00 LS V8, what's this?

[DuKeNoMaD]

What is this bolt blocking?

 

[joegr]

That's the heater coolant bleed. There's supposed to be a plastic screw there. Looking at the bolt size, the end of the bleed hose must be messed up.

 

[Blk04LS]

Yeah as Joe said, that's the cooling system bleeder hose. Someone probably damaged the original plastic insert or it failed due to age (or more likely abuse) and they lazily replaced it with a bolt.

 

[DuKeNoMaD]

Ahh ok thanks boys! Glad I done have a mystery hose!