Coolant is a crucial fluid for a vehicle that serves both to prevent overheating as well as freezing. It is made of water and antifreeze.
Given that it is a liquid, it is reasonable to ask: Does coolant evaporate? The answer is yes, coolant does evaporate, but under normal conditions, this should be a very slow evaporation that is not noticeable for years. Losing large amounts of coolant in a short period of time point to a problem.
How Long Does It Take For Coolant To Evaporate Normally?
As noted above, coolant should evaporate very slowly when nothing is going wrong. You might notice the overall coolant level drops around 1 inch in the reservoir over the course of a year.
This will of course vary by your specific vehicle and the operating conditions you drive it under, but this is a good rule of thumb for an intact cooling system.
How Long Does It Take Coolant To Evaporate When Something Is Wrong?
There is not a straightforward answer to this question because it depends both on what is wrong with the vehicle as well as both coolant evaporating or simply leaking.
So what are some possible causes for coolant leaks and excess evaporation?
Faulty or Loose Radiator Cap
The radiator is sealed off by its cap. This is not a normal twist on/off cap; it is a pressurized cap and if it is not tightened properly, you will experience leaks. If the cap is worn out, it also might not seal effectively, leading to the same problem.
Normally the cooling system is sealed, so having a radiator cap that is not pressurized as it should be will lead to leaks and premature evaporation as the fluid is exposed to the air.
Bad Radiator Hoses
Your engine bay will have multiple hoses, some of which are specifically for your cooling system. Normally, these hoses are composed of rubber or silicone, and can wear out over time (especially rubber hoses). If they are cracked, you will likely see an obvious leak.
Even if there is no obvious leak but the hoses are worn down, it is best to replace them as soon as possible to avoid future coolant loss.
Damaged System Components
The cooling system has multiple parts, such as the radiator, a water pump, thermostat, etc. If any of these parts are damaged, such as in an accident, coolant might leak and/or evaporate as it becomes exposed to the atmosphere.
Sometimes these components might become worn over time, too, as the vehicle’s age and milage increases, even if no accident occurred. Regular inspection is essential to ensure worn parts are noted and replaced before you experience coolant loss.
Adding Too Much Coolant
A vehicle’s manual will specify how much coolant should be added to the tank. If you happen to put in too much, it is likely the radiator cap will be unable to contain it and pop open, leading to fluid flowing out.
This is, of course, a user error and one that can be avoided by double checking the exact amount of coolant ought to be in the system. Usually the manufacturer’s manual for your particular make and model will specify where the coolant level should be both when the engine is cold and when it is hot. Be sure to pay attention to this; you do not want to fill the coolant to the max level, for instance, if you are only supposed to fill it to the mid-point between max and min levels.
Using The Wrong Coolant
Along with pouring in too much coolant, using the wrong type of coolant can lead to leaks and evaporation. Every vehicle will have specifications as to which type of coolant should be used.
If you use the wrong type of coolant, you can damage parts like the water pump, which can result in a leak. Not only will the vehicle’s cooling not be functioning optimally, but you risk ruining components of the vehicle itself as well as losing the incorrect coolant to begin with.
Having Dirty or Contaminated Coolant
Sometimes the coolant ought to be flushed and replaced with new fluids. It can be visually inspected at regular intervals for the presence of dirt and/or discoloration. If the coolant becomes contaminated, this can damage the components the coolant flows through, and this damage can lead to holes and subsequent leakages.
Although this is not totally due to driver error, like overfilling your coolant tank or just using the wrong kind of coolant, failing to regular inspect and remove contamination in a timely manner can lead to damage and leaks. If you are unsure what to look for or are someone who just wants a professional to service your vehicle, be sure to remind your mechanic or technician to check on your fluids and if contaminated, replace them.
Blown Head Gasket
The head gasket is a part of your engine that seals off the combustion chamber, essentially. If this is defective or damaged, it is highly likely coolant, along with engine oil, will leak.
This is a dramatic problem and you are likely to notice white smoke billowing from your exhaust pipes before you even notice the coolant loss, and your engine is also likely to overheat at the same time and suffer damage both with regard to coolant and engine oil loss.
In Sum
Coolant should not evaporate rapidly under normal operating conditions. It should be a fairly slow process that is not noticeable from day to day. If you happen to notice large drops in your coolant tank under the hood, or leaks that appear to be coolant, this signals a deeper problem.
It can be due to something as simple as not tightening the radiator cap properly, using the wrong coolant, or using too much coolant, as well as more complex issues like damage to one or more components of the cooling system or even the engine’s head gasket.
Coolant evaporation should only occur at a minimal rate, anything other than this warrants immediate attention to prevent possible overheating and therefore engine damage.