[bumsinflt]

99 Tahoe - 77.0 miles - had slow decrease in antifreeze - noticed overflow tank always empty - slight smell of antifreeze - now hear clicking after truck sets overnight and cold (0 to 20F degrees) sounds like a flat lifter (does this engine have hydraclic lifters?) and goes away after about 5 mile drive - I added a detergent oil for lifters, it reduced noise by 50% but still can hear very faint click after 100 mile drive - I figure I will need to change manifold gaskets (per other threads with similiar anti-freeze problems) - how can I tell what lifter it is and will I be able to fix that lifter at the same time I do the manifold gaskets? Should I do all the lifters since I had problem with one? Is it ok to drive it with a flat lifter? Thanks