Quote:
Originally Posted by Rubbond
Kevin,
It's precisely to stop the coolant boiling! Otherwise you would have to keep topping up. Many engines are designed to run at about 105 degC, adding to the pressure requirement.
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Maybe modern engines are designed to run at 105 degC, but these old Splodge and Chrysler V8s are not. Someone on here said that the 313/318 engines run at 85-90 degC and the 383/400 engines in the 411 run at about 95-98 degC.
I can see why
some pressurisation is desirable - to keep air out of the system for one and to allow them to go a little bit over their normal running temp.
The 411 has a 13psi radiator cap, which means the water would reach 120 degC before it boils (at sea level). The 407/408 has a 15 psi cap - which means it can exceed it's normal running temp by more than 30% before the coolant boils. That seems rather excessive.
That's using water only - if you add glycol based anti-freeze the boiling point is even higher.