I was checking my fluids at work earlier and noticed this vacuum hose (?) that appears to have degraded to the point that it has now collapsed upon itself. I snapped a couple pics but didn't have to time to trace back where it came from. Truck has been running fine and I haven't noticed any issues.

I'll dig in a little deeper and fix it once finals week is over.

In the mean time, can anyone tell me what exactly this hose does?

It's the narrow hose attached to the drivers side of the yellow/white T-connector

 

That i believe goes to the vacuum canister (or accumulator) in your fender. on earlier model trucks that canister was on the under side of the hood but then in what ever year it got moved to inside the fender. controls your 4WD and some other things.

Have fun getting that line back on when you take it off lol.

 

Thanks, I also just found this thread https://blazerforum.com/forum/2nd-ge...hose-go-64903/ which also helped.

I suppose that would explain why my heat isn't working very well

 

I would agree with cherry that looks like what it is......