Alright so I thought I had fixed my passenger water leak by sealing around the blower motor in the firewall. However I found my floormats to be wet again. This launched a very long leak detection process, agaiun.

Here are my findings:

I took the cowl cover off and flooded the cowl for MINUTES with water getting 360 degrees around the air intake (without letting it go over the lip). The drains work great and I found no water dripping inside.

The blower motor still had some drips when sprayed directly, so I completely sealed off the blower motor from the firewall in order to rule it out (3M HVAC tape). I can now spray directly at it in my engine bay and have no issues.

The foam surround on where the hoses enter the evaporator core is toast and water can get in there, but with the hood closed water is not reaching that area. I did the windshield soapy water test with an air compressor and found no leaks. Applying water to the antenna does nothing.

At this point I thought my leak was fixed, but then I found the real leak.

I decided to turn on the fan to see if it changed anything and water began dripping out of the heater core housing (which as far as I know is what the large plastic apparatus is directly above the passenger foot well). It was coming out of multiple places but it was obvious that it was just pooled inside.

So leaving the fan running, I started adding water to different areas of the Jeep and seeing what made water come out. This included flooding the cowling, spraying the hose at the firewall in the engine bay, spraying the windshield, etc.. After this I started very careful testing with a waterbottle to be more precise with the hose, the only place that made the heater box drip was between the windshield and the cowling cover. Here is a picture of the area circled that caused water to leak.




I'm really perplexed because I don't know what is here. My windshield passed by soapy water/compressed air test, flooding the cowling does nothing... What else is right here that could be allowing water into the heater core?


Any help is greatly appreciated.

 

Have you been running the AC?

 

Yep. AC drain is unclogged and draining well.

Like I was saying, I can make this happen on command by pouring water where I circled in the picture. So I think AC can be ruled out.

 

Probably got a hole at the base of the windshield. Yours wouldnt be the first. Take a peek under the seal and shine a flashlight in there. If you find dirt and pine needles or whatever under the seal, that can trap water, which leads to rust. Check the entire windshield as water may be getting in elsewhere and running along the top or base of the windshield to that spot. Open the door and look for anything suspect along the body. Leaks arent always where you think they are.

 

Is the seal around the windshield glued down? I didn't want to damage it by messing with it. I did test around my entire windshield with soapy water/compressed air and found no leaks. I have a 97XJ if it matters.

 

Hi, I'm sorry to tell you that I ended up paying to a mechanic to solve the issue. The leak was from the gasket that seals the heater box (the section that also have the AC evaporator)
To replace the gasket, the WHOLE dashboard needs to be removed, the guys also removed the passenger seat to clear space. I didn't have the time and space to do it myself, neither the experience doing that before.
I spent $1,800 but that includes the rear seal replaced, oil change and fix the electrical issue behind the gauges (No bus error).
Good news is that was almost 2 years ago, I have no oil and water leaks and the bus error stopped.
The mechanic asked me if I wanted to replace the heater core since everything was dismantled, but it had the original one (I think is copper) in excellent condition, the new one would be a Chinese one and cheaper materials.
That was the only time I took my Cherokee to a mechanic since I have it, in 8 years.
Please see attached the invoice. If you have time and skills, and a place to leave it dismantled for few days, you can do it yourself.

Good luck!

The water was leaking from the cowl section (passenger side) through the gasket that goes in between the air duct inlet (outside air) to the evaporator/heater core section.


Invoice Feb 2021






Heater box location, sorry I couldn't take pictures with all the dashboard removed.







Connector that was lubricated to prevent "No bus" error code.

Main seal gasket location