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Discussion Starter #1
My CRV has a tank attached to the radiator. According to the handbook it is a coolant reserve tank. I have owned this car for a year and paid no attention to this tank as I thought it was just to hold the overflow from the radiator. The level was always around half. Today I noticed the level has dropped and on closer inspection I see there is a minute and Max mark on the bottle. Mine is now sitting close to min. Does anyone know what the purpose of this tank is and should I top it up?
 

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2010 EX-L (AWD, non-Nav)
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It's integral to the performance of the cooling system. Yes, you do need to check the level every now and then and add coolant if necessary. Halfway between min and max is fine.

It exists on all cars because when coolant heats up, it expands. But, the cooling system can't expand with it, so they designed the radiator cap to allow excess coolant to be diverted to the overflow tank. When things cool down, the process reverses itself and some coolant from that tank gets sucked back in to the radiator.

If this tank ever gets empty, you could end up with an air bubble in the system, which is bad.
 

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Keep an eye on the level or top it up yourself or during next oil change ask them to do it for you
 

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Discussion Starter #4
Thanks a lot guys I have always been checking the level at the radiator cap. It looks like it may have lost about 200ml over a year 20000km of driving. Should I be concerned about possible leaks.?
 

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2010 EX-L (AWD, non-Nav)
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Check the level at the overflow tank, not the radiator cap. We yankees don't know how much 200ml is so I can't say if that's a lot or not.
 

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ALWAYS check BOTH the radiator coolant level and the level in the bottle when the motor is COLD. Coolant level in the radiator, COLD motor, should be up in the neck of the radiator.....if not, you could have a bad radiator pressure cap. The radiator pressure cap has 3 sealing surfaces and 2 coolant passages. All 5 components must be working perfectly. Radiator caps are inexpensive to replace. Coolant level in the bottle, COLD motor, should be at, or slightly above, the MIN/COLD mark on the side of the bottle.
 

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Per your manual, when you add coolant to the reservoir bottle fill it to the full mark. 200ml per 20000km ( 7 oz. per 12k miles) is a little high but not too bad. But get a flashlght and look for a leak just to be sure you don't have one. Some coolant will leak pass the water pump seal and drain out the weep hole of the water pump. This is normal especially in high mileage vehicles. When you start seeing some coolant on the garage floor or your coolant loss increases, it's time to get it checked.
 

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Discussion Starter #8
Thanks a lot for the informative replies guys especially to Traylaw for the metric conversions. (y)
 

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'07 CR-V EX-L AWD
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Moved to Gen 4 Section.
 

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It's integral to the performance of the cooling system. Yes, you do need to check the level every now and then and add coolant if necessary. Halfway between min and max is fine.

It exists on all cars because when coolant heats up, it expands. But, the cooling system can't expand with it, so they designed the radiator cap to allow excess coolant to be diverted to the overflow tank. When things cool down, the process reverses itself and some coolant from that tank gets sucked back in to the radiator.

If this tank ever gets empty, you could end up with an air bubble in the system, which is bad.
Your owner's manual tells you exactly when and how to check the level
 

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ALWAYS check BOTH the radiator coolant level and the level in the bottle when the motor is COLD. Coolant level in the radiator, COLD motor, should be up in the neck of the radiator.....if not, you could have a bad radiator pressure cap. The radiator pressure cap has 3 sealing surfaces and 2 coolant passages. All 5 components must be working perfectly. Radiator caps are inexpensive to replace. Coolant level in the bottle, COLD motor, should be at, or slightly above, the MIN/COLD mark on the side of the bottle.
Wrong - you don't take the cap off a closed system. You check at the reserve tank. With this system the radiator is always 100% full if there is fluid in the tank. Every time you open the cap you lose fluid.
 

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Wrong - a “closed” system has pressurized bottle, no cap on the radiator.
 
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