Mystery bolt found in bilge

eyedocwood

Recruit
Joined
Aug 13, 2023
Messages
1
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!
 

Attachments

  • bolt1.jpg
    bolt1.jpg
    1.9 MB · Views: 22
  • bolt.jpg
    bolt.jpg
    1.5 MB · Views: 22

ESGWheel

Senior Chief Petty Officer
Joined
Aug 29, 2015
Messages
690
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.)
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
16,420
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.
 

ScottinAZ

Master Chief Petty Officer
Joined
Jun 25, 2009
Messages
856
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...
 
Top