The coolant will effectively elevate the boiling point of the liquid, giving you better cooling properties. So, short answer is if it's only a little, water is fine..
In this way, is it OK to put water in coolant reservoir?
In general, using water as coolant is OK for a short time or as a "get you home" alternative, but it does not have the anti-freeze and corrosion inhibiting properties of a proper coolant mix, so should not be left in the engine for any length of time, especially if you live in a cold climate.
Furthermore, what happens if you add water to 50/50 coolant? Older formulations required the addition of water to dilute the coolant; the one you are referring to is pre-diluted. If there is currently a mixture of coolant and water in the radiator, it's fine to add the 50/50 mixture. Typically nothing. Especially since there is no exact amount of coolant to go in a system.
Hereof, what happens if you add water to antifreeze?
Your car's cooling system needs coolant to keep it from overheating. Although water can be added to the radiator for this purpose, it's preferable to add a mixture of coolant and water because plain water can boil before the proper coolant will boil, causing your engine to overheat [source: pontiac].
How do I add water to my coolant?
To add liquid to your radiator, follow these steps:
- Open the radiator cap.
- Look into the radiator fill hole to see how high the liquid level is inside.
- Add water and coolant, or pre-diluted coolant, as necessary.
- Replace the cap by screwing it on clockwise.
Related Question Answers
Can I use water instead of coolant in an emergency?
Yes, you could use water as a coolant in an emergency. However, doing so is not recommended since water won't work well beyond its freezing and boiling points. Remember also to regularly check the coolant level and cooling fan to avoid future problems with your cooling system.Can I top up coolant reservoir with water?
Your car's cooling system needs coolant to keep it from overheating. Although water can be added to the radiator for this purpose, it's preferable to add a mixture of coolant and water because plain water can boil before the proper coolant will boil, causing your engine to overheat [source: pontiac].How long can you run an engine without coolant?
If the coolant is not flowing, then it may have to absorb the heat from the motor. It is possible for you to run the engine for 15 seconds, but not longer than that if your car is running right.Why is the coolant reservoir empty?
If the coolant reservoir is completely empty, you can't just refill it. You need to check the level of coolant in the radiator as well. Wait until the radiator has cooled. Opening it hot can cause serious burns (very hot coolant can spray out).Can I top off my coolant with water?
It'll be fine to top off. Water should be mixed in coolant any ways. You don't put the stuff straight into the radiator or reservoir, you're supposed to cut it.Is it OK to mix coolant with water?
No! You should never mix coolant fluid with regular tap water. Tap water contains minerals that can form deposits inside the radiator and cooling system passages of your engine. This and the proper mixture of coolant and distilled water will help your car and its cooling system run without breaking for a long time.Do I put coolant in the radiator or reservoir?
If your engine is cold, the coolant level should be up to the cold fill line. If the coolant level is low, add the correct coolant to the reservoir (not the radiator itself). You can use diluted coolant by itself, or a 50/50 mixture of concentrated coolant and distilled water.How often should you top up coolant?
You need to check your engine coolant at least twice a year before summer and winter, ideally. Although, this advice may vary between car manufacturers. Coolant should be topped up whenever the level drops below the guide marks.What happens if you don't mix water with coolant?
Nothing, as long as you dilute it properly by adding enough distilled water directly as well. It won't cool any better or worse, but it will be more concentrated and this likely more corrosive to the internal parts and thus can increase the likelihood of leaks and issues down the line.Why is antifreeze mixed with water?
Antifreeze is mixed in equal parts with water to create a coolant solution that provides both freezing and boilover protection compared to straight water. Water is an efficient conductor of heat, which is good for cooling the engine and transferring heat to the radiator and heater core.Can you add coolant without flushing?
Yes. You cannot just keep adding coolant without ever flushing and changing it. Most cars need a flush and complete fluid change every 5 to 7 years.Does the car need to be running when adding antifreeze?
Yes, run the engine After you do any work involved with draining the coolant you will either have an exact process to remove air from the cooling system or you will simply run the engine. If you don't the gasses (air) will expand at a greater rate than liquid when the engine get's hot.How much water do I mix with antifreeze?
Mix an ethylene-glycol coolant with water in a 70:30 ratio (in other words, 70-percent coolant to 30-percent water). This is recommended if you live in an environment that experiences harsh winter weather. It is also the highest coolant-to-water ratio that most experts recommend for use in car engines.Is coolant and antifreeze the same?
Antifreeze is commonly used as one of the components of a coolant mixture – coolant is generally a 50-50 split between antifreeze and water. Antifreeze (specifically the ethylene glycol, which is its main ingredient) is used to lower the freezing point of the liquid that circulates around the engine of a vehicle.What happens if you put more coolant than water?
Water has a much higher specific heat than coolant - meaning that water will transfer more heat from the engine than coolant. A mix of coolant and water will lower the freezing temperatures and slighly raise the boiling temperature.Can I put water instead of coolant in my BMW?
I wouldn't risk driving cross country with water as coolant. The engineers spec for the cooling system is 50/50 BMW coolant, distilled water only. The coolant has corrosion and rust inhibitors and water pump lubricants. It's easier to just follow the instructions the engineers laid out for the engine.Is it OK to fill coolant with water?
In general, using water as coolant is OK for a short time or as a "get you home" alternative, but it does not have the anti-freeze and corrosion inhibiting properties of a proper coolant mix, so should not be left in the engine for any length of time, especially if you live in a cold climate.Is putting water in coolant bad?
In general, using water as coolant is OK for a short time or as a "get you home" alternative, but it does not have the anti-freeze and corrosion inhibiting properties of a proper coolant mix, so should not be left in the engine for any length of time, especially if you live in a cold climate.Can you add water to the coolant tank?
Your car's cooling system needs coolant to keep it from overheating. Although water can be added to the radiator for this purpose, it's preferable to add a mixture of coolant and water because plain water can boil before the proper coolant will boil, causing your engine to overheat [source: pontiac]. 
