texasdave

Thanks in advance to all the folks who post amazing tips and help on this forum. I have been a long time listener, first time caller so to speak...

I'm pretty handy and have done a lot of maintenance to my 01' XJ, but this issue is still stumping me. It might involve the heater core, so it is way down on my list of other issues since I really don't feel like going through the ordeal of pulling the core out if I didn't have to... fat chance but I thought I'd try... My symptoms sound like other heater core issues, but I wanted one last confirmation if anyone cares to offer a second opinion:

Symptom - AC is off, blower is off, temp is set to cold, or hot, doesn't matter. In this situation I'm guessing that there shouldn't be ANY forced air coming into the cabin.

However I am getting a noticeable amount of air at:

- the front window defrost vent

- the driver / passenger front dash fixed position defrost vent (above the movable AC vents near the doors)

- and the foot vents below the dash

The air increases as I increase speed, and it definitely has an odor. The volume of air at highway speed is almost as powerful as the blower setting on the lowest position, let's call it 1. The rest of the vents have zero air coming from them.

Is this normal for late model XJ's to have residual engine air flowing into the cabin? This is my 2nd XJ. My other one didn't do this.

Could this be a leak in the plenum?

Blend door issue? I'm lost and hoping y'all have some sage advice.

thanks!

dave

E4_Mafia

I too denied that I had a heater core leak for a very long time in my 2000 XJ. I lost a small amount of coolant every month, the carpets were never soggy the windows would fog up a bit.
Let me save you some time. It's the heater core man it's not impossible to change it's time consuming but honestly not that challenging
Good luck man

BillyBoy

Really wasn't that bad.

E4_Mafia

jatoxico

Does it smell like antifreeze? Wonder if your AC condensation drain is clogged. Its a tube that comes out through the firewall on the psg side, down pretty low.Run a wire through it.

texasdave

Thanks guys! I appreciate the advice, and will be collecting myself mentally for ripping out my dash...

So, the smell is definitely antifreeze, and I've added antifreeze to the reservoir over the past few months from time to time - no question that it's got a leak, but my other head scratcher is why does latent warm / hot air continue to flow through the vents (and increase in volume at speed) even though the system is presumably OFF according to all the dials I can twiddle... The blower motor resistor is fine, it's working as it should on all settings (relatively new too), so I feel I've ruled that out as a possible problem.

Would a vent door be stuck partially "open" to allow the free air to flow in across the engine into the vent system? Does your XJ always have air coming into the cabin no matter what?

thanks!!
d

CCKen

"Symptom - AC is off, blower is off, temp is set to cold, or hot, doesn't matter. In this situation I'm guessing that there shouldn't be ANY forced air coming into the cabin.

However I am getting a noticeable amount of air at:

- the front window defrost vent

- the driver / passenger front dash fixed position defrost vent (above the movable AC vents near the doors)

- and the foot vents below the dash

The air increases as I increase speed, and it definitely has an odor. The volume of air at highway speed is almost as powerful as the blower setting on the lowest position, let's call it 1. The rest of the vents have zero air coming from them.

Is this normal for late model XJ's to have residual engine air flowing into the cabin? This is my 2nd XJ. My other one didn't do this.

Could this be a leak in the plenum?"


~~~~~~~~~~~

While this was happening did you have the Mode Selector OFF?


With the Mode Selector OFF, the Recirculation Air Door should be open to the cabin and no ram air entering the cabin from the outside.


The Recirc Air Door needs vacuum to open. If there is a vacuum loss to the HVAC system the Recirc Air Door will close, allowing outside air in.


Check this:


Roll the glove box down so you can see the Recirc Air Door and its actuator arm (see pic),


Select fan speed 1,


Run the engine for vacuum,


Run the Mode Selector through all of its positions, noting what the Recirc Air Door does when MAX AC and OFF are selected. You should see the Recirc Air Door move open/close. If it doesn't move the vacuum source to the Mode Selector from the engine has been removed.


Do this and get back.


View of Recirc Air Door opening through the rolled down glove box:





Mode Selector vacuum positions: