Born in the footballing hotbed of
West Wallsend, New South Wales, Coolahan began his playing career with
West Wallsend before crossing to
Adamstown Rosebud in 1929. He returned to West Wallsend in 1931 though he only stayed one season before crossing to Speers Point. After another stint with West Wallsend in 1933 and 1934, he moved to Adamstown. At Adamstown he played until the end of the 1942 season. He played his final season of senior football in 1943 for
Lake Macquarie. ==International career==