Tell tale signs will be heavy green slime from IC to intake manifolds. If it's a total failure, your SRT will let you know, via codes; P0105-MAP & P0507-IAT sensors. Your symptoms may vary, but mine had obvious power/performance loss since both sensors mentioned were enveloped in green slime! Got down to hard start-no power to drive. CEL popped up revealing MAP & IAT sensors. I was aware of slight IC leakage when I installed recent NW manifolds. It wasn't long until complete blowout occurred.
The color of the slime will be the color of your coolant so not neccessarily green.