machine would overheat when temps above 95 and running cab air. Took thermostat out and seemed to work for a month or so. Now we are overheating and losing water after a very short time. Stat still out and have checked the obvious. no weeping from pump, belt good, can see water circulating inside radiator when cap off. What next? trying to locate a radiator pressure tester for that small cap size now. Machine starts and runs fine but only 10 minutes or so to overheat. Not running cab air. Any clues?