kryptronic Posted May 2, 2018 Share Posted May 2, 2018 When I first got my truck there was a broken vacuum line routed through the firewall to the heating and air conditioning unit in the dash. Here's a pic, outlined in yellow. It was broken off where you see the boot I added near the firewall. As you can see, I routed it to a t fitting that routes to the football canister behind the front bumper. Here are some close up shots, in case the image above isn't clear. I did a lot of research and a lot of pics before doing this, but there wasn't any clear info on where this line actually should have gone. So I picked what I thought was the best option. The question is, where does it really go? Anybody have any good shots? 91 HO electronics. Thanks. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 2, 2018 Share Posted May 2, 2018 Do you still have the hot water control valve plumbed into the heater hoses? Cruise control? Link to comment Share on other sites More sharing options...
kryptronic Posted May 2, 2018 Author Share Posted May 2, 2018 Here's a bigger shot from just before I fixed it. Shows more of the heater hoses. Yes, the hot water control valve is plumbed into the heater hoses. Would definitely like to know what that's for, though. Doesn't show up on my YJ. As far as cruise control, the steering column had a cruise control selector, but the wire was cut at the stalk when I got the truck. I have not fully verified all cruise control components are gone, but it is the intention to remove that option entirely if there are any remnants of it. I just haven't gotten there yet. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 2, 2018 Share Posted May 2, 2018 12 minutes ago, kryptronic said: Would definitely like to know what that's for, though. Doesn't show up on my YJ. Would like to help ID it for you, but my vacuum lines are nothing like OEM anymore since I did the new 01 intake manifold. I don't see your vacuum check valve in there either.. Link to comment Share on other sites More sharing options...
kryptronic Posted May 2, 2018 Author Share Posted May 2, 2018 Just now, HOrnbrod said: Would like to help ID it for you, but my vacuum lines are nothing like OEM anymore since I did the new 01 intake manifold. I don't see your vacuum check valve in there either.. Thank you for taking the time to look. If I recall, that line may have dumped to a check valve previously. It looked like the PO tried to fix it incorrectly once or twice and I was guessing because reference pics are non-existent, and the FSM and diagrams I've reviewed are no help with this one. Maybe somebody else with an HO can chime in, perhaps provide a decent pic of how it looks. Basically there are two lines coming out of the HVAC, one white and one black. Anybody know where the black one goes on an HO model? Link to comment Share on other sites More sharing options...
Ωhm Posted May 2, 2018 Share Posted May 2, 2018 Isn't there a vacuum dump valve on the brake pedal for the cruise control? Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 2, 2018 Share Posted May 2, 2018 2 minutes ago, Ωhm said: Isn't there a vacuum dump valve on the brake pedal for the cruise control? Not on an HO. Vacuum goes to the CC servo only. Link to comment Share on other sites More sharing options...
Ωhm Posted May 2, 2018 Share Posted May 2, 2018 Noted: Thanks Link to comment Share on other sites More sharing options...
ParadiseMJ Posted May 3, 2018 Share Posted May 3, 2018 But I don't see a CC servo...on the OP picture...or am I missing something. Link to comment Share on other sites More sharing options...
kryptronic Posted May 3, 2018 Author Share Posted May 3, 2018 Cruise control was an option on the truck but deleted by a previous owner. I have not confirmed it was fully/properly deleted yet. No idea how that's related to my issue, though. Link to comment Share on other sites More sharing options...
kryptronic Posted May 11, 2018 Author Share Posted May 11, 2018 Circling back around on this. If anybody has a 91 or 92 MJ, or even an HO XJ, and can take a pic of exactly what the black vacuum line running out of the HVAC system runs to, I'd appreciate it. Please reference the pics in my original post to see what I'm looking for. There are two lines, a white one and a black one. My black one broke and I have no idea if I have it routed to the right spot right now. Vehicle was optioned with cruise control, but it was removed prior to my ownership. Thanks in advance to anyone that takes the time to help. Link to comment Share on other sites More sharing options...
Keyav8r Posted May 12, 2018 Share Posted May 12, 2018 On my ‘91 there is a tee in the main vacuum line from the reservoir at the firewall near the point the AC lines go through the firewall (also where the vacuum line passes through the firewall). There is a check valve in the connection. I’ve relocated my washer bottle (from a XJ) there to make room for the double diaphragm brake booster so the view in my photo is partially blocked. You can see that tee in your photo but it looks like there is nothing connected to it. Where does the vacuum line that is dangling there go? It look like it may have half of a check valve on the end. Your line is connected at the tee for the cruise control vacuum line. Link to comment Share on other sites More sharing options...
kryptronic Posted May 13, 2018 Author Share Posted May 13, 2018 21 hours ago, Keyav8r said: On my ‘91 there is a tee in the main vacuum line from the reservoir at the firewall near the point the AC lines go through the firewall (also where the vacuum line passes through the firewall). There is a check valve in the connection. I’ve relocated my washer bottle (from a XJ) there to make room for the double diaphragm brake booster so the view in my photo is partially blocked. You can see that tee in your photo but it looks like there is nothing connected to it. Where does the vacuum line that is dangling there go? It look like it may have half of a check valve on the end. Your line is connected at the tee for the cruise control vacuum line. Thank you very much. This should help me figure it out. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted May 15, 2018 Share Posted May 15, 2018 The pink/light vac line at the firewall works the heater valve...when the heat is turned on. If there are any disconnected lines on the passenger side, your HVAC will blow through the defrost only. Link to comment Share on other sites More sharing options...
kryptronic Posted May 28, 2018 Author Share Posted May 28, 2018 Thanks for all the help. Between Keyav8er's pic, a real hard look at the FSM, net searches leading me to other forums, and taking a look at this nice looking 91 MJ I saw at a local show this past weekend, I came up with this. Transfer case and HVAC routed to the same check valve: If this is incorrect for my 91 HO, somebody please let me know. I think I got it though. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 28, 2018 Share Posted May 28, 2018 As I recall, that was the way my 91 was before I moved the vac canister into the cab. Link to comment Share on other sites More sharing options...
kryptronic Posted May 28, 2018 Author Share Posted May 28, 2018 40 minutes ago, HOrnbrod said: As I recall, that was the way my 91 was before I moved the vac canister into the cab. I was staring at pics and the FSM for about an hour when I finally realized every pic I had been provided was for a 2WD model. The FSM referenced HVAC and 4WD vacuum sepearately, but never showed how they connect together vacuum-wise. So through deduction, this is what it looks like the FSM would direct you to do. Thanks for the validation. Link to comment Share on other sites More sharing options...
HOrnbrod Posted May 28, 2018 Share Posted May 28, 2018 On 5/2/2018 at 10:29 AM, kryptronic said: Here's a bigger shot from just before I fixed it. Shows more of the heater hoses. Yes, the hot water control valve is plumbed into the heater hoses. Would definitely like to know what that's for, though. Doesn't show up on my YJ. The vacuum-controlled hot water valve was removed on the later XJs. Most people pull the water control valve, replace the heater hoses with 97+ hoses, then remove the water valve vacuum line. Makes for a much neater install and the all HVAC functions work as before. It does allow continuous water continuously circulation through the heater core, but and heat is blocked out of the cab by the HVAC doors. Unless there's a reason you want to keep the troublesome water control valve. Link to comment Share on other sites More sharing options...
kryptronic Posted May 28, 2018 Author Share Posted May 28, 2018 2 hours ago, HOrnbrod said: The vacuum-controlled hot water valve was removed on the later XJs. Most people pull the water control valve, replace the heater hoses with 97+ hoses, then remove the water valve vacuum line. Makes for a much neater install and the all HVAC functions work as before. It does allow continuous water continuously circulation through the heater core, but and heat is blocked out of the cab by the HVAC doors. Unless there's a reason you want to keep the troublesome water control valve. Added to my list. I was hoping something like this would work, as it seems overly complicated as it is. Thank you. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted May 28, 2018 Share Posted May 28, 2018 Make sure you cap the vac line coming out of the firewall if you delete the valve (I used an actual CAP as opposed to a sheet metal screw or a golf tee). Any open vac line on the pass. side will cause the HVAC door switching to default to defrost vents. Link to comment Share on other sites More sharing options...
Michael Buskirk Posted July 11, 2018 Share Posted July 11, 2018 What do you do with the coolant reservoir and associated lines? Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 11, 2018 Share Posted July 11, 2018 53 minutes ago, Michael Buskirk said: What do you do with the coolant reservoir and associated lines? Nothing needs to be done with them, so I don't know what you are asking. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 12, 2018 Share Posted July 12, 2018 23 hours ago, Michael Buskirk said: What do you do with the coolant reservoir and associated lines? Yours is a 90 and there is a different procedure for that. do you have a radiator with a cap on it or only the pressure bottle with a cap? Link to comment Share on other sites More sharing options...
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