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Discussion Starter #1
:( as the title says

More detail here 94 VR4 rebuild & upgrade thread

The timing belt and associated drives all look good fortunately.

I'll be pulling it out tomorrow and inspecting for damage and causes.
 

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1994 Mit 3000gt VR4 6spd
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This is a first. Keep us updated
 

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Yes for sure, it has freaked me out.
 

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Yikes. Was it torqued down to specification? Was the washer flattened, or did you replace it beforehand at some point?

-sent from my Galaxy Note 9
 

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I got the Fluidampr in the group buy and it was fitted as part of the full engine and transmission rebuild. New bolt, red loctite and torqued to spec during the build. No reason to suspect a build error, it was methodical and thorough. Zero issues until today ~3,000 miles later. I plan to retrieve it tomorrow, inspect the damage and report back. Researching the topic on the forum, there seem to have been a few instances of bolt head failures and others of bolts backing out.

I fear I'll be fighting the red loctite's grip on a broken-off bolt stub in the crank - that will be fun :(
 

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That really sucks. Sorry to hear that. Definitely let us know what you find out. Also, that's good to know towing companies don't allow for passengers. I'm wondering how they expect a family that was traveling together, to get home, if they happened to break down.
 

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Discussion Starter #7
I retrieved the Fluidampr this morning. I was lucky I didn't loose it, it was resting on the subframe supported by the alternator belt.

The location dowel is sheared off with the stub in the crankshaft - which is a PITA but not the end of the world. Otherwise I may have got lucky. The cam belt drive and all associated components look good. The alternator and power steering belts and associated parts all look good. Best of all the bolt seems to have backed out of the crankshaft completely and the threads look good.

There are some indentations on the end of the crank where it looks like a piece of sheared dowel got trapped for a while.

Getting the Fluidampr back on will be the easy part. Making sure it doesn't happen again is the tough part.

One thing that really concerns me is that the Fluidampr appears to have been located on two separate faces of the crank - the inner face (which is the end of the crank) and the outer edge of the cam drive sprocket. You can see this where the surface finish on the on the inner faces of the Fluidampr have worn off. Its never a good idea to have anything located on two separate axial features like this and can lead to all kinds of bad things during thermal cycling and vibration during running. From my aerospace days, best practice would have been to locate closest to the threaded hole on the inner surface only allowing a gap in the outer face for any tolerance errors in the belt drive sprocket.

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The sheared roll pin is in the timing gear, not the crankshaft, so that should be easier to replace.

When I first installed my Fluidampr I noticed that the bolt got tight before the pulley was fully cinched down (I could wobble the pulley just the tiniest amount). I believe the bolt was bottoming out in the crankshaft before it could tighten down the pulley (Pulley is likely just the smallest amount thinner than the stock one). I ended up grinding the end of the bolt down just a bit until it no longer bottomed out when tightening it. Not sure if this is the case with all of them, but it might be worth double checking (for everyone that has one really).
 

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Discussion Starter #10
Having two separate but simultaneous axial location faces was a huge design no-no back in my aerospace days. Primarily because its practically impossible to share the loads equally and consistently between both faces, so one of them acts like a spring and this can result in lost tension in the bolt - and it backing out.

For an assembly like this, I'd expect the primary location be the inner face (the end of the crank). The cam drive is pressed on so its not going anywhere. A dished spring shim would provide for any axial movement in the cam sprocket.

I think I may use safety wire on the replacement bolt.
 

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Discussion Starter #11
Just heard of another VR4 that lost its Fluidamper after the bolt backed out. I'm trying to make contact with the owner to compare notes. Also had confirmation that having the location shared by two axial faces is a no-no. So it may be a tolerance issue - fixable with a shim.
 

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I would have to pull mine back off again to confirm but I dont believe there was any indication that it was riding on both the crank and the sprocket, just the crank IIRC, but its been a while since I have had it off. Maybe Ill pop it off in the next few days (have to jack the car up and pull the bumper for some stuff anyways) to check as another point of reference.
 

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Discussion Starter #13
It might be a case of tolerance variations. On mine both faces touch but that may not be the case on all installations.
 

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I will double-check mine momentarily but have not heard anything from others. I made sure to use a new cog+pin, new washer (much thicker than a worn out original) and new, revised bolt.

-sent from my Galaxy Note 9
 

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Discussion Starter #15
Where did you get the revised bolt and new washer? I'm reluctant to use the early version with the recessed square drive.
 

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Where did you get the revised bolt and new washer? I'm reluctant to use the early version with the recessed square drive.
I purchased them from Chris/Rvenge during one of my large parts orders. FWIW, I reused Dustin's '96 R/T TT's original stuff (ensured that the washer was not flattened), and his Fluidampr also has around 3,000 miles between SoCal and ND.

Mine checked out fine today** 130ft/lbs immediately clicked and bumped up to 137 afterward. This is with my old Craftsman unit that I had tested against a master set at Matco a few years ago.

 
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I've never used loctite on the crank pulley, but blue might not hurt.
 

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Posting/Sharing on behalf of Jakob and Garrett:

Jakob Hunter said:
Ati dampers are also known to cause the crank bolt to come loose. It’s the nature of the beast, absorbing such a violent range of harmonics causes it. Some locktight and checking every oil change and you should have nothing to worry about
Garrett Chastain said:
This isn’t all that out of the ordinary. ATI from what I’ve seen is better (lost one of those too) they need to be checked often and my negligence has cost me before.
-sent from my Galaxy Note 9
 

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Having two separate but simultaneous axial location faces was a huge design no-no back in my aerospace days. Primarily because its practically impossible to share the loads equally and consistently between both faces, so one of them acts like a spring and this can result in lost tension in the bolt - and it backing out.

For an assembly like this, I'd expect the primary location be the inner face (the end of the crank). The cam drive is pressed on so its not going anywhere. A dished spring shim would provide for any axial movement in the cam sprocket.

I think I may use safety wire on the replacement bolt.
You're off base on this one... The locating face is 100% on the gear. The gear sits proud of the crank and the crank never contacts the balancer. It's done that way to retain the gear. You can't have the gear rattling around beating up the crank and the keyway.

There's also no loctite residue or any evidence those threads had loctite on them. While I don't feel loctite is needed in that application on a properly installed bolt, if red loctite had been used there, not only would we see the evidence, I'm very doubtful that bolt would have ever fallen out.
 

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Discussion Starter #20
I purchased them from Chris/Rvenge during one of my large parts orders. FWIW, I reused Dustin's '96 R/T TT's original stuff (ensured that the washer was not flattened), and his Fluidampr also has around 3,000 miles between SoCal and ND.

Mine checked out fine today** 130ft/lbs immediately clicked and bumped up to 137 afterward. This is with my old Craftsman unit that I had tested against a master set at Matco a few years ago.

Excellent. I really hope I'm an outlier on this issue.
 
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