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Old 10-05-2012, 10:06 AM   #80
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Join Date: Aug 2012
Location: Gulfport, MS
Posts: 510
My Ride: 2002 325i
Originally Posted by SeanC View Post
^Yep, we both got surprisingly low value for pressure at operating temperature. Makes the use of a 2-bar cap even more of a mystery in the e46. Even more so given that the e90's use only a 1-bar cap. Wonder what exactly is different between two systems.
So, all this theory is interesting, but I wonder if something is being missed in practice?

I have three other cars that have 15 PSI relief caps. Once heated up, I can squeeze on a radiator hose and tell that the system is pressurized, but not how much. On the BMW, when I squeeze on the hose (once heated up), there is noticeably more resistance to squeezing than the other cars. To me, this implies that it is indeed pressurized to a higher pressure than the other cars I have.

We can speculate about this, but I suggest that it is easy to find out for certain. Just tap a small pressure gauge in and find out what pressure it goes to. It seems like the bleed screw on the upper radiator hose would be a good place to do it. It would be a sacrifice of a $25 hose, so not too bad.
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