Mystery bolt found in bilge

[eyedocwood]

Found this bolt in the bottom of my bilge today. Volvo 5.7 GI. Any ideas where it came from? I can't see any bolts missing. It's 1/2 SAE. Thanks!

 

[cyclops222]

NO extra charge.
I have found tools left by mechanics.

 

[alldodge]

Welcome
Alternator or power steering maybe

 

[ESGWheel]

Agree with AllDodge. This is flange head bolt which is typically used in those applications and the fact that this one has that wasp waist indicates it was worn down over time > the bolt came slightly loose, and the vibrations of the pump / alt wore it down until someone replaced it. Check every single bolt associated with pump, alt, idler pulley, belt tensioner.

Question: do you have (or did you have) a lot of belt dust in line with the belt (dust pattern is like the belt is spinning off water and it also collects on block behind the belt)? Belt dust looks like fine back specs. This is an indication something wrong with the components the belt is turning (loose, out of line, rusted pulley, etc.)

 

[Mc Tool]

That bolt ain't worn thin ....its stretched to death . Check the thread pitch where the bolt is thin and you can see the difference . Hopefully someone actually replaced the bolt and maybe either dropped or threw the bolt into the bilge .

 

[ESGWheel]

That bolt ain't worn thin ....its stretched to death .

Oh my, you are right! Wow….

 

[dingbat]

That bolt ain't worn thin ....its stretched to death . Check the thread pitch where the bolt is thin and you can see the difference

I disagree.
The pitch at the Major looks pretty consistent.

Flanged head, black oxide bolts are almost always hardened, typically grade 8. They don’t stretch, they break.

I agree with the others…..the alternator would be my first guess.

 

[Scott Danforth]

Measuring the pic with a ruler shows it's stretched.

 

[ScottinAZ]

yep, that bolt is smoked..... definitely stretched just below the head.... likely someone just tossed it carelessly into the bilge and got a new one....

its a fairly small bolt, so likely off the accessory drive somewhere.... could be alternator, power steering or the engine driven water pump.... appears about the right size to be the one that holds the adjustment, rather than the "pivot" bolt... you would know if one of them were missing pretty quickly when you tossed a belt...