Nah, been doing it a long time. Toyota even puts one in theirs. I don't do it much anymore but I always warm the engine until coolant circulates and then top it off if I've had the coolant out.
HTJ---they drill a 3/16 hole in the flange of the thermostat to allow coolant flow without the stat being opened--a bypass kinda sorta--jb's answer is how i had been taught--i did find a lot of forum action on it from years past--some yeas and some nays--i tend towards the yea side--anything to alleviate the burps
Makes sense.... I always do like JB said...let it warm then top off. If I have the Tstat out, I pour some in before installing the Tstat... guess the hole wouldn't be a problem. I've seen some now that I think of it, but never paid any attention. Thanks
Those old AMC Eagles used to be the worst. They would always blow half the coolant back out when they burped. I had a big funnel I could cram into the filler neck to catch it. Then I figured out to put a flushing T in the heater hose and let the air out there as I filled it without the engine running and that worked pretty good too.