dex-cool leak venture 2000

There is a cylinder about 1 1/2 to 2 inches in diameter and about 4-5 inches long with two water hoses hooked to it and an electrical connector. it is located below the coolant resivoir and slightly toward the rear on the driver side of the engine of my 2000 venture and I am not sure what this is? Can anyone tell me what part this is as it appears to be my leak?