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Broken flywheel bolt

I guess the title says it all....

While tearing down a 2.4T MFI engine I have for a total rebuild and removing the flywheel, one of the bolts sheared off below the surface of the end of the crank.

How to remove?

Did some reading and it sounds like EDM is the best way to go....but who can do that?

Drilling out the center of the bolt, and using either an EZ-out or tap, sounds problematic at best.

Because the broken end of the bolt is recessed into the end of the crank, unlikely you can weld a nut on the end and break it lose that way.

Anyone out there had this issue before?

Looks like corrosion and time may have compromised the bolt.
Good reason to always put new flywheel bolts in when you re-do the engine.
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Old 06-11-2016, 07:20 PM
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Old 06-12-2016, 05:43 PM
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It's a big bolt and they generally are an easy hand turn into the crank. I'd drill and use a stubby spiral easyout.
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Old 06-12-2016, 07:36 PM
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Tig weld a smaller bolt to it (ground to a somewhat point) and turn it out
Old 06-13-2016, 11:28 AM
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Quote:
Originally Posted by turbo nut View Post
Tig weld a smaller bolt to it (ground to a somewhat point) and turn it out
Good suggestion!
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Old 06-13-2016, 11:05 PM
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I'd try Johns suggestion first. If you try tig welding down a hole you best be a very good
welder. I spent hours removing a crank pulley pin that someone had tried welding onto.
Had to grind the hardened end of the crank to be able to mill the pin out.
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Old 06-14-2016, 05:42 AM
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Bolt is broken off too deep into the end of the crank to ever weld a nut on.
And I've broken off too many EZ-outs in my past....won't begin to try that.
Plus weren't these originally torqued on at 110 ft-lbs from the factory? If so, they are not just easily going to back out.

So will be going the EDM route in the near future.
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Last edited by skinnerd; 06-15-2016 at 01:41 AM..
Old 06-15-2016, 01:37 AM
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Unless the bolt has been stretched in the hole or is rusted, it should (should is a key word) turn out with the easy out.
I have broken a few of the square easy outs too but not the spiral type.
They are a pain where you don't need an ache when you break them so I understand why you are hesitant to go that route.
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Old 06-15-2016, 05:05 AM
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x3 on the spiral EZ out. Spot it with a center drill then drill it with a LEFT handed drill. I'd make a drill guide that clamps to the crank so you are drilling straight. You have nothing to lose, the cost to EDM will be the same whether it's just the bolt or the bolt with a broken off EZ out in it. The left handed drill may just back it out by itself. Soak it with ATF/acetone of course. It all depends on what you feel comfortable doing, take it to a shop if you don't feel good about tackling it. If I was doing it I'd fixture the crank in a drill press just because those bolts are so hard and tough to drill with a hand drill. That bolt may have been over torqued and compromised and just waiting to snap, hard to believe there would be much corrosion on those bolts.

Last edited by boosted79; 06-15-2016 at 06:27 AM..
Old 06-15-2016, 06:23 AM
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I agree with the guys that the broken bolt should be no longer highly stressed. The loss of the head has relieved nearly all the elastic energy stored in the remaining piece of bolt. Maybe a little energy left in it if it was locked with red Loctite.

Also agree with boosted79 that drilling the bolt is a bit tough due to the hardened 12.9 class steel that the flywheel bolts are made of. Use a new drill bit & cutting oil to let the drill do it's work without being quickly dulled by the hardened steel. Once you get a decent amount depth in the drill hole, the spiral extractor will be able to do it's job. Especially if you cut the extractor to size so it'll fit your hole nice & tight and then you drive the extractor into the hole with some moderate hammering. The spiral extractors like these are the best type IMO & very strong

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Old 06-15-2016, 07:58 AM
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Maybe use some heat with the ez-out, if it had Loctite on the threads.
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Old 06-17-2016, 09:34 AM
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I've always had good luck heating and then drilling them with a left hand drill bit. Once the bit bites it usually spins the broken part right out.

Ken
Old 06-17-2016, 03:17 PM
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Don't be concerned that the original torque. We are not talking about a pipe thread that has an inherient interence fit to overcome. . These are straight threads. Once the head broke off, there is zero preload on the remaining section of the fastener.
Old 06-18-2016, 04:49 PM
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Drill with a left hand bit, and then easy out.
Old 06-24-2016, 03:07 AM
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If that bolt broke trying to remove it no easy out will even come close. If you can have someone in a machine shop with a mill give it a go or Elox discharge is more than likely going to be the only way.
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Old 06-24-2016, 07:39 AM
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I'll be tackling this likely next week, so I'll keep you posted on how it goes....what works for this case, and what doesn't.
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Old 06-24-2016, 08:05 PM
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The head is broken off , so there is no bolt head to estabilish torque strain on the thds. and there is a good chance the the bolt head was stress fractured prior to snapping.

I have drilled out broken 5/8" and 3/4" B16 bolts that have been in use in super heated steam systems, and first course of action is as described previously and below.

Easily, 60%-70% back themselves out. A little extra pressure to create more heat in the drilling process, is a good idea; as is a penetrating fluid soak for 24 hrs. prior to drilling.

As suggested many times, a left handed drill bit and spiral easy out will do the job.

Be smart enough to blue the borken bolt and with dividers, etch 4 times @ 90 degrees to establish center, and center punch prior to drilling.

Assure good control of the drill if/when the broken bolt backs itself out due to heat and pressure of the drilling process.

HTH
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Old 07-11-2016, 09:23 PM
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Quote:
Originally Posted by Nine9six View Post
The head is broken off , so there is no bolt head to estabilish torque strain on the thds. and there is a good chance the the bolt head was stress fractured prior to snapping.

I have drilled out broken 5/8" and 3/4" B16 bolts that have been in use in super heated steam systems, and first course of action is as described below.

Easily, 60%-70% back themselves out. A little extra pressure to create more heat in the drilling process, is a good idea; as is a penetrating fluid soak for 24 hrs. prior to drilling.

As suggested many times, a left handed drill bit and spiral easy out will do the job.

Be smart enough to blue the borken bolt and with dividers, etch 4 times @ 90 degrees to establish center, and center punch prior to drilling.

Assure good control of the drill if/when the broken bolt backs itself out due to heat and pressure of the drilling process.

HTH
Best answer yet.
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Old 07-11-2016, 10:24 PM
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broken bolt

I have traveled down this road before.Cut the head off an 8 x 1.25mm bolt.Dip the cut end in acid.The top of the flywheel bolt has a rough surface so put a dab of JB Weld on the end of the stud.If you have a 8mm with a head size of 14mm,like from a 356 or 912 you install that on the stud and spin it down so it fits flat with the flywheel surface and now the stud is straight to the broken flywheel bolt.Sit back and have a beer.Wait a few hours for set time of the JB Weld and then back that baby out.If that does not come out then pay the $50.00 for the EDM removal.Fred Apgar
Old 07-12-2016, 05:15 AM
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Boo hoo.....none of the above suggestions worked.
That baby is really rusted in there tight!
Off to get it EDM'd.
Let you know how it all turns out....
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Old 09-05-2016, 08:20 PM
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