I'm a department supervisor at one of the local towns as my day job and my best buddy is the chief mechanic at the highway garage. They have a 4 year old Vactor that had started to run extremely hot during our recent heat wave. It has a separate engine to run all the pumps for the Vactor unit and this was the one running hot. My buddy traced the problem to the radiator and found it was only transferring heat at the outer edges of the core using a infrared thermometer. He pulled the aluminum radiator and cut one tank off and found the majority of the core was plugged with what looked like epoxy. It appears someone dumped epoxy into the coolant sometime between now and last summer and it adhered to just the aluminum. The radiator is unique to the machine and cost $3400 to replace! There's probably no way to determine who is responsible for the damage.