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Old 03-08-2013, 09:15 AM
Dragan Dragan is offline
Officially Welcomed to the 'Fest
Location: Waterloo, Ontario
Join Date: Jan 2013
Posts: 194
Mein Auto: 2002 BMW 530i Sport 5 Spd
Originally Posted by 540iman View Post
Finally, a ray of light. BMW owners seem (I do too at times) to jump at any perceived superior device than what BMW gave us. The pressure that the cap will hold will make absolutely no difference in how your car performs, how you will survive say a massive radiator leak while stuck in traffic, or in normal driving. You could put a 3 bar cap on with no difference in how the car performs, the temperature the car attains nor will it possibly save you in a failure. Where it may make a difference is if you accidentally over-fill the system to the point where the coolant has no place to expand to. The cap should (if the coolant reaches an excessive pressure) release the "extra" coolant. The tests performed here on this post demonstrate that this will exceed 1.2 bar or 1.4 bar and the longer you can keep your coolant in the closed system the better. Remember the cap is rated in pressure and no relation to temperature. A cooling system full of just water will increase pressure at a lower temperature than one filled with coolant. Cap Has no effect on temperature, only on pressure.
I'd like to just point out that temperature and pressure are directly proportional to one another. One goes up, so does the other assuming the volume of the system remains unchanged. If it the temperature/pressure of the cooling system gets high enough (2 bar in this case), the spring-loaded cap will vent the excess pressure to atmosphere.
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