I continue to get bubbles and foam in the radiator. there so far does not seem to be oil in the coolant or coolant in the oil. I pulled the plugs and none seem to be cleaner than the rest from water cleaning them. the exhaust gas test in the radiator is negative. compression in #1 is 115 #2 is 95 #3 is 98 and #4 is 120. it seems a bad head gasket between #2 and 3. I owned the tractor about 5 years it has not been worked or over heated. I tested the coolant which was new at that time and is good to negative 45. what next pull the head to do a visual inspection? looking for advice from you guys out there. thanks again. joel