Heater box gasket(s) question

I have been having a few issues with water on the passenger side floor board of my 2000 xj. through searches I have got all my fixes either done, or planned out. Thanks atriot:

One question, referring to the Foam gaskets that are on the heater box sealing it from the cowl and firewall. Are those designed to stop water from coming in. Conceptually speaking, if the factory wanted to keep water out as well as air, wouldn't they have used a rubber gasket? not one made from foam? This would lead me to think that a water leak at the lower foam seal (on the firewall) is just not suppose to get wet. making leak prevention more of preventing the water from getting there in the 1st place.?.?

My contradicting theory is that if the foam gasket is designed to stop air, by default it should be stopping water too.:confused1

I thought about using sealant to seal it up, but I want to wrap my head around this before I throw something at the problem that is not "factory" application wise. Im not looking to rip the whole dash out to replace a couple foam gaskets, as my heater core and evap are in good shape...

Thoughts, Opinions?

Thanks
Bronze

? Nothing? I was hoping to get started on the last leak here In the next few days...

Thanks
Bronze.

Have you checked the AC drain line? If they plug, you'll get water on the pass side floor.

-Ron

oh yeah, ive been through the whole shpeel. Ive updated my build thread on here im am on all this. its at the bottom of page 3. I Can visually see the water/mud coming in right off of the foam gasket looking up and under the dash

http://www.naxja.org/forum/showthread.php?t=1081015&page=3

Bronze.

Cool!

Foam is used by car manufactures for tons of things you would think that rubber would be involved with, for example: between an axle retainer and the housing.

They are not trying to keep a total submersion under control, they just want to seal the box to the firewall to maximize the airflow to the cabin, seal off the fan, and prevent the small amount of water that usually gets to that area, out.

The foam seal is to insulate and seal the air coming through the system. If you're leaking coolant (or just water) in the cabin, it's either the heater core leaking, the A/C drain line is clogged or water leaking in from the cowl.

Foam rubber is NOT used to seal out water, coolant or oil.

Well... The late model XJ's, some of them like mine for instance, leak water at the HVAC box and cowl junction. The foam seal fails and the only way to resolve the issue is to remove and replace the seal which is, as I understand it, a Dealer Only Item.

Pf course, to do so means that the A/C has to be professionally drained and the lines sealed off prior to the repair of the gasket itself. There have been several threads on about this very issue.

To be honest, I attempted an external repair in the cowl using silicon sealant and foam. It worked for two summers and then broke down allowing water back in.

To get at the air intake, you have to cut your way into the cowl. This means that the cowl panel grill must be removed to gain access to the sheet metal. Once the patch is in place, that sheet metal needs to be welded back into place.

Like I said, I tried this and it worked for a couple of years. I have no idea what the part costs but I do believe that part number is 4897 639AA. Leastways that is what my parts manual claims...

I "proved" this was my leak point simply by dumping water into the air intake on the Driver's side of the cowl grill. And yes, I had already verified that the cowl drain was open, not pugged.