If the head gasket fails there is plenty of combustion pressure to force coolant out. Many times the coolant tank will split open before the cap can relieve pressure. In your zero pressure system you have replaced the stock cap with something else? As long as there is a water pump present there is really no such thing as a zero pressure system, more like a low pressure system. Greg F

Related note - is the evans coolant safe to use? We looked at it and found it to be very slippery (more so than normal AF) and also flammable. I know that NHRA says it's approved, but what about NASA or SCCA?

Slippery enough in my car that it leaked out of hose clamped connections where water/water wetter stayed dry.

Anyone have anything official on this? Would love to run it, but took it out for safety concerns.

Matt