After towing 10,000 lbs trailer for six hours nonstop I noticed a leak coming from a black cylinder (to the right of coolant tank), or a black 3/4" outlet coming from the firewall next to the black cylinder. It looked like water - about one cup leaked out and then stopped. What would it be? The truck is 2006 auto CTD. Air conditioning was not on. I went over some mountains, from dry and hot climate to the coastal wet weather. I'd like to get some education on the subject before taking it to the dealer.

Thanks in advance for the responses.

 

was your defrost on???

 

IF the defrost was on, the AC compressor was running. That's the only other position you will have which turns on the compressor.

Tony