JeepcoMJ Posted October 24, 2007 Share Posted October 24, 2007 my 2.5 4 cylinder 86 xj is running pretty good...there's just one problem with it. the heater doesn't work too well. everything's functional electronically etc., but the heat comes out best when it's at 2700-ish rpm. at idle it puts out cold. now, the head is fine, the head gasket is fine. it's actually bled just fine too. so I'm wondering what the deal is? gunked up heater core? any ideas? Link to comment Share on other sites More sharing options...
jaekl Posted October 24, 2007 Share Posted October 24, 2007 I've lost heat a couple of times on my 86 2.5. First time was clogged radiator. The recent one was the water valve was stuck. Vaccum closes the water valve when the heat is not required. I had vacuum once I fixed the line to the reservoir. However, no vacuum should cause the heat to flow, so I figured it must be stuck. I blew into the valve connection and heard it move, Problem solved. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 24, 2007 Author Share Posted October 24, 2007 hmm... it could have a vac. leak, I know there's probably one or two due to cracked hoses. perhaps it works better at higher rev. because the motor creates more vacuum, so it finally gets some in there. I'll look it over. the rad is close to brand new, t-stat is good, all hoses are good too. Link to comment Share on other sites More sharing options...
jaekl Posted October 24, 2007 Share Posted October 24, 2007 Does the air flow ventsrespond when you redirect? When there is a loss of vacuum, all air goes to defroster and the heat will be on, if everything else is working properly. If everything works including directing the air flow, then it could be a stuck heater valve. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 25, 2007 Author Share Posted October 25, 2007 Does the air flow ventsrespond when you redirect? When there is a loss of vacuum, all air goes to defroster and the heat will be on, if everything else is working properly. If everything works including directing the air flow, then it could be a stuck heater valve. yeah everything works. idk about the air valve tho.. Link to comment Share on other sites More sharing options...
Pete M Posted October 25, 2007 Share Posted October 25, 2007 If the heat improves with higher rpms, then I'd suspect a clogged heater core since the flow pressure increases with rpms. You may get lucky and be able to clean it up by disconnecting the inlet and outlet and then reverse flushing it with a garden hose. Link to comment Share on other sites More sharing options...
90PioSport99 Posted October 25, 2007 Share Posted October 25, 2007 Jeepco, I don't know about your 2.5L but what I'm a fan of doing on 4.0Ls anyway is eliminating that heater valve like on the 97+ XJs. It is one less weak part in the system. Just for kicks whenever you get a chance, would you take a picture of your heater hoses so I could see the routing? I would also lean more towards a clogged heater core, but the valve would be a place to start. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted October 25, 2007 Author Share Posted October 25, 2007 http://photos-d.ak.facebook.com/photos- ... 9_5499.jpg best one I got at the moment...I'll take one tomorrow. Link to comment Share on other sites More sharing options...
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