Another pressurized reservoir
I have two vehicles with remote pressurized reservoirs, 2007 Silverado and 2020 Frontier and one with the older style overflow reservoir, 2014 Subaru.
In both of the pressurized systems, the top port is to keep air out of the engine, coolant is constantly flowing into this port when the engine is running, along with any air that gets into the system. The hose at the bottom is to return coolant back to the radiator. I would assume that the MB does the same thing, but I donât own one so that is just an assumption.
No one-way valve. In the Nissan, the top of the radiator is slightly above the coolant mark in the reservoir so when the engine is shut down, some coolant flows back into the reservoir and air goes from this port into the radiator. As soon as the engine is started, the level in the reservoir drops to normal and the radiator is filled back up to the top.
Thanks for your comments on your own pressurized overflow containers. Still curious what advantages this system has over the prior non-pressurized system? After all it must be more expensive to build a plastic container that holds pressure than one that doesnât, so there must be some advantage. The only thing I can think of is it might make the pressure regulating device (cap) a more simple design. Not ignoring what @keith speculates, helps keep air out of the cooling system. But hard to understand why it would do that better than the non-pressurized method?
For one thing, it eliminates the old style pressure cap between the radiator and the non-pressurized reservoir. The failure of that cap led to many an overheated engine.
??? âŚIf it only moved the cap from the radiator to the plastic tank, that doesnât seem like it would convey much in the way of an advantage. But if the cap on the plastic tank is less prone to failure than the one on the radiator, that would be a good advantage.
Tester
The newer style caps ARE less prone to failure. Theyâre a simple, solid cap, without the failure prone pressure release hardware.
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Good to know the pressure-tank system caps are more robust . I was also speculating that the pressurized coolant overflow tank configuration may take less space in the engine compartment.
There is less evaporative loss with a closed system.
The reservoir is in a cooler location for the pressure regulating cap, that is why they tend to last longer, the top of the radiator is 220 F.
Below is a 1977 Volkswagen with a pressurized reservoir.
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