Flywheel has come loose!!!!

[sammygon1]

Having just installed my new flywheel a couple of weeks ago, the old one had its teeth ground down, I've just had to pull the engine back out due to some odd scraping sounds. I thought the TO bearing was maybe bad or I did something weird with the clutch, like not tightening the pressure plate down, etc. It turns out my flywheel has come loose, the bolts are still firmly in place but the flywheel has some big wiggle room behind them. Well I just looked at my torque wrench and it only goes to 95ft/lbs not the recommended 110ft/lbs. How did I let that one slide by me?

My question: Should I heat the bolts ( I installed them using loctite) and turn them in tighter, or heat them and back them out then reinstall with loctite. Thanks, for your help, Sam

[surflvr911sc]

Scary!

There are at least two different length flywheel bolts. If you torqued them to 95ft/lbs and the flywheel is still loose, you might have the wrong ones. The holes in the crank are deeper than they are threaded, more torque might get things tightened up but it’s not a very good idea.

You should be able to pull them w/o heat, and then check the threads to see if they started to strip on the ends, sure sign that they were too long.

[anh911]

Yep, they are either the incorrect bolts or you may be missing the washer that goes under them. (not sure what motor you have?)
Take it off and be sure there's no serious damage at the crankshaft mating surfaces. Measure the bolts and let us know.

[Superman]

That's frightening. I can only imagine the damage a loose flywheel could do in there. At 6000 rpm, the outer edge of that flywheel must be travelling at a bazillion miles per second. Actually, it's only 300 feet per second if the circumference is three feet, but still......

I'd have to agree that very possibly you have the wrong bolts. At any rate, you have paperweights now, or at least that's what I would promote them to. I do not reuse flywheel bolts, and I suggest you not reuse them either.

But back to the bolt length thing. 95 lb/ft should have seated that flywheel nicely, and in fact should also have held forever. IN other words, I doubt that a flywheel or fasteners would fail if properly torqued to 95 lb/ft, even if the spec is 110. IN order to have a loose flywheel, you'd almost certainly have to have the wrong bolts.

[CHILI]

I was told to tighten down (using a star pattern) to something like 85lbs, then take one at a time out and use lock tite and re-install and toque to some unglodly #. I guess it was 110 lbs. Can't remember now, but it was tight! Do that for each one, but of course, one at a time and still in a star pattern.

Maybe the others are right. Wrong bolts?

[Rot 911]

Originally posted by CHILI
I was told to tighten down (using a star pattern) to something like 85lbs, then take one at a time out and use lock tite and re-install and toque to some unglodly #. I guess it was 110 lbs. Can't remember now, but it was tight! Do that for each one, but of course, one at a time and still in a star pattern.

Maybe the others are right. Wrong bolts?

What????? the flywheel bolts stretch and should only be torqued one time!

[anh911]

Can you imagine a flywheel launch at 6000 rpm? that would just ruin your day - period.

[surflvr911sc]

Ingo, Tyson, and I were just talking about the flywheel bolts the other day. Tyson said that he thought there was a Tech bulletin on the bolts a while back that said they can be reused and many other manufacturers reuse them. I figure that they are cheap enough that it’s not worth the risk.

I don’t agree w/ Chad’s method but it shouldn’t hurt anything. If you are only doing a partial torque then they wont fully stretch (if they are even designed to) until the final torque spec is reached. A better way that would accomplish the same thing would be to apply the lock tight, partial torque, then final torque. Star pattern, always.

[addictionMS]

I am willing to bet your source for the torque setting is a Haynes manual, it is wrong, the torque spec is something like 66ft-lbs in the Bentley manual, if you use new bolts and torque to 115ft-lbs you run the risk of breaking them (had a friend break two that way)

Anyone have a Bentley manual handy to check,

having said that I have used red loctite a few times with the original bolts, and had no problems.

Jim

[CHILI]

Originally posted by Kurt V
What????? the flywheel bolts stretch and should only be torqued one time!

I've read that, too. I've read and heard so many contradicting things, I don't know what to go with any more. Hehehh And I'm not just talking about flywheels.

The good news: They've been in for about 2 1/2 years (about 10K miles) with no problems. And to make everyone cringe, I re-used the bolts that were in it!!!! Take that!

[sammygon1]

The torque spec comes from Wayne's 101 projects book. I am going to pull out the bolts and check the flywheel for damage. I do have the correct washer that goes with them. I also ordered these bolts new from Pelican so I don't think they are the wwrong ones but I'll measure them to make sure. Sam

[addictionMS]

pretty sure about the torque spec in the bentley book....should check it.

Jim

[ChrisBennet]

There is a reason for putting the bolts in before putting the Loctite. Clay Dopke has gone off to tend his horses last I knew but before he did he left some pearls of wisdom. Here's one:

Subject: Re: Threadlock on flywheel stretch bolts
From: DopkeDesgn@aol.com
Date: Sun, 21 Mar 1999 14:56:24 EST
X-Message-Number: 32

David,

Use Loctight red 271. bolt the flywheel with two opposing bolts to
the crank. Only then apply some 271 to a bolt and insert it and tighten.
Repeat for remainder of bolts including the initial two you started with.
Reason: if flywheel is not mated solid to the crank, some of the red will get
behind the flange and cause just enough of a miss match to loosen flywheel
after awhile.

Ten years ago at Daytona we lost two flywheels because of locktight
behind the flange. It took someone much smarter than I to point it out to me.
Never lost a flywheel after that.

Clay Dopkd
dopke/design Motorsports

[Damomma]

The flyweel nut on my other project car (a Maxda RX-7) requires 350lbs of torque. Doesn't make the 110 seem so bad huh? And I have to rebuild that thing a lot more than my 911!

Jim

[CHILI]

That sort of supports what I was told to do. Although I was told to use all of the bolts to "seat" it down, then use the locktite. I just read my first post and noticed I said 85lbs. Typo, sorry it was 65lbs. Maybe 65lbs isn't enough to stretch bolts that will be torgued to over 100lbs in the end????

[Tim Walsh]

Just a datapoint. My trusted mechanic who's been in the business since 1973 said he always reuses the flywheel bolts and never had one break, snap or come loose. I couldn't trust my faith in that so I went with new.

[ChrisBennet]

Ed Broadhead and I were talking about this a while back. He reuses them. I looked in my manuals and it wasn't until the 964 that Porsche recommended replacement of the flywheel bolts.
-Chris

[john walker's workshop]

66# on 9 bolt flywheels, 115# on the 6 bolt ones. there has to be a spacer ring under the bolt heads on the 6 bolt units. check the end of the crank, and the crank mating surface for damage from being run loose.

[anh911]

Sources:
early tech spec book, Haynes, Bentley, 930 Factory suppliment, Wayne's book.
Just as John said, the M10s used in the 9 bolt are 65. The m12s used in the 6 bolt are 108.

There are only minor variations between all the manuals.
65-66 on the m10s and 106-110 on the m12s.

I have reused them with no problems but these days when you buy a "complete" engine kit they come with it so why not?

Edit: I should be more specific. I have reused the 12mms but won't be reusing the smaller 10mms.

[addictionMS]

well I stand corrected, I guess I have only worked on 3.2 recently, so I have the 65# number solidly in my head.

now should I ever work on an older engine with the M12s I will know better


thanks for looking that up

jim