I have a 2001 grand cherokee and have water in frt passenger floor instaalled right handl elbow and tube.still no water fr drain.

Underneath by the gearbox but if the front carpet is wet up the top under the dash it will be your heater matrix leaking

floor of what garage, or passengers foot.
ill now guess, foot.
there is no need to do that, just clean the drain tube, and put it back.
make sure it drains, to the garage floor and its fixed.
its just a drain, no need to take dash apart and 10 hrs labor,
not at all.

for sure all generic answers here are wrong. for all grand Cherokees. 93 to 2010
posters jeep is 2001 WJ , only WJ 1999- to 2004 (USA only) are correct. RHD cars are not the same. UK

we all know why, (clogs happen evap drain clogged)
we all know it must be cleaned. (just like clogged kitchen drain )_
what is not told , "your hands can not reach the spot. transmission block you, and CATs)
the drain tube on my 2008 wrangler(2dr) is in plane site just above starter. so is easy
the wJ and WK jeeps are not easy, and WK is the hardest of all made. blocking shield under car.(above right side of transmission NAG1.

THE FSM LIEs IS HERE. Jeep sells the cleaner kit and the TSB covers how in 24 long pages.
but step 1 below fails; (way to go JEEP,. FCA) #2 is CAT crossover,3.7L

the A/C drain is stopped up, causing water to fill the "heater box" and spill into the cabin, right into the passenger floor.

The drain would be in the engine compartment and would look something like a rubber elbow sticking out of the firewall. You could try snaking something flexible in there or I personally have used a blow gun and compressed air.

bad heater core, leaking into pass. side floor?

It is the condensation from the ac,the drain is stopped up,it is located under the hood,under the ac lines that go into the firewall,look directly below them,it will be there,and there is a elbow boot on the drain,remove it,and blow air into the drain,and if it clears it out,the water will pour out like a water fall,if this was at all helpful,please rate,thank you.

evaporator drain is plugged... Look at the bottom of the firewall on the passenger side... should see a rubber tube (Short, only an inch or so long) coming out... need to squeeze it and see if anything is plugging it.

You problem is probably a blocked or resricted drain tube that allows the condensation to leave the vehicle

keeper of fire here is mostly right...however, on my 96 grand cherokee with the 5.3 liter V8, there is a slight design flaw...the evaporator tube is actually IN the framing...
this baffled me for a time, until a local jeep mechanic told me that this was regular in a jeep zj, and that all i had to do was pull back the carpet on the psg side and drill (yes drill) a hole into the plastic so you can stick the wire in, or an air hose and unclog your tube from there...then you silicone it back up and tada!! be sure however that before you drill willy nilly that you are actually drilling in the right spot, this can kinda be found by following what bit of hose is visable and seeing where it disapears into the floor...and its a little black plastic circle that you will drill into...hope this helps!