cutting the Gordian Nut

[Dash01]

Lots of issues regarding the 36mm collar nut that holds the harmonic disk at the front of the engine: This nut must be removed before the timing chain, guide rail, seal, etc. can be changed.

Although attached with ~317 ft. lbs. of torque, many here have reported that it takes MUCH more torque than that to remove it--perhaps several times as much torque. One guy even said that both he and his friend could not budge the nut even with both hanging from a 5' breaker bar, which suggests ~1,500-2,000 ft lbs. of torque was insufficient to loosen the nut. Others have reported that the crankshaft securing tool may be twisted or mangled in the attempt to remove the big nut. Use of an impact wrench necessitates ~12" of clearance behind (or removal of) the radiator and AC condensor, which would entail de-pressurizing and then recharging the AC system.

The 36mm nut costs about ~$5, and probably the old one should not be re-used anyway.

So, why not just cut off the old one with a Dremel Tool and/or nut splitter? On reasssembly, clean the threads of the crankshaft, add Loctite, and then torque the nut to 317 ft. lb. spec. while securing the crankshaft by jamming a cold chisel into the flywheel teeth.

Your thoughts?

[skr]

it will come off if u pull hard enough. i did it with the engine off, with a "special tool" bolted to the balancers hub . i broke a hex key on it (22 mm on m21) but eventualy it came off. (1.5 meters bar helped).
cutting it/drilling it out doesn't rrealy seam doable as it's a M18 12-9 class bolt. it other words it's extremly hard, or they don't come much harder than this.
oh, and if you loctite it, it ain't coming off again

[E34-520iSE]

The pulley bolt on my M20 engine was EXTREMELY tight. I only got it loose using a chunky 3/4" drive socket, a fixed type 3/4"drive bar and 5 foot of scaffolding tube slid over the top of the drive bar. I had someone in the car holding the brake pedal(car in 1st gear) and me outside giving the scoffolding bar some major heave ho! It slackened in the end, and I only needed a few inches of clearance to get the socket on and the bar up past the top of the engine. You may need to remove the bonnet first. I dunno if this will help you but it may help someone with an M20.

HTH,

Shaun

[SnakeyesTx]

You can't get a 1/2" drive breaker bar and impact socket in there and just bump it with the starter till it breaks loose? It's always worked for me on just about any motor I've ever worked on so far. Also.. 317 ft/lbs?! WTF? you'd think the stud would break or the threads would strip first.

I guess if worse comes to worse you could always borrow a "Torque multiplier" type wratchet good up to 15000 ft/lbs.

[Dash01]

~317 ft. lbs. or torque is just what's called for in putting the 36 mm nut ON the car. After ~17 years, it's sometimes pretty well fried on there, so some guys have reported that REMOVAL has effectively meant sometimes well above ~1,000+ ft. lbs. to pry the nut OFF.

Since some folks say never to use hardware twice, I am wondering about just cutting the old 36 mm nut off, then replaceing it with new nut at proper torque spec.

[DaveVoorhis]

I think the trick will be finding something that will cut that hard little bastard.

[nizmainiac]

i had no problem getting mine off my m20 engine, i just put it in 4th gear and put the handbrake on, you could use a short piece of scafford tube on the breaker bar, that might help

[Felixdacat]

I agree with snakeyes. I have done the same thing for many a car. Haven't had any problems.

[calmloki]

Ditto dat on using the starter and a breaker bar - worked for me on a M20 and a M30.

[genphreak]

Been there, done that. Cutting it is hell, but possible. And potentially messy, you will damage the crankshaft's threads without a doubt.

Just use some scaffold pipe, go buy a half inch breaker bar and a 1/2 37mm socket. Spray some penetrant on the night before JIC it can help. If the car is still running, do it 2 weeks before as the heat/cool cycles might help the penetrant penetrate!

It's a fine machine thread so won't let go until you cut it in two. My mate and I still hung off the thing with a breaker bar to no avail when it was 2/3 through. We were cutting extremely carefully, the pressure was hard on the thread and did not release incrementally as we thought it might.

WHen we did mine, (which is an auto and had the head off so the motor was moving freely). I had no other way to get the nut off. It pays to use your nut in situations like these.

Don't cut. Its tough. Its a bastard but its harder and more dangerous to cut it. If manual you can chock the car and heave.

Q: Why did God make automatic cars in the first place? Were we not lazy enough for him?

A: He wanted to cause the complete downfall of the human race.

(You can probably guess that I dislike auto trannies)

Nick

[Dash01]

Well, perhaps the 525i engine apparently has considerably less stress on the big nut than the 535i engine, which is a different animal.

Consider the reports of some posters who say that even with a 4-5' breaker bar and one or two full grown men hanging on it, the nut may not come loose. Further, consider the reports of the steel crank securing tool being twisted in the process. This means that even though "only" ~317 foot pounds of torque was applied to the nut on installation, it may sometimes take well over 1,000 pounds of torque to remove it from its fried-on mode after only 17 short years of use.

Consider what's happening in such a high-torque nut removal: ALL of that stress is travelling through the tiny woodruff key on the flange, through the threads on the end of the crankshaft, and through the nut itself. So, the 36 mm nut would be, upon removal, the veteran of years of use, hardening, and mega-stress upon removal. Do I really wanna put that thing back on my car?

Some smart folks say never to use a bolt or nut a second time. That, and the fact that a new 36 mm nut costs ~$5, tells me it might be easier and alot cheaper to cut the old nut off with a Dremel tool disk, thereby sparing the flange, crank, threads, and crank securing tool lots of potential stress. It would also mean not having to mess with the expense and difficulty of getting an impact wrench into the limited space in front of the engine. Hence the title of my post: cutting the Gordian Nut. (That was a pun, in case you'd not noticed.)

I'm hoping Bill R, Jeff, and others well seasoned in the M30 engine will chime in here, with their insight and advice, BEFORE I cut metal.

[calmloki]

AHEM. People who have done it, me among them, have already told you how to remove the bolt without pissing about with a Dremel. Shock gets it off mo' betta than hanging a great weight on the end of a pole. Worked for my 325i AND my 533i M30. Start with a hot battery - might take a half dozen licks. You think the mechanics in the group are using dremels to take off that bolt??


<
Well, perhaps the 525i engine apparently has considerably less stress on the big nut than the 535i engine, which is a different animal.

Consider the reports of some posters who say that even with a 4-5' breaker bar and one or two full grown men hanging on it, the nut may not come loose. Further, consider the reports of the steel crank securing tool being twisted in the process. This means that even though "only" ~317 foot pounds of torque was applied to the nut on installation, it may sometimes take well over 1,000 pounds of torque to remove it from its fried-on mode after only 17 short years of use.

Consider what's happening in such a high-torque nut removal: ALL of that stress is travelling through the tiny woodruff key on the flange, through the threads on the end of the crankshaft, and through the nut itself. So, the 36 mm nut would be, upon removal, the veteran of years of use, hardening, and mega-stress upon removal. Do I really wanna put that thing back on my car?

Some smart folks say never to use a bolt or nut a second time. That, and the fact that a new 36 mm nut costs ~$5, tells me it might be easier and alot cheaper to cut the old nut off with a Dremel tool disk, thereby sparing the flange, crank, threads, and crank securing tool lots of potential stress. It would also mean not having to mess with the expense and difficulty of getting an impact wrench into the limited space in front of the engine. Hence the title of my post: cutting the Gordian Nut. (That was a pun, in case you'd not noticed.)

I'm hoping Bill R, Jeff, and others well seasoned in the M30 engine will chime in here, with their insight and advice, BEFORE I cut metal.

[gale]

If I'm not mistaken, that bolt is already Loctite'd from the factory. It's not the tightness of the bolt that's keeping it from loosening, it's the threads themselves. If you cut the bolt head off, then how will you get the remaining threads out of the crank once the harmonic balancer is removed? All that will be left to torque on is a stub of the sawed off bolt and the threads will still be as stuck as before and you'd be at the mercy of a pipe wrench to grip on a short stub of threads.

I did the timing belt on my Toyota V8 this past winter and used the "breaker bar tucked under the chassis trick with the starter" and it spun the bolt off just that fast & the crank can take the momentary one-time torque-age required to do it.

Many years ago I helped a friend swap a new longblock into his 02. The instructions that came with it suggested heating the bolt to break down the Loctite if a breaker bar wouldn't budge it.

[winfred]

3/4" breaker bar and 36mm socket from harbor freight will kill the nut-o-doom, a 1/2 impact won't touch it my big 3/4 ingersol will suck em off but they are rather pricy and take lotsa air, 3/4 breaker bar with a few feet of pipe will get it just fine if you can lock the crank from turning