Crank Pulley Came Loose
 

Hey everyone,

Bought a used 40th back in September and last night I noticed some minor belt squeak. Popped the hood and noticed the crank pulley wobbling like hell. Put it on a lift and re-torqued. We think the previous owner installed a lightweight pulley and didn't torque correctly. I still need to confirm it is an aftermarket pulley.

So here are my concerns... How would it last for 7 months with a loose pulley? Shouldn't I be worried about what caused it to back out (harmonic vibrations, cracked pulley, etc.)? What should I look for to confirm the engine isn't done for?

A few questions come to mind:

1) Did the wobble disappear after the crank pulley was re-torqued?
2) I assume that the wobble is gone so, is there any noticeable vibration now?

If the wobble is gone and there is no discernible vibration, I would say that you got lucky that there is no lasting effects from the loose pulley.

Pulleys have a pretty tight fit, so even if the bolt loosened up along the way, it would have taken some time for the pulley to move on the crankshaft. I wouldn't be so worried about the engine, but I would replace the belt for sure and while the belt is off, make sure that anything the belt rode on (tensioner, alternator, etc.) still turns easily and that there is no damage to any of the bearings in these components.

Keep up posted as to what you find...

Yes, after tightening the wobble was gone and the car felt 100% better under accel and decel. Unfortunately, with it feeling better I can't really tell if any vibrations are out of the ordinary.

I wouldn't loose any sleep. Modern engines are internally balanced and the claim that a light weight pulley can cause excessive wear and vibration is unproven fear mongering.

Confirmed the pulley is aftermarket. Pretty sure its the AMS pulley that Z1 sells. We took a closer look for any signs of dmg and didnt notice any. Gonna check again in a week or so for any signs of oil leak around the pulley.

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It's an aftermarket aluminum pulley. You might want to remove it and inspect the inside of the fit area. If it was wobbling. It might have egg-shaped the inside. When you retorqued it. It may be just sitting on the flat end of the crank, and not on the circumference fit area.

And yes, an aftermarket aluminum pulley WILL break the crank shaft. I found out the hard way with an LT1 350 I had in my one truck. :shakes head: just google it.

https://www.google.com/search?q=brok...ih=591&dpr=2.5

If the pulley is undamaged you might want to consider lock tie for the threads. I realize that they are popular but do consider the fact that the OEM pulley and flywheel are engineered to absorb and counter balance various types of engine and transmission vibrations. They wouldn't use these types of parts if they could simply bolt on light weight stuff. Sorry just my opinion.

Be sure to check if there is a Woodruff key that the key and the grooves it resides in on the crank and the pulley aren't worn smooth or rounded/radiused on the edges. That's bad if so. It MAY not have a woodruff key but I haven't seen many that don't.