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Help! Metallurgy Experts & Engine Experts

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posted on Apr, 23 2009 @ 09:34 PM
I am putting this in the technology section because it is a technology related question regarding tool working on metal. The science of metal applies here. The brightest people I know are on ATS. I need a 'mini' scientific forensic analysis. Mods: If this is in the wrong place, please forgive me and move it to the right place.

My friend did a camshaft change and the crankshaft pulley fell off at an idle a few weeks later. I think he might have made a mistake doing the job and he tried to fix it. Are there any engine/metallurgical experts out there that can tell me what happened or might have happened? It looks like tool marks or grinding work on the pulley which shoul be smooth. Thank you in advance.

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posted on Apr, 23 2009 @ 10:27 PM
It looks like the crank bolt wasn't torque properly and either stripped out or backed out.... It should have made some outrageous noise before coming loose. The scoring on the inside along with the wallowed out keeper key slots, makes it to have been loose for quite some time.... The cracked and broken piece on the outer edge would have happened when it separated from the shaft.... How does the shaft look?

posted on Apr, 23 2009 @ 10:35 PM
Not installing it correctly is what caused it, too many variables to tell which part of the job got messed up.

It looks friction related, due to stress or heat IMHO.

He must have over torqued it or had the belt incredebly too tight.

They are made of a softer metal then the crank, so in theory the crank might still be OK.

As stated above, if there are no marks on the crank, just throw a new pulley on.

If it doesn't rattle, you might have saved a ton of man hours to replace the crank.

posted on Apr, 23 2009 @ 10:50 PM
You are right it looks like some one screwed up and tried to add metal then tool it out to make seem fixed. That is not how the pulley should look. I have an 05 gto and the parts are very refined. Never are there any tool marks. The chip could have been from it falling off. I would definatley ask some questions. Anyways if it fell off at idle the crank should be fine. check and make sure they didn't strip the crank bolt. Chec for any play in the crank at the front bearing. Pobably broke when they tried to pull it without removing the crank bolt, seen it before, then tried to repair it.

You cannot repair a broken crank pulley or harmonic balancer. They have to be perfectly balanced or they will fail. I only hope for your sake it did not damage the bearings.

posted on Apr, 23 2009 @ 11:04 PM
The broken pieces on the outside of the harmonic balancer look like it was possibly hit with a hammer to drive the pulley on or a puller was used improperly to cause those cracks. If the cracks formed and pieces lost, it would have thrown the harmonic balancer out of balance and could have caused the crankshaft bolt to snap off. It would have undergone severe vibration if the outer piece(s) came off. That would have then resulted in the keyway being wallowed out. As hypervigilant asked already, how does the end of the crankshaft look. The keyway slot especially on the crankshaft. If it is wallowed out, you will have one or two choices on repairing it. Either replacing the crankshaft or using an industrial remetalizer to repair the keyway. I used to work for a company that sold these type of epoxy rematelizers for use in heavy and maritime industry that was used for many things, one being repairing keyways. Belzona or other industrial remetallizers.

Here is the Belzona website where you can see repairing keyways is one application:

I would need a photo of the crankshaft with keyway visible to see if it needs to be repaired or replaced. I used to do ship propeller shaft in destroyers, tankers, etc and almost every type of keyway application there is in heavy industry. It is critical to do proper preparation before applying these type of compounds. The remetalizers are machinable when dried, as long as you have done the surface prep and repair as instructed.

If the crank shaft and its keyway are not damaged, you can get another harmonic balancer from a salvage yard, and the bolt, and install a new key and torque the crankshaft bolt to the proper torque specifications. I would also use a little Loctite Threadlocker Red 271 on the crank bolt to make sure it doesn't vibrate loose.

[edit on 23/4/09 by spirit_horse]

posted on Apr, 23 2009 @ 11:34 PM
I haven't actually seen the end of the crank. I took it to a shop that works on high end cars and they bought a new pulley and they are having a hard time putting it on because the end of the crankshaft is damaged.

Here is the funny part to all of this. This crankshaft does NOT have a keyway! I know, I am just baffled as to what happened to the pulley/crank. Everything seemed to be working fine, then I fired it up one day, the alternator indicated problems, so I stopped the engine.....and thi is the result. I am just baffled by the fact there wasn't a keyway but the pulley looks like there is one.

Thank you so much for your help with this.

posted on Apr, 24 2009 @ 08:55 AM
In all my years, I have never seen a crankshaft without a keyway. Usually it is further in on the crankshaft that you can't see without looking directly in or taking the timing cover off. Well, good luck with getting it resolved.

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