Red 1989 MJ Posted October 6, 2010 Share Posted October 6, 2010 Take a 20 min. ride with my 89 truck yesterday. Put the heater on, blowing hot air. After driving a couple of minute the air stop coming out, I release the gaz pedal and the air come back. Do you have any suggestion were to begin my search? :dunce: Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 6, 2010 Share Posted October 6, 2010 Check all the vac lines along the passenger side fender and under the battery to the vac cannister (reservoir) behind the bumper. Sounds like you have a small leak, most likely a cracked/corrded vac hose. As in, some vac is working there when you are off the gas, but not enough under load (a little leaking out). Very common for those hoses to have a break. Replace the offending hose. Link to comment Share on other sites More sharing options...
Red 1989 MJ Posted October 6, 2010 Author Share Posted October 6, 2010 Is the cannister on all model ? :brows: My Comanche don't have any option. (no Cruise, no A/C) Link to comment Share on other sites More sharing options...
ParadiseMJ Posted October 6, 2010 Share Posted October 6, 2010 Is the cannister on all model ? :brows: My Comanche don't have any option. (no Cruise, no A/C) I believe they all came with the reservoir to at least run the HVAC system. You could just have a ball, my MJ does, but mine also has A/C. Still needs the vac res to open/close the doors. Previous owner may have removed it!!? It's IN the front bumper. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 7, 2010 Share Posted October 7, 2010 Is the cannister on all model ? :brows: My Comanche don't have any option. (no Cruise, no A/C) I believe they all came with the reservoir to at least run the HVAC system. You could just have a ball, my MJ does, but mine also has A/C. Still needs the vac res to open/close the doors. Previous owner may have removed it!!? It's IN the front bumper. I have the same problem, vacuum lines look good on mine. Someone said that canister can go bad, too....are they still available?? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 7, 2010 Share Posted October 7, 2010 They can go bad, but it's usually the internal check valve that sticks. Any vacuum canister will work, and why the XJ/MJ engineers put the damn thing behind the front bumper I'll never understand. I mounted a new one from a Porsche inside the engine bay and got rid of all that leak-prone vacuum hose. Here's the writeup: http://www.comancheclub.com/forums/viewtopic.php?f=9&t=17120&hilit=vacuum Link to comment Share on other sites More sharing options...
Red 1989 MJ Posted October 8, 2010 Author Share Posted October 8, 2010 Thanks guys :wavey: Link to comment Share on other sites More sharing options...
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