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'03 e46 M3
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20 Posts
Discussion Starter · #1 ·
All preventive maintenance recommendations lists the coolant expansion tank as a necessary item to replace after a certain mileage, say 100K. My question is "why". If the car never overheated, has the expansion tank really been used? I understand changing the various hoses, but why specifically the expansion tank? Any advice will be appreciated.

Thanks
Paul
 

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It's plastic. Coolant gets hot and cold. With the constant temperature changes it causes the plastic to fatigue and crack over time.

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'03 e46 M3
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20 Posts
Discussion Starter · #3 ·
Ah, I thought that the expansion tank is filled with the coolant only on rare occasions
Thanks
 

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E30M3 Race F10 535 R1150Rt M Coupe
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Not an overflow tank as on Japanese cars. Thiers are after the cap
Yours is in the coolant loop and where the cap lives.
 

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