What do I do if the coolant reservoir is completely empty?

What do I do if the coolant reservoir is completely empty?
Experienced mechanics share their insights in answering this question :
The coolant reservoir on your Accord is connected to the radiator, and allows coolant to flow back and forth between the two as it heats and cools. 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. Here’s how to do that:

Wait until the radiator has cooled. Opening it hot can cause serious burns (very hot coolant can spray out).
Turn the radiator cap counterclockwise, but don’t press down on it. This will release any built up pressure.
Push down and turn counterclockwise on the cap.
Remove the cap and check the level of coolant in the radiator. It should be no lower than the bottom of the radiator neck.
If the coolant is low, top it off. Add fresh coolant slowly and clean up spills immediately.
Replace the radiator cap.
Top off the coolant reservoir.

Tip

If both the radiator and reservoir are low on coolant, it could signal a leak somewhere in the system.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

With your coolant reservoir empty, your coolant system can`t draw in extra coolant when it needs it. This can lead to overheating. You can top up the reservoir, but you also need to identify where that coolant went.
Only Use Water In The Radiator In An Emergency

If it`s really low or actually empty, you need to add fluid to your vehicle. While it`s ideal to add a 50/50 mix of coolant and water (or a pre-mixed coolant), if you absolutely have to keep driving, you can add water to the radiator to get you to your destination.

Technically speaking yes you can use plain water in your cooling system but it isn`t recommended as a long term solution and certainly not in extreme weather conditions.
If you`ve only popped out on a short drive in town, the radiator won`t be all that hot at all, and should cool down within 20 to 30 minutes. However, if you`ve been gunning it on the motorway, you can expect to wait around an hour for the radiator to cool down enough for it to be safe to handle.
Many people know that when it`s freezing outside, their radiator needs antifreeze or engine coolant. And now you know that antifreeze and coolant are basically the same thing and can be generically referred to as radiator fluid.
A functioning cooling system is crucial to the ongoing performance and health of your car`s engine, so it`s important to make sure the coolant/antifreeze level never drops below the minimum fill line marked on the reservoir.
The coolant level should be between the F(full) and L(low) marks on the side of the coolant reservoir.”
A functioning cooling system is crucial to the ongoing performance and health of your car`s engine, so it`s important to make sure the coolant/antifreeze level never drops below the minimum fill line marked on the reservoir.
One of the major causes of the engine overheating is a leak in a coolant system. If you find fluid around the hose or radiator cap, some pooling under the car, especially when your coolant reservoir tank is empty, then there is a leak. It is important to remember that all cooling systems depend on pressure to function.
One of the major causes of the engine overheating is a leak in a coolant system. If you find fluid around the hose or radiator cap, some pooling under the car, especially when your coolant reservoir tank is empty, then there is a leak. It is important to remember that all cooling systems depend on pressure to function.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

No coolant in the reservoir. Seen low coolant message. I added 2 quarts of 50/50 coolant. Still getting the message. How much coolant doe it need?
ANSWER : Hi there. For the coolant light to go out, you would need to have the coolant between the low line and the full line for the light to go out. If the coolant is low and keeps on being low, then look for any signs of coolant leaks. You may have to use a coolant pressure tester to pressurize the reservoir to allow the leak to be found.

If you need further assistance with the coolant being low and the warning light being on, then seek out a professional, such as one from Your Mechanic, to help you.

My 05 equinox is overheating. Refilled coolant reservoir this morning for the reservoir was empty, but I cant find any coolant. Now heater is blowing cold.
ANSWER : Hi there. If the engine is overheating to almost at the red line but not there, then the issue would be the thermostat and leaking out the blow by hose. If the needle is going into the red line, then the coolant could be leaking out of a freeze plug and burning off on the exhaust or leaking into the engine causing the oil to mix. Check the engine oil and see if it is milky. If the oil is milky, then there is coolant getting in the oil through the intake gaskets or the head gaskets. If you need further assistance with your engine overheating, then seek out a professional, such as one from Your Mechanic, to help you.

My coolant reservoir is empty and coolant is splattered over my engine
ANSWER : Driving a car with "zero" coolant will destroy the engine within minutes. Even after a coolant leak, though, you have some coolant in the engine and water can sometimes be added to enable one to drive a "short" distance as long as you observe the temperature gauge on the instrument panel and do NOT operate the car, even momentarily, in the RED (overheated) danger zone. But, the problem is because we do not know the nature and extent of the coolant leak that you have, once you add water (or anti-freeze) it is hard to predict if it will leak out quickly, thus quickly leading to an overheating situation once you depart, and possibly leaving you stuck between home and a service facility. When the car is stone cold (if you open cap when engine is hot you will be severely burned), you could try removing the radiator cap, adding water, re-installing the cap tightly and see if the car will idle for 10 minutes without overheating and without coolant leaking out. If the car seems "stable", you could "try" to make it to a shop.

As far as what’s wrong, you have a leak, the origin of which is usually obvious once a mechanic makes just a visual inspection. There are so many places a cooling system can leak: radiator cap, water pump, radiator, hoses, and so forth. All of those are easy to deal with though and so you needn’t worry. It will be least risky (in terms of potentially overheating the engine), and also much less expensive, if you have a certified mobile professional come right to your door and resolve this for you. If you desire, do follow-up with YourMechanic and request a cooling system leak diagnostic during which the Mechanic will let you know exactly what the story is. If I can be of further service, or you have additional questions, please do not hesitate to contact me.

My coolant reservoir is empty and coolant is splattered over my engine
ANSWER : Driving a car with "zero" coolant will destroy the engine within minutes. Even after a coolant leak, though, you have some coolant in the engine and water can sometimes be added to enable one to drive a "short" distance as long as you observe the temperature gauge on the instrument panel and do NOT operate the car, even momentarily, in the RED (overheated) danger zone. But, the problem is because we do not know the nature and extent of the coolant leak that you have, once you add water (or anti-freeze) it is hard to predict if it will leak out quickly, thus quickly leading to an overheating situation once you depart, and possibly leaving you stuck between home and a service facility. When the car is stone cold (if you open cap when engine is hot you will be severely burned), you could try removing the radiator cap, adding water, re-installing the cap tightly and see if the car will idle for 10 minutes without overheating and without coolant leaking out. If the car seems "stable", you could "try" to make it to a shop.

As far as what’s wrong, you have a leak, the origin of which is usually obvious once a mechanic makes just a visual inspection. There are so many places a cooling system can leak: radiator cap, water pump, radiator, hoses, and so forth. All of those are easy to deal with though and so you needn’t worry. It will be least risky (in terms of potentially overheating the engine), and also much less expensive, if you have a certified mobile professional come right to your door and resolve this for you. If you desire, do follow-up with YourMechanic and request a cooling system leak diagnostic during which the Mechanic will let you know exactly what the story is. If I can be of further service, or you have additional questions, please do not hesitate to contact me.

Over heating coolant not siphoning back into coolant over flow tank
ANSWER : Hey there:

It’s common for many mechanics to make the mistake of mis-diagnosing the cause of an overheating situation; especially when they assume it’s a thermostat issue. The problem could be caused by a blockage in the coolant tubes running from the radiator to the overflow tank and back to the radiator. However, it also may be due to air trapped in the coolant lines. I think a good idea would be to contact a different ASE certified mechanic, such as one from YourMechanic, and have them complete a coolant flush, which should remove any blockages in the coolant tubes and may solve your problem.

What do I do if the coolant reservoir is completely empty?
ANSWER : The coolant reservoir on your Accord is connected to the radiator, and allows coolant to flow back and forth between the two as it heats and cools. 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. Here’s how to do that:

Wait until the radiator has cooled. Opening it hot can cause serious burns (very hot coolant can spray out).
Turn the radiator cap counterclockwise, but don’t press down on it. This will release any built up pressure.
Push down and turn counterclockwise on the cap.
Remove the cap and check the level of coolant in the radiator. It should be no lower than the bottom of the radiator neck.
If the coolant is low, top it off. Add fresh coolant slowly and clean up spills immediately.
Replace the radiator cap.
Top off the coolant reservoir.

Tip

If both the radiator and reservoir are low on coolant, it could signal a leak somewhere in the system.

Topped off coolant with Prestone Universal Coolant. Manual says to use MOPAR HOAT. Do I need to get a flush before a long trip?
ANSWER : Not knowing which exact type of coolant was used to refill the system after the block heater install, I would consider flushing the cooling system and refilling with the correct coolant. Years ago, we just had "green coolant that went into every car. In recent years, different manufacturers call for different coolants. There are a number of different metals in contact with the coolant nowadays. The engine block can be cast iron, the cylinder heads can be aluminum. The head gasket may have steel rings surrounding each cylinder bore. The coolant has to be able to interact with all the different metals and not cause additional corrosion. Mixing different coolants can cause some issues. Sometimes the mixture can cause gelling and clog smaller passages in the radiator and heater core. They can also interact poorly with the different metals when mixed. I’ve replaced a few heater cores because they were so badly clogged from mixed coolant. Considering these things and the climate you are taking the vehicle to, a cooling system flush is definitely a good idea.

Coolant flush before winter?
ANSWER : I would recommend flushing the coolant and adding new since you just bought the truck and may not know the history of the maintenance prior. The reservoir is connected to the radiator and simply allows the coolant to flow back and forth between the two as it heats and cools.