I have a 1999 Jeep Cherokee XJ. Like most XJs of this age, the vacuum line that runs from the engine compartment to the vent control inside the cabin is brittle and cracked. I have been able to patch it with some shrink tubing, but it is now beyond repair. I searched for threads on replacing this line but didn't find any. Does anyone know the procedure for replacing this vacuum line. Can you get to the backside of that line by taking out the glovebox? I was going to remove the vent/temp control to see the backside but didn't get to it tonight. It's the vacuum line circle in the pictures.

 

Looked closer today. Thanks to Jonny the Jeep engineer, replacing that line is a heater box removal job. The cluster of vacuum lines runs behind he heater box. I was able to shove a plastic tube alongside the line from the engine compartment but could not get it to come out the top side. I may try again with the curve going up from the engine compartment. What a pain. And I am definitely not replacing the whole vacuum line harness. I see some on eBay. If I have to get the heater box out, I'll just do a splice job. It feels like the lines inside the cabin are all still flexible. They really should have put a junction at the firewall so the short piece could be replaced. You can suck it Johnny the Jeep engineer.

Vacuum lines coming from behind the heater box

Vacuum lines going to the control ****.

 

Watched a DeXJs video and I see two options. Push the hard plastic line through the hole and it should pop out on op of the heater box and then splice into the right line. Or.....Push a line through the antenna opening on the passnger side, route it behind the glovebox and splice it in. Either way, would beat the R&R of the heater box.

From DeXJs video

 

Looks like I found a way to fix it without removing the dash and heater box! Ihad some stiff vacumm line from a Mercedes (that in dash vacuum system was crazy). I was able to push it through the foam baffle from the engine compartment side and it came out behind the glove box. Now I just need to splice it into the black flexible vacuum line and should be good to go. I may look for some slightly thinner hard vacuum line.

 

Props to you for undertaking "a swine of a job". Heater core is a tough one. Thanks for sharing.