I bought a 54 TEA 20 three years ago and discovered the same problen shortly there after. Following the comments that I recieved here, using sealant in the rad, checking for cracks in the block,using cardboard to check the drippings after removing the oil pan to see where the coolant was coming from, lead me to the actual problem which was a botched, quick fix, job on the cylinder sleeves where someone used scilicone as a gasket instead of the original copper. Fortunately there was no damage to the motor that I could find. After replacing the sleeve gaskets,main and rod bearings, front and rear crank seals and all gaskets Fergie is working just fine. Thanks to Easy Tractor, Brantford Ontario. Hope your problem is not too serious.