xjoking95

Ok so I've been reading a lot of post about this issue and I've been trying to narrow down the cause. I have flushed the heater, water is clear. I replaced the heater core valve and the thermostat ( did all three today). I am only getting air through my defrost vents and at idle the air is barley warm. When I hold the ram's up the air gets a little warmer but not hot. Does any body have any ideas? I really don't want to take the core out and don't really think it's the core anyway since I get a a little warmth. Maybe the water pump? I also notice I am missing my vacuum ball.

caged

replace your missing vac ball, that should get you heat or air at least coming from the other vents. your selector runs on vacuum.

as for little to no heat, and your engine temp is where it should be, i would look into the water pump. i have seen these before where they look perfectly fine externally with no leaking from the weeping hole, but when removed, there are no blades left on the impeller.

did you check both heater hoses to see if they are both hot? when you flushed, was it a good flow of water?

i just went through this myself, replaced everything but the heater core and i seem to have pretty good heat again.

xjoking95

I'll check out that water pump and look for a ball. All the hoses are hot and flow was good.

JandDGreens

It sounds to me you are having the same issue we had with my sons' 95" XJ. I flush his system also to no avail. Then I noticed that when I slid the heat lever over, the arm that controls the blend door was stripped leaving it only on the cold setting. Luckily we had the control cable from his old XJ swapped it in and now have control of the blend doors and plenty of heat now.

I would move the control arm and look at the little metal lever down by the blend door and see if it moves with the controls. Hope this helps.

JandDGreens

The other thing that could be part of the problem, is leaks in the vacuum lines that control the flow through the heater core if you still have that diverter valve. Also as the previous poster mentioned the vacuum line going down to that ball in the bumper controls the heat/vent/defrost. When I bought my 91' the P.O. installed a winch bumper and ditch the ball that builds pressure that adjusts vents, Trace all your vacuum lines for cracks. These are relatively cheap problems to fix, Unless you have to replace the bend doors but even that would not break the bank.

xjoking95

The adjuster lever works just fine, I watched it move in and out. Where is the diverter valve? I got the water pump off and water runs through it fine so could it still be the pump?

Turbo X_J

If both hoses going to the heater core are hot, and the selector cable controls the lever on the HVAC box, the problem is with the internal temperature blend door.

xjoking95

Ok where is the internal blend door and any ideas on where I could find one other than a junk yard? The only ones I can find and the videos I can find are for the grand cherokee.

caged

blend door is located inside the heater box which houses the heater core.
you would have to remove the dash to access the heater box. you may as well replace the heater core if you have to go that far.

cruiser54

Here. It's cable operated.

cruiser54

Eliminate the Heater Control Valve.

HCV Removal

Well, you guys ponder all you want.

The heat is controlled by the blend air door. I've eliminated at least 10 of them here in Arizona and my AC always works perfectly.

Let's not have this thread turn into one of those where folks think theory and conjecture trumps actual field experience which has been proven time and time again, by numerous different people.

It flat works. Period.

I've already stated the other benefits of keeping coolant flowing versus being stagnant in the heater core and the dangers/disastrous results of having one fail unexpectedly whether you're poking around the engine bay or driving down the highway or trail.


One thing you may want to consider, is removing/eliminating the heater control valve, if you haven't already. '96 down have the HCV, '97 up the Factory eliminated it.

During the warm months, with a HCV, (temp lever/**** never moved off cold) coolant sits and stagnates inside the heater core.....There's no fresh coolant/corrosion protection circulation through the heater core.

With the HCV removed/eliminated, coolant/corrosion protection flows through the heater core constantly when the motor is running, regardless of where the temp lever/**** is set.

Also, you don't have to remember to turn/slide the heat lever/**** when flushing/re-filling the cooling system because coolant is flowing to/through the heater core when the motor is running and the HCV is absent.

Be sure to plug/cap the small vacuum hose when eliminating the HCV.

xjoking95

Thanks for the help I'll make my way to heater core then. Just to make sure I'm understanding, eliminating the HCV won't get me heat it'll just help keep my heater core in stay in good condition?

cruiser54

HCV Removal

Well, you guys ponder all you want.

The heat is controlled by the blend air door. I've eliminated at least 10 of them here in Arizona and my AC always works perfectly.

Let's not have this thread turn into one of those where folks think theory and conjecture trumps actual field experience which has been proven time and time again, by numerous different people.

JandDGreens

I still have my valve on my XJ. But I think your right, it is unnecessary.

JandDGreens

Hey I just looked on Ebay and couldn't find a blend door that would be a direct fit I thought you could find it there. Let me know if you can't find one near you. I will get the one out my son's old 94 XJ it should be the right one. I am planning on making a trailer out of it and will be tearing the whole dash out of it in about 10 days.
P.M. me if you are in need of it.