that section of the bolt to spin and damage its threads as the upper part of the bolt prevented it from moving further into the rod.

[GearKid]

Originally Posted by rantarM3

Perhaps they used the wrong rod cap (or opposite of how it should go), which may have misaligned the threads just enough for them to get stripped. They discovered the mistake, put the correct cap back on, and gave you a call. Just conjecture...

Don't they start the bolt by hand? I would be surprised if anyone would just put the bolt in and immediately hit it with an impact wrench. Surely they would have noticed that the threads were engaging farther into the rod. Threads are unlikely to be damaged on disassembly, especially when the upper threads are fine.

Another theory - someone used an OEM bolt, torqued it up, bolt snapped in the middle of the threads allowing that section of the bolt to spin and damage its threads as the upper part of the bolt prevented it from moving further into the rod.

Here's my latest thought that may explain this stripped rod. Let's say a former owner swapped out the bearings at 45k or something like that. New OEM bearings and bolts go in. This rod and maybe the others were significantly over tightened. Maybe instead of 130 degrees they were tightened to 130Nm or ft-lbs. this was not enough to strip the threads initially but after running the motor for 30k miles the threads start to break loose. The rod holds together because the upper threads keep the bolt from pulling out. Everything stays tight until the current shop pulls it all apart and starts to tighten down that rod again. The tech gets only half way to spec when those threads completely fail.
If this is true then we may see similar issues as motors are opened up a second time.

[Helmsman]

Originally Posted by GearKid

Here's my latest thought that may explain this stripped rod. Let's say a former owner swapped out the bearings at 45k or something like that. New OEM bearings and bolts go in. This rod and maybe the others were significantly over tightened. Maybe instead of 130 degrees they were tightened to 130Nm or ft-lbs. this was not enough to strip the threads initially but after running the motor for 30k miles the threads start to break loose. The rod holds together because the upper threads keep the bolt from pulling out. Everything stays tight until the current shop pulls it all apart and starts to tighten down that rod again. The tech gets only half way to spec when those threads completely fail.
If this is true then we may see similar issues as motors are opened up a second time.

I would also desperately be looking for a reasonable explanation when being in a tight spot between what seems to be a proper shop and the result. But this can't be that logical answer in my mind. If the bolt was that bad over tightened, it wouldn't make sense that 1) The tech didn't notice, and if he did, just put the engine back together. 2) The thread started to break loose and still kept up fine just to fall apart at second run.
There is a reason to why the rod bolts are extremely strong, holding back the highest load in the engine. If thread where broken I believe the cap would have started to move resulting in significant signs.

I know the situation when debating with people who have plenty more experience and knows better than yourself, while obviously still are quite able to make mistakes. Getting them to admit is...challenging. Have a similar story with a boat yard reg my boat, plain aweful but we can't take the blame for others shit.

[Helmsman]

Originally Posted by GearKid

Here's my latest thought that may explain this stripped rod. Let's say a former owner swapped out the bearings at 45k or something like that. New OEM bearings and bolts go in. This rod and maybe the others were significantly over tightened. Maybe instead of 130 degrees they were tightened to 130Nm or ft-lbs. this was not enough to strip the threads initially but after running the motor for 30k miles the threads start to break loose. The rod holds together because the upper threads keep the bolt from pulling out. Everything stays tight until the current shop pulls it all apart and starts to tighten down that rod again. The tech gets only half way to spec when those threads completely fail.
If this is true then we may see similar issues as motors are opened up a second time.

I would also desperately be looking for a reasonable explanation when being in a tight spot between what seems to be a proper shop and the result. But this can't be that logical answer in my mind. If the bolt was that bad over tightened, it wouldn't make sense that 1) The tech didn't notice, and if he did, just put the engine back together. 2) The thread started to break loose and still kept up fine just to fall apart at second run.
There is a reason to why the rod bolts are extremely strong, holding back the highest load in the engine. If thread where broken I believe the cap would have started to move resulting in significant signs.

I know the situation when debating with people who have plenty more experience and knows better than yourself, while obviously still are quite able to make mistakes. Getting them to admit is...challenging. Have a similar story with a boat yard reg my boat, plain aweful but we can't take the blame for others shit bro.