I have a leak coming from the radiator that is intermittent. I think it is only present during highway driving. Yesterday I wheeled all day and didn't see a drop. The leak is dribbling down the radiator, down the center of the cross member onto the steering damper. Does the cooling system build more pressure during highway driving? Is this why I only see the leak at certain times? I have a new OEM rad ready to go in but I want to makes sure this is the source before I tear it down.