Bad radiator cap will cause that, and will also cause overheating.
That said, how many miles on the engine, and why head gaskets?
Did it fail a coolant combustion gas check?
96 T/A, Black/Graphite Leather, T-Tops, 6 speed, 10 speaker Delco/Bose "Monsoon"
Original owner, 217k miles and counting.
Total engine rebuild at 187,020 miles. AIR delete, bored .030 over.
Comp cams Xtreme Energy LT1 266HR-14 street cam and springs.
Custom leather interior at 190k miles. Total repaint 193k Miles
Last edited by NavyVet; 08-17-2015 at 05:58 PM.