I've got an 03 Disco SE7 and when I was vacuming the passenger floor board, I noticed that it was wet. I wasn't able to find the source. Seemed like the water had to come from below. Any suggestions?

 

crawl under your truck. There are 2 rubber nipples. They are your a/c condensate drains. Poke a hanger up there and get ready for mud to hit you.

 

You can also get at these from under the kick board on each side, they're the rubber tube things connecting the tranny tunnel to the console.

 

Thank you very much. I will do that!

 

jsyonker,

Another possible cause could be a broken hose coming to the heating evaporator/radiator.
It happened to my 2000 Discovery. The whole passenger swell was flooded and the truck almost overheats.
The only way to check is by lifting the floor lining on the passenger side and getting underneath the fascia, you will see the aluminum tubes entering the radiator. See if the area around it is damp and check it with the engine running for leaks.
Monitor your water level just in case. If you're leaking water, this could be the cause.

Carlos

 

If it is water, then it is the condensate drain.. The only way for it to be what you are describing is if there is coolant on the floor. There will be a sweet smell, your coolant level will be low, and eventually your truck will run hot. If the heater core or lines are leaking, this needs to be fixed ASAP.