E46Fanatics - View Single Post - [Cooling System Upgrade] 1-BAR Radiator Cap
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Old 10-03-2012, 09:41 PM   #13
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Join Date: Feb 2006
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My Ride: ESS TS2+ ZHP
Originally Posted by Solidjake View Post
So basically when the system is fully hot up to temp, when we loosen our caps that is why a lot of steam/hot air comes out. Wouldn't using this cap to lower the pressure force the water pump to work harder to move coolant around as it's not pressurized as it should be?
No, the coolant system pressure has no bearing on how hard the water pump has to work when the system is sealed. The reason coolant spews out when you remove the radiator cap from a hot engine is because there is now a pressure differential between the pressurized fluid and the surrounding air pressure.

Cars use a pressurized system to raise the boiling point of the coolant. This in turn allows the car to run hotter (at a temperature regulated by the thermostat) for improved emissions, etc. Depending on how much margin is designed into the stock cap, one very likely outcome of this experiment is a coolant leak from the cap due to the thermostat allowing coolant temps to create more system pressure than the 1-bar cap will allow.
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