E46Fanatics - View Single Post - E46 COOLING SYSTEM GUIDE - overheating/coolant/etc
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Old 05-14-2012, 08:10 PM   #203
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They look to be made by the exact same manufacturer. Would a lower psi rating benefit anything? It'd keep the system under less pressure, meaning that it will have a lower boiling point. Would it preserve the expansion tank longer? The only worry I'd have would be overheating.

1999-2004 Land Rover: 15 PSI

You may be onto something here if it prolongs the cooling system life; however, BMW chose 30 PSI for a reason. We all know how hot our engines run, it may be that the Range Rover engines run cooler.

By using a 15 PSI cap, you are effectively reducing the boiling point by about 37 degrees F. Note that this does not take into account the increased boiling point properties that the anti-freeze adds, too, which is not much (~15 degrees F).

What is the normal operating temperature of our engines?
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