Now, since I did this ATF change (full flush) while I had to remove the radiator anyway, but not the A/C radiator (to swap the timing chains, etc.) I had had both pipes (from and to the transmission) removed from the radiator anyway. I removed the ATF from the transmission (release plug in the pan), which was about 5L, then I put the plug back on. Then - and that is new: I used my "air pressure gun" and I blew CAREFULLY (I did not pull the trigger completely and I intentionally let a bit of airp