How long should a heater core last

.... In a 2000 Cherokee Sport 4.0?

The one in our truck was replaced in 2007-2008.

The heat has sucked since day one when we bought it November 2010. Normally we can just deal with it, but with near record-low temperatures right now, it's not good.

I AM getting a slight coolant smell with the heat/blower motor on, but i think that's because there's a very small leak in the lower radiator hose area, and there's no way to switch between re-circulate/outside air in this thing.

I replaced the t-stat and did a backyard flush on the system myself about 2 months ago. Heat was slightly improved, but i'm not sure if it was real, or if it was just the placebo effect. Also, it was more like 45-50 degrees out.

Sooo.... dead heater core already? Truck does NOT get driven many miles at all.

Junk in the heater box?

when you did the flush are you sure you got all the air out of system. air can be trapped in the heater core also check your heat valve sometimes the valve goes bad and does not open all the way or at all

Ranger50 wrote: Junk in the heater box?

In... liquid? or... Air? I don't really "speak" HVAC at all, which is what makes this so difficult to me.

cutter67 wrote: when you did the flush are you sure you got all the air out of system. air can be trapped in the heater core also check your heat valve sometimes the valve goes bad and does not open all the way or at all

I did install a high-point-fill at the same time, so i'm fairly sure i got the air out of the system, but who knows. Not sure how to get air out if it's in the core...

Also have no idea what or where a heat valve is.

sorry didnt see it was a 2000 they do not have a heater control valve there is always coolant to the core on the later models but there is a door that regulates how much air passes thru the core this is most likely the problem they do break also as stated before "junk" in box and i have seen everything from leaves to mouse houses i would check that

Swank Force One wrote:

Ranger50 wrote: Junk in the heater box?

In... liquid? or... Air? I don't really "speak" HVAC at all, which is what makes this so difficult to me.

like leaves, mouse turds, insulation, etc....

cutter67 wrote: sorry didnt see it was a 2000 they do not have a heater control valve there is always coolant to the core on the later models but there is a door that regulates how much air passes thru the core this is most likely the problem they do break also as stated before "junk" in box and i have seen everything from leaves to mouse houses i would check that

Talk to me like i'm REALLY stupid. (Because i am when it comes to this thing.)

Where is this "door" and how much of a pain in the ass is it to get to?

Is it also a possibility that i've got a "dead spot" on my HVAC control? It's electronic in these things, right? The knob moves too easily for it to be cables.

you are correct it is electric there is a electric door accurator that controls it. and yes its a pain in the ass to get to you will have to remove the dash

Aw man screw electric HVAC door actuators forever, I mean it's like 10 inches from the lever to the door...

Anyways, if you want to make sure it's working, you can try moving the door lever and listening for movement, most cars tend to make a mechanical clacking or banging noise when it moves. On a lot of cars the door actuator happens to be just above the gas pedal or where the dead pedal would be on a RHD car, you might be able to visually check it.

GameboyRMH wrote: Aw man screw electric HVAC door actuators forever, I mean it's like 10 inches from the lever to the door... Anyways, if you want to make sure it's working, you can try moving the door lever and listening for movement, most cars tend to make a mechanical clacking or banging noise when it moves. On a lot of cars the door actuator happens to be just above the gas pedal or where the dead pedal would be on a RHD car, you might be able to visually check it.

And i should hear/see this when i turn the knob from blue to red?

If you keep up on the antifreeze changes, a heater core should last the life of the vehicle. Over time antifreeze becomes corrosive. I've seen 4.0s where you pull the water pump and there's an inch of rusty sludge in the water jacket.

In reply to Swank Force One:

No, you should only hear it when selecting where the air blows (i.e. feet, face, defrost).

Yeah as for checking the "red/blue" thing, some cars use a similar door system to select between the AC evaporator/cool air and heater core, except it has no detents so it moves smoothly and silently. On others, like my 'rolla, the AC evaporator and heater core are always in the path of airflow and moving to the red side simply opens the valve that lets hot coolant into the heater core, so any setting between the extremes literally runs the heat and AC at the same time like that Futurama episode.

The air location thing works fine... so there's no way to tell if the hot cold door works without removing it?

Does the temp controller work to make the air colder? The blend door motor in my Peugeot is broken but it stays on full hot all the time and and the temp knob doesn't make a difference in the temperature.

Hard to tell when the heat isnt working well. When it's 40F outside itll go from cold to lukewarm at best at least.

Check the heater core bypass valve, make sure it's opening fully, the car will have one whether it uses the blend door or "futurama" system.

GameboyRMH wrote: Check the heater core bypass valve, make sure it's opening fully, the car will have one whether it uses the blend door or "futurama" system.

I really don't think there's one on an 00-01 Cherokee, as Cutter67 said earlier. This thing has coolant going to the core 24/7.

I think i'm just completely lost on this whole thing and might have to suck it up and pay a shop.

Looks like it has one:

https://www.youtube.com/watch?v=hKsxuchmJP8

It's vacuum-actuated.

GameboyRMH wrote: Looks like it has one: https://www.youtube.com/watch?v=hKsxuchmJP8 It's vacuum-actuated.

That's not a 2000-2001.

Straight from Cherokeeforum vendor SeriousOffroad:

I'm an XJ guy, but... Late model XJ's don't have a heater control valve, the core is constantly supplied with coolant.

D'oh you're right...that would have to be from a '96 or earlier.

GameboyRMH wrote: D'oh you're right...that would have to be from a '96 or earlier.

And that's why this is hurting my brain..... the core is plainly getting hot coolant like it should. So why is my air not hot?!?!

Maybe it's got the blend door issue like someone said earlier, seems to be somewhat common. I just don't know if i have the time or ambition to take out the dash just to check.

What a stupid design. None of my furrin' cars have ever had any issues with heat. At all. And even if they did, i can GET TO THE GODDAMN THING.

Check this for a diagram of the parts. My current '98 is low on heat with an outside temp lower than 30°F or so. But my previous '98 was good at all temps, though.