Flywheel bolts won't stay tight!

[Woods Crasher]

So here's the story. Whoever removed this flywheel before completely messed up the threads in the back of the crank when they put it back on...

One of the best Nissan techs at my job managed to drill and tap all 8 flywheel bolt holes to 7/16 x 20. I went and bought some high grade machine bolts and the flywheel was torqued to 78 foot pounds with thread locker. Drove it for about a week, put like 200 - 400 miles on the car. and I felt a vibration in the shifter. Then it would vibrate a lot when I let off the throttle. and THEN I felt it in the freaking clutch pedal.

So I have the car parked at the shop. What the heck am I going to do. Am I going to have to get a new engine? or at least a crank? can I do the crank from the bottom of the car?(looks like it would be a pita) I so upset at the moment that after all this time and hard work that something I can't do anything about is broken
Modified by Woods Crasher at 3:57 PM 5/15/2007

[240 Trainee]

You are suppossed to use some loc-tite on the flywheel bolts, if you didn't that would partially explain them backing out.

Hopefully you didn't mess up the new threads your mechanic tapped in the crank.

[bentvalves]

stock setup or modded?

we are dealing with that same problem on a porsche race engine at work this week, and the conclusion is that detonation is whats loosening the flywheel.

not nasty piston pitting detonation, but just enough where its rocking things to and fro and loosening ****.

your crank and flywheel mating surfaces may need to be machined, so keep that in mind.

[Woods Crasher]

You are suppossed to use some loc-tite on the flywheel bolts, if you didn't that would partially explain them backing out.

Hopefully you didn't mess up the new threads your mechanic tapped in the crank.

yes....I used red loctite.

stock setup or modded?

we are dealing with that same problem on a porsche race engine at work this week, and the conclusion is that detonation is whats loosening the flywheel.

not nasty piston pitting detonation, but just enough where its rocking things to and fro and loosening ****.

your crank and flywheel mating surfaces may need to be machined, so keep that in mind.

Almost stock...S14 t28 at stock boost.

[mbmbmb23]

Try putting a lock washer under each bolt.

-m

[Zero260]

I may have missed something, but did you take it apart and see the bolts were backing out, or are you guessing?

[ca18datsun510]

crank pulley.

[bentvalves]

if your on the stock ECU, Id rule out detonation.

you could have a balance issue with that flywheel?

[Woods Crasher]

crank pulley.

what about it. It was tight

[ca18datsun510]

is the rubber in it good?

if if its out of balance or not dampening it can cause vibration in the crank that will cause the bolts to come loose.

not absolutely the problem, but its possible.

[Woods Crasher]

is the rubber in it good?

if if its out of balance or not dampening it can cause vibration in the crank that will cause the bolts to come loose.

not absolutely the problem, but its possible.

I'll definitely check it out once I get a chance to look at the car. Thanks for the input.

[wewders]

I may have missed something, but did you take it apart and see the bolts were backing out, or are you guessing?

I was wondering the same thing.

[Woods Crasher]

I was wondering the same thing.

Unfortunately I've become an expert on what a loose flywheel sounds and feels like and how it behaves...

No I have not had a chance to pull the trans, but those bolts are either backing out or broken.

[dash]

is your tq wrench accurate ? I only use bean type tq wrenchr the bolts bottoming out slightly ?oe bolts purposely have a very fine thread, is the pitch on the new bolts similar ?Does the shank on the new bolts (part without threads) fit tight in the flywheel bolt holes ?I never locktite any flywheel bolts, no probs here.