Rod bolt won't torque to spec

[Properstyle]

the shop may not have messed up during install but I said as soon as you posted this. The Rod threads were tripped. NO way around it. What caused it could be a mirred of things but more likley is defect rod or bad install at some point if you are not the original owner who so to say po didn't have them done and a rod was over tq'd witha factory bolt.

[GearKid]

Originally Posted by Properstyle

the shop may not have messed up during install but I said as soon as you posted this. The Rod threads were tripped. NO way around it. What caused it could be a mirred of things but more likley is defect rod or bad install at some point if you are not the original owner who so to say po didn't have them done and a rod was over tq'd witha factory bolt.

Great point. The original bearings and bolts are there, but anything is possible including someone going in there years ago and unbolting stuff. It does seem hard to image the motor not self destructing with a loose bearing cap. This could be a case of bad luck on the part of the tech unbolting what was already a compromised rod. Odds and common sense appear to be saying otherwise.
I'm really curious to hear of this issue. I didn't find any discussion on stripped threads so I have no idea of how often it happens. My hope is the shop helps me out somehow. The motor was running fine before it was opened up, so there must be some value to it. What would it be worth with a bad rod?

[Properstyle]

Originally Posted by GearKid

Great point. The original bearings and bolts are there, but anything is possible including someone going in there years ago and unbolting stuff. It does seem hard to image the motor not self destructing with a loose bearing cap. This could be a case of bad luck on the part of the tech unbolting what was already a compromised rod. Odds and common sense appear to be saying otherwise.
I'm really curious to hear of this issue. I didn't find any discussion on stripped threads so I have no idea of how often it happens. My hope is the shop helps me out somehow. The motor was running fine before it was opened up, so there must be some value to it. What would it be worth with a bad rod?

yeah man is rough situation. I change rod bearings on numerous E9xms and ive never seen it even on a broken rod but luck of the draw you never know. hope you and the shop come to good conclusion with this.

[Davisca455]

Originally Posted by Scharbag

If the rod bearing did not spin, and that seems to not be the case here, then there is no chance of "heat damage" to the rod.

Maintenance and upkeep has very little to do with how your bearings look.

I would get another opinion from a professional before allowing the shop off the hook.

Keep us up to date.

Cheers,

Here is my #7 rod bearing at 65,253 miles.
This car was meticulously maintained its entire life.
There were zero indications that anything was wrong with my car before I changed bearings, even the Blackstone report was clean as a whistle.
Zero issues with my BE Bearing installation.
The extra heat theory reeks like sweaty ass, to me.
I seriously doubt that your rod was damaged prior, because I would imagine it would have windowed your block.

[SAMM3Y]

Any pics of the bolts that came out? I would imagine it would have been dragging thread with it.

[Davisca455]

Originally Posted by SAMM3Y

Any pics of the bolts that came out? I would imagine it would have been dragging thread with it.

Yes, pictures of the rod as well.
Like is the rod all discolored?

I guess the type of question I would have:

What could explain stripping the threads of a connecting rod?

Previously yielded conn rod threads due to overheating of the rod bearing?
(is the rod discolored?)

Poor manufacturing of that 1 rod by BMW?

Previous owner yielded the rod threads?
(Are there any clues that these aren't the original bearing shells, or that the crankcase has been previously invaded?)

Reusing Torque to Yield bolts and that torquing process to check clearances?
(Could this over stress the rod threads?)

There are more questions for sure... but which of these seems the most likely, so far?

...and the thing that lit up my Spidey Senses was the claim that "the crank is out of round, so you need a new engine anyway..."
In my skeptic's mind, it was translated to "Nothing to see here folks, keep moving along, pay no attention to the stripped threads..."

And maybe they didn't do anything wrong, but the BE bolts are not 1 time use like the BMW bolts are, so it seems like they'd be better off using the BE bolts to check clearances in the future.

[Davisca455]

...sorry, if turns out that reusing one time use BMW bolts and re-torqueing them using the BMW torque procedure can cause a thread failure, I'm not sure I'd be comfortable replacing just the one rod assembly.

[GearKid]

Originally Posted by Davisca455

Yes, pictures of the rod as well.
Like is the rod all discolored?

I guess the type of question I would have:

What could explain stripping the threads of a connecting rod?

Previously yielded conn rod threads due to overheating of the rod bearing?
(is the rod discolored?)

Poor manufacturing of that 1 rod by BMW?

Previous owner yielded the rod threads?
(Are there any clues that these aren't the original bearing shells, or that the crankcase has been previously invaded?)

Reusing Torque to Yield bolts and that torquing process to check clearances?
(Could this over stress the rod threads?)

There are more questions for sure... but which of these seems the most likely, so far?

...and the thing that lit up my Spidey Senses was the claim that "the crank is out of round, so you need a new engine anyway..."
In my skeptic's mind, it was translated to "Nothing to see here folks, keep moving along, pay no attention to the stripped threads..."

And maybe they didn't do anything wrong, but the BE bolts are not 1 time use like the BMW bolts are, so it seems like they'd be better off using the BE bolts to check clearances in the future.

Agreed on all points.
I inspected the bolts and they all looked perfect. Not a trace of thread material. We spent some time discussing the missing thread material and even went into the rod itself with a scope. You could see the missing section of threads and a very small fragment that was peeling away from the rod, but nothing that accounted for what was missing. Because the bolts have a narrow shoulder compared to the threaded section, any thread material will be left behind when the bolt goes through the intact threads on the rod. To be clear, the stripped area is about a half inch down into the rod's threaded section.
I guess the shop was trying to pick out those lose threads this afternoon with a little progress. They also managed to get the APR bolt to catch enough intact threads to torque down to 50 ft-lbs, but they could tell it wasn't a fully captured bolt. We don't even want to start the motor up for fear of that rod end pulling loose.

[GearKid]

Originally Posted by Davisca455

...sorry, if turns out that reusing one time use BMW bolts and re-torqueing them using the BMW torque procedure can cause a thread failure, I'm not sure I'd be comfortable replacing just the one rod assembly.

My thoughts as well. To go to the trouble of pulling the motor and doing just a partial overhaul makes no sense.

My latest plan is to have Dinan build one of their 4.2l motors using mine as the core. It's more expensive than the cheapest option for sure but a 0mile motor has its appeal. I feel somewhat reluctant to throw a new motor into an old chassis though despite it being in nice shape

[SYT_Shadow]

This sounds like a nightmare from hell. What the fuck are they doing installing a used OEM rod bolt? Dumbasses

Contact a lawyer.

[GearKid]

Originally Posted by Davisca455

Here is my #7 rod bearing at 65,253 miles.
This car was meticulously maintained its entire life.
There were zero indications that anything was wrong with my car before I changed bearings, even the Blackstone report was clean as a whistle.
Zero issues with my BE Bearing installation.
The extra heat theory reeks like sweaty ass, to me.
I seriously doubt that your rod was damaged prior, because I would imagine it would have windowed your block.

You provide a perfect example of the bearing issue, where there's no (obvious) correlation of frequent oil changes and damage free bearings. Your bearings look no better than mine, so my car's maintenance history shouldn't necessarily be assigned to the root cause.

[SYT_Shadow]

Originally Posted by GearKid

You provide a perfect example of the bearing issue, where there's no (obvious) correlation of frequent oil changes and damage free bearings. Your bearings look no better than mine, so my car's maintenance history shouldn't necessarily be assigned to the root cause.

a car's maintenance does not bend cranks, or rods, or strip rod bolts. That is crazy town BS

[Scharbag]

I would be very surprised if the threads were stripped prior to disassembly.

1. The stresses in an engine at 8000RPM would have identified that issue ages ago.
2. Rods are built of very stout materials - I have never heard of one being stripped - typically bolts break before threads do
3. The thread engagement of a rod bolt is extraordinarily deep (IIRC ARP recommends 1.5*diameter for thread engagement which rod bolts more than exceed) - the weakest part becomes the bolt shaft (typically right where the treads start), not the threads - hence rod bolts breaking

I would love to be able to take a look at this engine for myself.

Cheers,

[Scharbag]

Originally Posted by SYT_Shadow

a car's maintenance does not bend cranks, or rods, or strip rod bolts. That is crazy town BS

To be fair...



If you forget to do any maintenance and ignore the idiot lights, technically this lack of maintenance can cause rods to bend and cranks to be damaged...

Bolts being stripped? I've got nothing...

But I am just being a cheeky twat.

[Davisca455]

Another question to ask them:

"Hypothetically, If I could actually prove there is nothing wrong with the strength of the rod, by an outside material analysis lab, and if got one or more engineering materials experts that calculated that your process, using used BMW bolts and the BMW torquing procedure, caused the rod threads to be over stressed, would you be willing to take responsibility?"

[NeverL8]

What shop was it?

[Davisca455]

Originally Posted by TheRussski

What shop was it?

Maybe play that card later?

...and the missing thread material may have been on the BMW bolt, and that could explain why it wasn't on the BE ARP bolt?

[Davisca455]

Originally Posted by SYT_Shadow

This sounds like a nightmare from hell. What the fuck are they doing installing a used OEM rod bolt? Dumbasses

Contact a lawyer.

Yes, I'm not sure what real information can be learned about clearances when using a different bolt and a different torque.
Seems like you are learning something completely useless, if you are going to do the final install with a different bolt and a different torque.

[Ajolives]

I'm thinking there's a 5% chance the shop is innocent. Just such an odd situation to happen without outside interference. I would bet there was foreign material on the threads - ripped the thread when they went to torque. Makes sense to me as the first couple threads are apparently spotless

[GearKid]

Originally Posted by Davisca455

Yes, I'm not sure what real information can be learned about clearances when using a different bolt and a different torque.
Seems like you are learning something completely useless, if you are going to do the final install with a different bolt and a different torque.

I feel I may have inspired this practice of checking clearances because I specifically asked them to do it. Upon request I was charged an extra hour's worth of labor, so it may have been a change in the technician's process. My headspace for the request developed after reviewing the BE Bearing warranty (see point 4 in the pic). I also wanted at least some evidence the new bearings were near the target clearance. Of course I expected these measurements to be made with the new hardware. I'm not sure what use the old bearings and bolts offer for understanding clearances.

[GearKid]

Originally Posted by Ajolives

I'm thinking there's a 5% chance the shop is innocent. Just such an odd situation to happen without outside interference. I would bet there was foreign material on the threads - ripped the thread when they went to torque. Makes sense to me as the first couple threads are apparently spotless

You're absolutely reasonable! The tech's story is the bolt never hit anywhere near the torque spec, implying a pre-existing issue. The shop owner was thinking the threads could have been damaged when the bolt was broke loose during disassembly. This is like a frozen bolt pulling the threads with it. Problem here is the rod's threads "above" the bolt's thread pattern were perfect. I would think if threads were truly frozen on the bolt then the bolt would have dragged those frozen threads right through all the rod's threads and buggered them all.

[Davisca455]

Originally Posted by GearKid

You're absolutely reasonable! The tech's story is the bolt never hit anywhere near the torque spec, implying a pre-existing issue. The shop owner was thinking the threads could have been damaged when the bolt was broke loose during disassembly. This is like a frozen bolt pulling the threads with it. Problem here is the rod's threads "above" the bolt's thread pattern were perfect. I would think if threads were truly frozen on the bolt then the bolt would have dragged those frozen threads right through all the rod's threads and buggered them all.

But if the clearance check, using the OEM bolts and torque procedure, preceded that, would that not also fall into the pre-existing conditions bucket as well?