just want to confirm what Servitek have done with my car to test my overheating problem.

- To check if my HG is OK
What they did is they get a small mineral water bottle with water inside then disconnect the smallpipe coming from my radiator to my reservoir and put the end of it to inside the bottle. They rev the engine and told me that if bubble will come out or any pressure coming from theradiator then my HG is gone. IS IT TRUE? Is their way of checking Bad HG accurate?

- They also use a tester to check my engine temp and in a certain temp my radiator fan should switch on. This is how they check if my thermoswitch is ok.

- I told them to check my thermostat, and what they did is hold the lower and upper radiator host. The mechanic told me that my thermostat is OK since my lower and upper rad host are both HOT.