ok iam new here but looking for a little help i have a 2000 frontier crew cab
4x2 automatic  and its on her third set of head gaskets ( is that normal i
dont drive it hard mostly highway miles)107,000 miles about a month ago i
started getting tell tales signs of a leak, low coolant levels a little
moisture in the oil filer cap so since i was away from home on a trip i put
some stop leak in the radiator it quit using water ok i know bad idea but i
was a long way from home. now  it got me baffeled the coolant level in the
radiator is going down and filling the recovery tank but not taking any water
back in there is no water showing up in the oil and no steam at the exhaust ,
i can drive it for 200 miles non stop and open the radiator cap with no
problem. i have taken to the shop where the third set of gaskets were
installed but they cant find anything wrong so i know i am gona get it back
with the same problem it had when i dropped it of. PLEASE HELP