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Old 08-04-2013, 09:35 AM
John in VA John in VA is offline
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Location: Leesburg, VA
Join Date: Feb 2006
Posts: 321
Mein Auto: '74 tii / E28s / '03 530i
Originally Posted by bluebee View Post
So, if the expansion cap is the one-way coolant overflow valve (with a two-way air check valve built in), then what is the purpose of the so-called expansion tank overflow tube that goes from the expansion tank neck to the top of the radiator?
I thought that as the coolant was heated, it "expanded" and moved from cooling system (radiator) to the expansion tank. After the car is stopped (cools), coolant is drawn back into the radiator.
E28 & E30 expansion tanks have hoses that vent excess coolant to the ground.
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