I recently had my b16a2 rebuilt - new crank, pistons, rods, bearings, etc. Within 2000 miles, however, my engine has lost out - new crank's bolt for external pulleys sheared off yesterday while cruising at around 40 mph. The mechanic who did it wants to see the now immobile car and broken bolt himself before he will even agree he may have overtorqued it, and I am trying to figure out if anything else could have logically caused the bolt to shear off like that.
Any help is greatly appreciated.
---Matt

Short of a defective bolt... I don't know of one. Its essentially identical to the B16A1 I am familiar with.That part of it anyway....there are a lot of other differences between the first and second generation versions of this engine.

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Originally Posted by smoothy

Short of a defective bolt... I don't know of one. Its essentially identical to the B16A1 I am familiar with.

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And those are the only two possibilities I could think of, as well. Are there any other telltale symptoms of an overtorqued crankshaft bolt (anything that may have occurred during operation)?

Thanks for the response. It doesn't help to know I have to fight now, but it's at least calming to know I likely couldn't have done anything wrong.

You can measure the two halves when you get it out. An over-torqued bolt will be longer because it will stretch right before snapping. That is a torque to spec bolt, not a torque to yield bolt where a designated stretch is expected... (that type are single use items that need replaced each use.)

The crank pulley is keyed Only goes on one way. Don't see how YOU could have done anything. Unless that bolt was previously over-torqued at some point before the rebuild. Damaged and finally failed

You are sure it broke off, correct? Meaning you have the both parts or just the half still in the crank. And didn't fall out from being under-torqued.

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Originally Posted by smoothy

You can measure the two halves when you get it out. An over-torqued bolt will be longer because it will stretch right before snapping. That is a torque to spec bolt, not a torque to yield bolt where a designated stretch is expected... (that type are single use items that need replaced each use.)

The crank pulley is keyed Only goes on one way. Don't see how YOU could have done anything.

You are sure it broke off, correct? Meaning you have the both parts or just the half still in the crank. And didn't fall out from being under-torqued.

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It broke clean off, yea. It's sitting in my car at the Dobbs who helped me after I lost power steering right now, but I can try to get a picture sometime later today. The other half is still in the crank, since we have not taken it apart to see if old crank is salvageable with a new bolt yet or not - master mechanic who did the job (my uncle) will have to make that call.

In theory it should be extractable (and maybe easily) since it should have any forces pulling against the threads removed... unless he used locktite. And the crank fine as long as the crank snout wasn't damaged when it all came apart when driving.

If it broke off flush with the end of the crank...more extraction options exist.

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Originally Posted by smoothy

In theory it should be extractable (and maybe easily) since it should have any forces pulling against the threads removed... unless he used locktite. And the crank fine as long as the crank snout wasn't damaged when it all came apart when driving.

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He was asking about the snout - now, I understand why. With any luck, we should be able to get it back on the road nice and quick, then. Fingers crossed the snout wasn't damaged and we can do a (relatively) quick extraction/exchange of parts! Not in the mood for another rebuild... and I know he isn't, either. He doesn't deserve to lose out on this...

Proper technique is crucial when you install crank pulley bolts. They are usually installed wet (clean engine oil), except for the contact surface between the bolt's head and the washer. It goes without saying that you need the correct torque spec from the shop manual and that you use an accurate torque wrench. I cannot see how it would shear off, unless it was improperly torqued.

Lot of if's, maybe's and it depends... could be as little as 20 minutes or so to fix once he has a new bolt if you are lucky and has enough protruding to grab and it comes out without an effort, to a whole lot more.

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Originally Posted by smoothy

Lot if if's, maybe's and it depends... could be as little as 20 minutes or so to fix once he has a new bolt id you are lucky, to a whole lot more.

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It depends if the crank is INDEED salvageable, or not. If not, we need a new crank, and to pull and reassemble it all over again... my mind never shuts up once it starts stressing. I've been researching this since yesterday afternoon.

Thanks again for helping me troubleshoot. It's nice to at least know I couldn't have done anything to hurt her.

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Originally Posted by TxGreaseMonkey

Proper technique is crucial when you install crank pulley bolts. They are usually installed wet, except for the contact surface between the bolt's head and the washer. It goes without saying that you need the correct torque spec from the shop manual and that you use an accurate torque wrench. I cannot see how it would shear off, unless it was improperly torqued,

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He's a master mechanic, and a good one, at that. I've never seen him botch a job, so I'm assuming it was just a defective bolt was accidentally used. He immediately went on the defensive when I called yesterday, and I can understand why - I don't want him losing out on this, but I obviously need to get my car back up and running asap. And safely, this time.

I'd be interested to know how he removed the crank pulley bolt. I use a 40" breaker bar and a crank pulley holding tool, to remove the crank pulley bolt. I've seen people try all kinds of techniques to get the bolt out, because very few impact wrenches even faze them. It's possible the bolt was damaged during removal, especially if he used a breaker bar and starter motor rigged set-up.