This week, we went to change the cracked cooling hoses on a Frogeye only to find a very rusty thermostat and an amazing accumulation of rust in the lower hose. This is from running the car on water only, which is what we drained from inside the engine (rusty water).
Freeze risk aside, regular old green antifreeze has anti-corrosion properties, and if you don’t use it, your cooling system will sprout the rust blossoms you see here.
Nuff said.
