Advice on finding a leak...

[Brock Samson]

My motor home (Dodge B van Chassis) has a water leak that appears in the pedal area of the floor when parked downhill and behind the drivers' front seat when facing uphill... there seems to be no water dripping from above - the only moisture is in the carpet and is approx a cup of water or so in a eight inch square,.. my other vans had no carpeting but this one has wall to wall carpeting that extends up the walls to the roof so getting it up to check/fix is pretty much impossible without removing a lot of bolted in stuff... or ripping out that section of carpet..
Does anyone have any ideas how to trouble shoot this problem?.. 

[Steve P.]

The puddle changing places may simply be due to a channel in the floor sheet metal. Does the puddle have any smell to it?? Are you losing any coolant?? I am thinking heater core leak...  If it's coolant it will have a sweet smell.

I would do a visual of the area in question. Check for missing calking or cracks in the roof where the raised top meets the steel panels. 

Does your camper have roof A/C?? It may be a plugged drain tube or maybe the tube has been pulled out of place or a screw put through it.

If you still have not found it you can do a water search on it.  Start from underneath the truck with a garden hose. Small areas and go from the bottom up checking frequently inside. Even better to have someone inside continuously checking the entire area.

Work your way up to the winshield wiper pivots. A good flashlight will really help with dripping water.

The big mistake people make when doing a water test is starting up high or moving up too fast. Sometimes it takes some puddling on the outside before it makes it's way inside. 

Hope you find it and it's something easy. It would suck to have to remove the interior..