Iced tea in coolant reservoir: A cause for concern?

Our tech guru has the answer
Feb 6, 2012

Hi, Ferman!

I added a liter of iced tea in the coolant reservoir of my trusty 1993 Mitsubishi Lancer GLi by mistake and drove for an hour. I mistook it for the coolant because I use the empty bottles for tap water reserve for filling up the radiator.

Would this have any short-term or long-term effect on my car?

Please advise. Thank you.


Hi, lancerlimbo,

There shouldn't be much long-term or short-term effect on your vehicle's cooling system as long as it's in fairly good working order.

When changing or topping up your cooling system's coolant (used here as a general term for the liquid you put in your vehicle's cooling system) it's best to use distilled water mixed with automotive coolant (typically an ethylene glycol based compound with corrosion inhibitors) in a 50/50 mixture. This mixture lowers the freezing point over water alone (while this isn't as critical for us here in tropical countries) and increases boiling point of the mixture to about 107 degrees Celsius (this is what we want) when not held under pressure (more on this later).

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While mixing water with coolant does lower the heat transfer capacity to less than that of water alone (thereby requiring an increase in fluid flow rate to achieve the same cooling effect) the increase in boiling point is desirable as when liquid boils to become vapor heat transfer capability is reduced immensely.

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The pressure caps in our cooling system also aid in increasing the boiling point of our coolant. I don't recall the exact increase in temperature per PSI of increase of the cooling system's pressure but if memory serves most modern vehicles with a 50/50 coolant/water mix with a 0.9bar (~13PSI) pressure cap will have their coolant mixture boil over at about 117- or 118-degree Celsius.

You'll notice that there is a trend to use a higher rated pressure cap on later vehicles as well as race cars. This is to further increase the boiling point as better efficiency over the engines in the past are being achieved with nowadays.

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With more engines being made out of aluminium, the anti corrosive additives of the coolant are required to prevent water from oxidizing the aluminium and damaging the components. Cast iron engine blocks also benefit from the anti-corrosives.

Best regards,

Ferman Lao
Tech editor

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