Hi all,
I picked up a clean 99 XJ for my Daughter last winter and all was well until recently when it started blowing Luke warm heat only.
I will try to be very specific to rule out any unnecessary speculation.
Her temp gauge was registering fine at the 200deg area.
The heater core hoses both felt pretty warm when engine warmed up.
I replaced her thermostst with the 195 deg "better one" the auto parts store guy recommended which was the (fail safe) one.
After I did that nothing changed with her heat other than the temp gauge sits a bit cooler religiously at 195deg.
I decided to back flush the heater core with a garden hose and I got some nasty brown water out of it and it pretty much cleared up right away and flow was good.
I decided to flush the radiator as well and refilled the whole thing with prestone 50/50 mix.
I ran the system, burped the air.....took a while as the lower hose collapsed on itself during the process but corrected itself once I burped the air out.
I let it warm up and cool several times until I was satisfied that the resevoir no longer needed topped off.
My daughter has since taken several trips on the highway to and from college with it with still Luke warm heat only.
Both heater core hoses are hot when engine is hot so my best guess is something in the dash, possibly a blend door.
I know the later models like mine do not have a heater control valve but I have heard about blend door problems.
I don't know what I'm looking at but I do have a Hanes manual I need to look through to try to locate my blend door and get a grasp on my hvac system.
Just to note that the air volume and movement seems to be working fine and routing through all the proper vents on command, just Luke warm heat.
The only thing that struck me kind of weird is that a couple times when I initially warmed up the vehicle I noticed the vents seemed to blow pretty warm air, almost hot until the vehicle warmed up further then it backed off to Luke warm after a short test drive and would not change from that point forward, even while idling several minutes.
I'm thinking I have some sort of crappy vaccum actuated flap I need to locate and check.
Any thoughts for this 99 XJ, 4.0 auto, 4WD are greatly appreciated.
I picked up a clean 99 XJ for my Daughter last winter and all was well until recently when it started blowing Luke warm heat only.
I will try to be very specific to rule out any unnecessary speculation.
Her temp gauge was registering fine at the 200deg area.
The heater core hoses both felt pretty warm when engine warmed up.
I replaced her thermostst with the 195 deg "better one" the auto parts store guy recommended which was the (fail safe) one.
After I did that nothing changed with her heat other than the temp gauge sits a bit cooler religiously at 195deg.
I decided to back flush the heater core with a garden hose and I got some nasty brown water out of it and it pretty much cleared up right away and flow was good.
I decided to flush the radiator as well and refilled the whole thing with prestone 50/50 mix.
I ran the system, burped the air.....took a while as the lower hose collapsed on itself during the process but corrected itself once I burped the air out.
I let it warm up and cool several times until I was satisfied that the resevoir no longer needed topped off.
My daughter has since taken several trips on the highway to and from college with it with still Luke warm heat only.
Both heater core hoses are hot when engine is hot so my best guess is something in the dash, possibly a blend door.
I know the later models like mine do not have a heater control valve but I have heard about blend door problems.
I don't know what I'm looking at but I do have a Hanes manual I need to look through to try to locate my blend door and get a grasp on my hvac system.
Just to note that the air volume and movement seems to be working fine and routing through all the proper vents on command, just Luke warm heat.
The only thing that struck me kind of weird is that a couple times when I initially warmed up the vehicle I noticed the vents seemed to blow pretty warm air, almost hot until the vehicle warmed up further then it backed off to Luke warm after a short test drive and would not change from that point forward, even while idling several minutes.
I'm thinking I have some sort of crappy vaccum actuated flap I need to locate and check.
Any thoughts for this 99 XJ, 4.0 auto, 4WD are greatly appreciated.