Good idea to tape it to test it. I know mine were clear as I had run water through each and watched as it drained below the car. I could see the water dripping from around the AC under the dash which the glove box removed. When I taped over all the AC/Heater vents and turned the fan on high, it blew out the drain lines, the moldy/dirty water would blow out each side of the transmission underneath. But, this was reoccurring after a week or two. So I taped a plastic tube to the end of an air hose, turned on with about 5-10 lbs of air and blew it into the dash vents. Had all the vents covered with cardboard and taped shut when I did this. Cleared it out and could see that it had blown out under the vehicle. That was last summer. We’ll have to see what it does this summer.

 

This literally just happened to me and I think its a been a source of an issue for years where I had an odor and was like whats that...I was literally washing crap out of various areas of my car where a sludge kind of accumulated at my trunk area trunk and saw a large puddle today at passenger floor. Im going to recreate my issue then apply the TSB...Dammit

 

I had the same problem. In my case it was the air conditioner evaporator drain tube that was clogged. The end is in the midline above the transmission.

 

Someday the British will notice that it rains in England and water causes corrosion.