I have a '91 f150 with a 351w. The truck practically drinks coolant but there are no signs of leaks anywhere. The oil isnt milky colored and the exhaust doesnt smoke at all. However, when I refill the raidiator with coolant, it bubbles up. Im at a loss and have no idea what to check. Any help would be greatly appreciated as it is my only vehicle. The temp gauge also never shows anything but cold, not sure if that has anything to do with it, but I guess all info helps.

 

Those engines like to blow the little hose that goes from the water pump and the intake.

 

You may have a pinhole leak in the main hose, when the temp goes up the hole expands and the coolent sprays off, maybe onto the exhaust manifold and then burns off. You won't see the leak then.