Hi guys i went with a cheaper option of getting a used stirrup pump,it seems to be in good order,but what do i know now,when it gets to about 250 bar,i turn the bottom screw to let the excess air out,as i have never used this before it sounds like a bit of air is coming out,not 3000 psi but never the less it a sudden shhhh noise,is it meant to do this or am i doing something wrong please help me.