bobcat 325 G excavator overheating

[Woogers64]

Hello . I have a 325 Excavator that keeps overheating, typically when its hot outside, making it almost unusable. I have replaced the thermostat,Radiator Fan, drive belt , replaced the radiator, radiator cap and coolant . Good flow across the top of radiator Anyone have any ideas what might be wrong with it ? Thank you

 

[foton]

I guess it is possible to have a bad head gasket and having combustion gasses enter the coolant there , could the movement you see in the top of the radiator be combustion gas? maybe do a coolant leak down test to rule it out or worse a cracked block. did the old coolant show signs of contamination?