Nitsud40i

I bought this 97 jeep grand cherokee about 2 years ago and it has had a bad vacuum leak ever since..Finally got around to tracing the lines and surprisingly all my lines inside engine bay are good.. I found my bad spot which is where the t connector splits off and goes inside the firewall. There's nothing left to splice (was about a inch sticking out tried to touch it and it was so brittle it fell apart again..SO now it's inside my firewall..tore most of my dash apart (except dropping steering column and pulling upper dash) and i can see where it connects to the air control switch. The lines are brown,green,res,black andy yellow. I can see them go up and disappear behind the hvac housing.. How does the vacuum line connect to these air control switch lines?? Basically i need to know if there is any way i can cut these lines and reroute to engine for vacuum at the t connector? Or how can i trace the broken vacuum line inside the firewall without removing the whole hvac housing? Or is there anyway to bypass it?? It has been cold af here and im sick of only defrost heat/no cruise control. Pls help! Pic of vac lines that connect to heat selector switch..how do they connect to the main vacuum line?

CoffeeCommando

I tore my dash apart years back to replace the heater core. I remember looking at the vac controls to try to remember which one fed the rest. I would think you would be able to find it in a manual but I don't know.

You might search out "heater core" and see if someone has done a write up. You might get some in depth pictures that give you the clue you are searching for.

Nitsud40i

I have a Haynes service manual and can't find it anywhere in here unfortunately..I can't seem to find anything online to help either i have been searching for 2 days now (which is why i made an account here to post and ask the pros)
The only diagrams i can find are one that is for vac lines in engine and it says it T's off to the heater,but can't find any schematics of the lines once they go inside the firewall. This is the only thing i can find (does this mean the black line is the main vac line?? If so can i cut that one and reroute it to the engine bay to hook up the the vac line in there? Or do i need to cut all of them and splice all 5 into one line and hook that line to vac lines in engine bay?
Sorry for dumb questions i am a noob when it comes to this,any help is appreciated!

CoffeeCommando

Yep, you can. There's nothing else inside of there that is supplied vacuum except for those controls. Have you tried fishing a coat hanger with a pre-formed curvature through the firewall? I know that won't be easy but it's an alternative. That spot with the firewall entry will leak water and provide an entry point for bugs if you don't seal it. I've seen an army of those tiny **** roaches under people's floor carpeting when trying to trace the AC evap drain.

Make sure all firewall holes are sealed. Something you could, and maybe might want to do, is something that I will be doing. I'm going to drill a hole that is accessible and seal it with a cable gland. You can get a package that comes with several in assorted sizes and use them however you like. For hoses, or wires. I'm going to be creating a switch panel with about 10-12 switches and will run all my wiring for it through one of those. It will be water tight as long as you drill the correct size hole for the size you use. I have a step-bit that goes up to 3/4" I think from Greenlee that I got for a good price on Amazon. It will drill through mild steel so a firewall isn't an issue.

Cable Glands:



They thread in and the end of it threads down tight and encloses a rubber ring around whatever is in the middle (cables, hoses, etc.)

wingless

That broken black vacuum supply line is routed only to the HVAC vacuum connector.

Do a solid splice and route the replacement line through the firewall, sealing around the opening.

CoffeeCommando

That picture is worth gold. I wish I would have taken pictures when I took mine apart.

dave1123

The black line that says vacuum reservoir is the heater control supply line. you can use rubber hose that slides over the plastic tubing and it can go anywhere thru the firewall. A good place is the rubber seal around the base of the steering column or the throttle cable gasket. A little bit of RTV silicone around the tube will seal it because it doesn't move. I've seen the entire tube circuit replaced with rubber hose using a barb T fitting for connecting everything. Just keep the check valve near the intake manifold in the circuit. You should be able to find fittings at NAPA on the "Help" carousel.

Jgaun1

I am having the same problem and didn't quite understand all the answers. Does black line coming through firewall connect to black line coming off heater climate control?