@perrobravo Did you block airflow to the radiator when you did the TeeKay test? It helps to bring it up to temperature quickly and sometimes you won't be pushing coolant until things get up to operating temperature and are under a bit of a load/stress. Your symptoms suggest combustion gas issue mate, which can be due to numerous reasons: head and block mating surfaces, improper head bolt torquing, using coolant instead of straight water for the first 1,000km, using any type of HG sealant Etc...