ive replaced some of the vacuum lines but i left one untouched....i dont know were it goes and i dont want to mess anything up..I do know that it goes down behind the back of the engine though...Im thinking it goes to the heater but not sure..any help someone....Its a 4.3L 6 cyl vortec...
Thanks

 

The vacuum system is not all that complex on your truck (EVAP system aside). You will have a vacuum line running from the engine to the check valve/'t'. From there, it will run to the HVAC system (into the firewall), the vacuum reservoir (ball), and to the 4wd system (down to the transfer case) if so equiped.

 

yea i have already change the one that goes to the vacuum reservoir and to the 4 whl drive system....basically all the ones that come from that check valve t....isn't that the little plastic piece that has like 3 or 4 vacuum lines coming from it????Ive changed all of them but the one going through the firewall....i just dont know if there is anything that i can mess up following it down there or something....cause i dont got the money to replace anything right now

 

It goes into the cab and controls your HOT/COLD door flap and selector switch for your in cab heat. Its up under the dash and might not be easily accesable but is doable.

 

aight man thanks