[juanespinoza11]

Hey guys, so every time I check my coolant in the mornings I notice it's not even visible on the Minimum line. I added coolant and only needed like 3 oz to get to minimum. I do check when the car is warm and it is on the max. Is this normal when the car is cold? I did change my reservoir about 2 months ago. Let me know what you guys see in the mornings in your tank!

[SnapCoupe]

Originally Posted by juanespinoza11

Hey guys, so every time I check my coolant in the mornings I notice it's not even visible on the Minimum line. I added coolant and only needed like 3 oz to get to minimum. I do check when the car is warm and it is on the max. Is this normal when the car is cold? I did change my reservoir about 2 months ago. Let me know what you guys see in the mornings in your tank!

Totally normal. Theres a reason why its called an "expansion tank". When the car warms up the coolant expands and the level will appear higher than what it was cold. The proper way to top-off your coolant is filling it just below the max level when the car is stone cold.

[Pladi]

Originally Posted by juanespinoza11

Hey guys, so every time I check my coolant in the mornings I notice it's not even visible on the Minimum line. I added coolant and only needed like 3 oz to get to minimum. I do check when the car is warm and it is on the max. Is this normal when the car is cold? I did change my reservoir about 2 months ago. Let me know what you guys see in the mornings in your tank!

My tank is not a morning tank it likes to sleep in.. sorry

[juanespinoza11]

Originally Posted by SnapCoupe

Totally normal. Theres a reason why its called an "expansion tank". When the car warms up the coolant expands and the level will appear higher than what it was cold. The proper way to top-off your coolant is filling it just below the max level when the car is stone cold.

Thanks!

[Efthreeoh]

Originally Posted by SnapCoupe

Totally normal. Theres a reason why its called an "expansion tank". When the car warms up the coolant expands and the level will appear higher than what it was cold. The proper way to top-off your coolant is filling it just below the max level when the car is stone cold.

I have to take issue with this nomenclature, but not with you, with BMW. It's really not an expansion tank because it is pressurized and the cooling system pressure relief (i.e. radiator cap) is on the tank. The tank is really the coolant reservoir, because the majority of the coolant stored in the cooling system (outside of the engine block) is in the tank and not in the radiator. Expansion tanks are non-pressurized and hold excess coolant in reserve depending upon the temperature of the coolant. It is not dangerous to open the cap on an expansion tank when the engine is hot, but it is VERY dangerous to open the cap of the E9X coolant reservoir when the engine is hot.

Just a pet peeve of mine.

But to the OP's question, obviously only open the reservoir cap when the engine is cool and the cooling system has no pressure in it. But what you are witnessing is the normal expansion of the coolant under different states of temperature. And stop being so OCD about your car. You have Bmwitice.

[blown07]

It is exactly an expansion tank.

[juanespinoza11]

Originally Posted by Efthreeoh

I have to take issue with this nomenclature, but not with you, with BMW. It's really not an expansion tank because it is pressurized and the cooling system pressure relief (i.e. radiator cap) is on the tank. The tank is really the coolant reservoir, because the majority of the coolant stored in the cooling system (outside of the engine block) is in the tank and not in the radiator. Expansion tanks are non-pressurized and hold excess coolant in reserve depending upon the temperature of the coolant. It is not dangerous to open the cap on an expansion tank when the engine is hot, but it is VERY dangerous to open the cap of the E9X coolant reservoir when the engine is hot.

Just a pet peeve of mine.

But to the OP's question, obviously only open the reservoir cap when the engine is cool and the cooling system has no pressure in it. But what you are witnessing is the normal expansion of the coolant under different states of temperature. And stop being so OCD about your car. You have Bmwitice.

Lolol thanks buddy

[vb7200]

Mine has none, since it has a leak...