yeah maybe if you didnt torque them or tightened them,never had an issue with them backing out,you might wanna buy a torque wrench, waterpump bolts are fine,i loctite all my bolts and torque to specs.found out looks to be multiple collapsed lifters, springy is good and no movement is bad,so i guess replacement of lifters is on the agenda...yay......DAMN IT!!! well looks like i either got to sell quite a few parts off the parts car to either replace the lifters or rebuild the 99 head i have sitting in the garage,hmmm