part ID question/help

[jonathan-m]

Sorry, I know this will sound a bit silly, but I am still in the process of learning all of the parts and functions of an engine and I am not at all familiar with this one. Today while I had my 66 out I noticed that the big black box in the left corner of the engine-bay started leaking lots of fluid after I parked the truck ( I had driven about an hour, and it was a very hot day). My engine temp gauge doesn't work, but I thought that maybe the leaking had to do with the engine getting too hot. The only reason I thought to check it was that I could smell a faint odd smell in the cab after I parked it. Can anyone tell me what that box is, and what sort of fluid would leak out of it? Is this a big time problem, something I need to work out right away (this truck's my daily driver). Thanks guys!

Jon