red heart beat that makes alot of sense caus it kinda sounds like it quits hitting on all cylinders like the puter is doing it and even though i was circulating Im sure that the engine is still trying to burp some air out caus every once in awhile the water tank would start riseing and running over when i killed the engine it went down to nearly empty, also not to mention when the engine was shipped to me the temp sensor was broke off, so i replaced it they had two listed one was 10 bucks the other was 27 bucks the guys at napa said that the 10 dollar one went in the front of the head i hope i got the right one, also this thing did the very same thing the first time i started it and i could not get the water circulating caus my water bottle was mounted a little to low and i did not have the block full of water, although it happende sooner. witch makes sense . it idles with out missing a beat for a long time the boom all of a sudden the starts sputtering and tries to die. but there is no mechanical noise it just sounds like it quits hitten on all 8