Minuit Posted April 6, 2015 Share Posted April 6, 2015 So, the MJ is about an afternoon from being roadworthy, if all goes well. However, it turns out that a friend of mine accidentally broke the plastic heater control valve in the process of helping me replace heater hoses. Should I bother to replace it or just bypass it, and if I do bypass it, will it make any real difference? Link to comment Share on other sites More sharing options...
91Pioneer Posted April 6, 2015 Share Posted April 6, 2015 Bypass it and don't worry about it. I deleted mine when I changed hoses, but I got one-piece 97+ XJ hoses to clean things up. Plug off the vacuum line with a bolt or something. Link to comment Share on other sites More sharing options...
Tommy Posted April 6, 2015 Share Posted April 6, 2015 I bypassed mine and blocked off the vacuum as mentioned above. I'm happy with it Link to comment Share on other sites More sharing options...
wvzj Posted April 7, 2015 Share Posted April 7, 2015 I bypassed mine with no ill effects Link to comment Share on other sites More sharing options...
metrictonner Posted April 8, 2015 Share Posted April 8, 2015 You can get a new one already attached to the necessary hoses. When the core pops its cork its nice to have this thing working to prevent unloading the coolant in you MJ...especially when you are out in the middle of nowhere. Link to comment Share on other sites More sharing options...
Megadan Posted April 8, 2015 Share Posted April 8, 2015 Mine was already bypassed when I bought the truck. About the only thing different is that if I drive with the HVAC set to heat, some hot air will come through the vents. I slide it to cold, and no problem. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 11, 2015 Share Posted April 11, 2015 Ditch that plastic piece of crap. Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 11, 2015 Share Posted April 11, 2015 mine broke too so I just added a classic style turn on off valve. So winter comes and I open up the flow, spring hits like now I close it off. I just plugged the vacuum line to it. Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted April 12, 2015 Share Posted April 12, 2015 You can get a new one already attached to the necessary hoses. When the core pops its cork its nice to have this thing working to prevent unloading the coolant in you MJ...especially when you are out in the middle of nowhere. This is the one and only good i have heard for keeping the heater valve. That being said i have looong since deleted mine and havent looked back. A/C and heat both still work excellent. Besides after 97 the heater valve was axed all together. Snag a set of 97+ cherokee heater hoses and the deleting process is a snap. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 12, 2015 Share Posted April 12, 2015 This guy from Arizona uses no HCVs on any of his rigs. Does that tell you something? Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 12, 2015 Share Posted April 12, 2015 yea you lucky Cruiser, here in North East Texas it can be 25 or 30 degrees and I still need to drive around and feed. I still need to go around and fix fences. So I need my heater going good. I would hate to be 40 acres in back fixing fence and need to get warm hands with not heater lol Link to comment Share on other sites More sharing options...
cruiser54 Posted April 12, 2015 Share Posted April 12, 2015 yea you lucky Cruiser, here in North East Texas it can be 25 or 30 degrees and I still need to drive around and feed. I still need to go around and fix fences. So I need my heater going good. I would hate to be 40 acres in back fixing fence and need to get warm hands with not heater lol Same here. Gets to 0*F. What's your point? Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 12, 2015 Share Posted April 12, 2015 So your ok with cold that is fine. and you don't mind the cold that is fine too. I like it warm that is my point :) Link to comment Share on other sites More sharing options...
cruiser54 Posted April 12, 2015 Share Posted April 12, 2015 What????? You're okay with telling me this doesn't work when I've done it numerous times? Everything works fine. The heat is controlled by a blend air door, not that valve. You must have missed some important fact in a post along the way. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 12, 2015 Share Posted April 12, 2015 I think the idea behind the valve is to keep the heat out of the dash as so it would not compete with the AC. My valve will go to valve heaven too when I install the new engine. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 12, 2015 Share Posted April 12, 2015 I think the idea behind the valve is to keep the heat out of the dash as so it would not complete with the AC. My valve will go to valve heaven too when I install the new engine. Correct. It was a redundancy in engineering that was unnecessary. That said, I live in Arizona and have no ill effects regarding cabin heat in the summer. As long as your blend air door is adjusted properly. .That takes about 22 seconds to test and adjust. Link to comment Share on other sites More sharing options...
87Warrior Posted April 13, 2015 Share Posted April 13, 2015 This winter my '86 could cook me out of the cab at -10°. The silly heater control valve has been missing for awhile. Sure didn't notice any extra heat coming in the cab a week ago when it was 90° either. A failed heater control valve is why it went went in the trash. On a cold day last year I took the truck for a 2hr drive. 1hr into the drive my heat stopped working. At a rest area I determined the vacuum diaphragm on the valve failed cutting the flow of hot coolant to my heater core. I plugged the vacuum line to the valve to eliminate the vacuum leak and dealt with the cold since I couldn't figure out a good way to wire the valve open for the rest of my trip. Luckily the sun was out. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 13, 2015 Share Posted April 13, 2015 This winter my '86 could cook me out of the cab at -10°. The silly heater control valve has been missing for awhile. Sure didn't notice any extra heat coming in the cab a week ago when it was 90° either. A failed heater control valve is why it went went in the trash. On a cold day last year I took the truck for a 2hr drive. 1hr into the drive my heat stopped working. At a rest area I determined the vacuum diaphragm on the valve failed cutting the flow of hot coolant to my heater core. I plugged the vacuum line to the valve to eliminate the vacuum leak and dealt with the cold since I couldn't figure out a good way to wire the valve open for the rest of my trip. Luckily the sun was out. Interesting. Exactly what I would expect from someone who thinks logically, deals with the facts, and takes action........ Link to comment Share on other sites More sharing options...
Rockfrog Posted April 16, 2015 Share Posted April 16, 2015 Mine was already bypassed when I bought the truck. About the only thing different is that if I drive with the HVAC set to heat, some hot air will come through the vents. I slide it to cold, and no problem.This is because you have to slide the selector lever to "OFF" for the fan to stop. Otherwise it runs on low with the speed switch down. The valve was eliminated in later models as unessecary. I eliminated the valve in my 1988 MJ during my cooling system rebuild 2yrs ago (original rad was literally crumbling). Just copied the layout of my 2000 XJ since the water pump and radiator came from it. Just used two lengths of 5/8" hose, did the same on my XJ, both work flawlessly just like they should. Heater works great when I want it to, and does nothing when I don't want it to. Only problem now is I only get flow I defrost, but that's usually where I leave it anyway. 5 Min's down the road the cab is toasty enough to warm my toes ... Eventually I'll dive into the dash and sort it out. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 16, 2015 Share Posted April 16, 2015 Mine was already bypassed when I bought the truck. About the only thing different is that if I drive with the HVAC set to heat, some hot air will come through the vents. I slide it to cold, and no problem.This is because you have to slide the selector lever to "OFF" for the fan to stop. Otherwise it runs on low with the speed switch down.The valve was eliminated in later models as unessecary. I eliminated the valve in my 1988 MJ during my cooling system rebuild 2yrs ago (original rad was literally crumbling). Just copied the layout of my 2000 XJ since the water pump and radiator came from it. Just used two lengths of 5/8" hose, did the same on my XJ, both work flawlessly just like they should. Heater works great when I want it to, and does nothing when I don't want it to. Only problem now is I only get flow I defrost, but that's usually where I leave it anyway. 5 Min's down the road the cab is toasty enough to warm my toes ... Eventually I'll dive into the dash and sort it out. Dash? It's in the bumper........ Link to comment Share on other sites More sharing options...
Rockfrog Posted April 16, 2015 Share Posted April 16, 2015 ??? The blend door is in the bumper? News to me ... Have you been hanging out with mister triangle gasket guy? Or are we having an app issue and somehow got the vacuum reservoir thread crossed? Honestly, now I'm confused (although it's not so unusual) ... My phone has been acting up the last day. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 16, 2015 Share Posted April 16, 2015 ??? The blend door is in the bumper? News to me ... Have you been hanging out with mister triangle gasket guy? Or are we having an app issue and somehow got the vacuum reservoir thread crossed? Honestly, now I'm confused (although it's not so unusual) ... My phone has been acting up the last day. That's hilarious!! If the vac rezzy is FUBAR or the lines to it are the same, the vents will default to Defrost. And I know you have some new triangle gaskets you're holding out on. On the top shelf in your garage next to your tin foil hat. Link to comment Share on other sites More sharing options...
Rockfrog Posted April 16, 2015 Share Posted April 16, 2015 Man, i make some of the best tinfoil hats, all piratey like, with cool coat hanger anti brain-melter ears amd all. My thoughts are my own ... so are my cornered stock of triangle gaskets. I replace them annually. Actually, my reservoir (which is actually relocated to the inner fender in front of the fan) is good and the vacuum lines in the engine bay are good. The vacuum harness and actuator inside the cab ... not so sure about. And from the mess the PO made of the dash harness, fuse panel, and radio install ... pretty sure my problem is behind the dash. Either it's come apart or something stopped doing stuff ... one day I'll deal with it. Likely when I replace the engine (1990 -C101 delete and DRL's) and dash (1988 XJ in mint shape) harnesses ... might as well make it painful. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 16, 2015 Share Posted April 16, 2015 Sometimes the vacuum harness doesn't seal completely on the back of the heater control assembly. Link to comment Share on other sites More sharing options...
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