My car is spitting coolant from the overflow tank

2004 Chevy Tracker started spitting coolant from the overflow tank. No overheating problems or leaks beforehand until now.

Without any warning, most of the coolant had blown out of the overflow tank. After allowing it to cool for a couple of hours, I refilled the radiator and overflow tank to recommended levels. Drove it another ~6 miles and it started overheating again. Opened the hood and found the overflow tank FULL and spitting coolant again.

The system appears leak free but obviously something ain't right given the symptoms. The coolant system was replaced four years ago after

Experienced mechanics share their insights in answering this question :
Hi and thanks for contacting YourMechanic. Check the coolant strength to see what the protection is. A good protection will read 164 degrees Fahrenheit. Check the radiator cap to see if the seal is torn or if the release valve inside the cap has failed or is sticking open. A radiator cap can cause the system to boil and spit out all of the coolant.

If you have good coolant and the radiator cap is new, then the thermostat could be sticking causing your coolant to heat up too much which in turn causes the system to boil. To check if the thermostat is working, start up the vehicle when it is cold and watch the coolant temperature gauge. When the thermostat opens, the gauge will drop a little.

If the gauge does not show this, then, when the upper radiator hose gets hot, right after the thermostat opens, the coolant flows through the hose and you would be able to feel this. Plus, the hose will begin to get cooler as the coolant travels through the hose. If the thermostat was replaced and you still have a boiling issue, then the head gasket has burned on the engine.

If you need assistance, then seek out a professional mechanic, such as one from YourMechanic, to help determine why the car is overheating and why the coolant is boiling out.

How to Identify and Fix Common car Problems ?

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There are a few reasons your car might be spitting coolant from the overflow tank. The most common reason is that the coolant level in the radiator is too high. When the coolant level gets too high, it can cause pressure to build up in the system, which can force coolant out through the overflow hose.
A radiator cap can cause the system to boil and spit out all of the coolant. If you have good coolant and the radiator cap is new, then the thermostat could be sticking causing your coolant to heat up too much which in turn causes the system to boil.
The most common cause of bubbles in the coolant tank is a worn or blown head gasket. When the head gasket fails, combustion gases from any cylinder leak into the water jacket, forcing air into the cooling system through the cylinder head.
Antifreeze leaks can be caused by a variety of things but the two most common factors are age and dirty coolant. Dirt or oil in your coolant can accelerate wear in your system, leading to leaks in your water pumps, at gaskets, or at o-rings. Flushing your cooling system is the best way to stop this type of leak.
Most of the time, excess coolant is expelled from an overflow hose. You`ll likely see a puddle of coolant beneath your car if this has happened. In worst case scenarios, overfilling your antifreeze tank can lead to electrical damage if overflow comes into contact with engine wiring.
To release pressure, the radiator cap allows some coolant to escape out, stored in the reservoir. This excess coolant stays here until the system cools down enough to create negative pressure and draw the excess coolant from the reservoir back into circulation.
The coolant level should be between the F(full) and L(low) marks on the side of the coolant reservoir.”
Faulty thermostat valve: A fault in the thermostat housing may prevent the thermostat valve from opening, resulting in the engine overheating. If your engine continues to overheat, it`ll cause your cars coolant reservoir to overflow.
Expansion and recovery tanks are typically mounted at the highest point in the cooling system to let out air and allow for thermal expansion of the fluids when it heats up. In performance applications like racing, the overflow tank is just an overflow of your expansion that acts as a catch can.
Whining or Groaning Noise

A whining or groaning noise usually means that either a drive belt is loose, or the water pump pulley is bad. It may surprise your customer that a pulley could fail. It does occasionally happen. Pulleys may fail due to rust, which can cause cracking between their bolt holes.

Common problems include overheating, leakage, low water pressure, noisy operation, and cavitation. These problems can be prevented or fixed by regular maintenance, inspection, and replacement of worn-out parts.
Start your car`s engine and allow it to idle. Look through the radiator filler neck to see if the coolant flows. At this time, it should not be flowing as your car has not reached the operating temperature to cause the thermostat to open. If you find the coolant is flowing, it means the thermostat valve is open.
For this, you need a container (large enough to accommodate the reservoir), fill it with bleach, dishwashing liquid, and water. Now place the reservoir into the container and allow it to sit for a few hours, and you can also let it stay overnight.
An average engine holds about 3 quarts (2 liters) of coolant, but this amount may vary depending on the vehicle`s make, model, and type. For example, some Toyota models use only 1.5 quarts (1.5 liters), while others require 3 quarts (3 liters).
Engine Coolant Volume

Most cooling systems will hold around 5 litres. DIY Car Service Parts sell engine coolant in 1-20 litre containers, so you can purchase the exact amount that you need. Follow these simple steps to replace your engine coolant.

Faulty coil in the hot water cylinder

Over time, this coil can become perforated, meaning there`s hole in the coil which allows water for the central heating into the domestic hot water being stored in the cylinder. This rise in water levels can then lead to the feed and expansion tank overflowing.

In normal use the expansion tank on a hot water heating system is never full – so the bottom of the tank gets hot but the upper tank, wher there should be air, stays cooler. If the tank becomes waterlogged – loses its air charge – then we`ll see dripping or discharge at the boiler temperature/pressure relief valve.
Allowing your water tank to overflow accomplishes two primary goals: Creates an exit path for excess incoming water. Helps to remove floating particles from the surface of the water.
Faulty Thermostat

Once the engine reaches operating temperature, the valve will open and coolant will begin to flow through the engine. A faulty thermostat might remain closed even when the engine is hot, which can quickly lead to overheating.

The short answer is yes, but it is not recommended. Ignoring a blown head gasket will likely lead to more damage to your engine as well as your wallet. Gaskets are some of the most important and necessary parts of any engine which function to seal off compartments.
You can also try performing a compression test of your engine to find a head gasket leak. If your head gasket is blown, it will allow the compressed air in 1 or more cylinders to bleed off into the cooling system lowering the compression in that cylinder.
If your coolant reservoir is boiling but your engine doesn`t overheat, then your coolant may not actually be too hot. Those bubbles you noticed are more likely air bubbles that found their way into the coolant reservoir—not from the piping hot coolant. In most cases, the issue is actually a leak in the radiator cap.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My car is spitting coolant from the overflow tank
ANSWER : Hi and thanks for contacting YourMechanic. Check the coolant strength to see what the protection is. A good protection will read 164 degrees Fahrenheit. Check the radiator cap to see if the seal is torn or if the release valve inside the cap has failed or is sticking open. A radiator cap can cause the system to boil and spit out all of the coolant.

If you have good coolant and the radiator cap is new, then the thermostat could be sticking causing your coolant to heat up too much which in turn causes the system to boil. To check if the thermostat is working, start up the vehicle when it is cold and watch the coolant temperature gauge. When the thermostat opens, the gauge will drop a little.

If the gauge does not show this, then, when the upper radiator hose gets hot, right after the thermostat opens, the coolant flows through the hose and you would be able to feel this. Plus, the hose will begin to get cooler as the coolant travels through the hose. If the thermostat was replaced and you still have a boiling issue, then the head gasket has burned on the engine.

If you need assistance, then seek out a professional mechanic, such as one from YourMechanic, to help determine why the car is overheating and why the coolant is boiling out.

Read Full Q/A … : My car is spitting coolant from the overflow tank

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.

Read Full Q/A … : My car is spitting coolant from the overflow tank

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.

Read Full Q/A … : My car is spitting coolant from the overflow tank

My car is leaking coolant and telling me to stop the car and check coolant.
ANSWER : Going by your description and the age of the car, I’m going to guess you have a problem with your water pump. The water pump has a rotating seal that often doesn’t leak unless the engine is running. If your water pump is leaking you might be able to see a drip from the bottom of the engine front cover. Before jumping to any conclusions though, you should have a professional pressure test the system to be sure. If you contact Your Mechanic. they can send a technician to your home or office to check out your leak and tell you what it will take to solve it.

Read Full Q/A … : My car is spitting coolant from the overflow tank

A piece of cardboard/paper from the coolant jug was accidentally dropped into the coolant tank.
ANSWER : Unfortunately, this tiny piece of cardboard will not dissolve in coolant as it is designed to withstand the chemical makeup of the coolant. This can become lodged in areas inside the radiator that will prevent the proper flow of coolant through the passages. I would suggest having an expert from YourMechanic come to your home to properly remove the debris from the radiator at your own convenience.

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Car won’t start.leaking coolant antifreeze out of drain hose.changed coolant tank cause had a crack in it.now car won’t start
ANSWER : Hi there. There are several reasons why you might be experiencing overheating issues with your car. However, without knowing the vehicle details, it’s hard to give you a good diagnosis. It could be the water pump, bad thermostat, an air bubble in the coolant lines, or a blown head gasket in the worst case.

The best thing I can recommend for you is to contact a local ASE certified mechanic to inspect the vehicle’s starting issue and determine what needs to be fixed.

Read Full Q/A … : My car is spitting coolant from the overflow tank

I just got an oil change, but smoke is coming from under the hood of my car where my coolant tank is? Do I need more coolant?
ANSWER : Hello.

If the smoke is coming from the coolant tank then it may actually just be steam from the hot coolant, which is normal as long as the engine is not overheating. I would double check the coolant level though, just to make sure it’s correct. If the smoke is not coming from the inside of the bottle, but instead from around it, then oil may have been spilled on the exhaust during the oil change. The smoke would be from the oil burning off the exhaust. The exact location of the smoke needs to be determined first. If you need to have a mechanic look at it, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your smoke issue.

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I put the wrong key in my car and a few weeks later my car just shut down and it will not start I believe it’s the computer but…
ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you

Read Full Q/A … : My car is spitting coolant from the overflow tank

Eric smoalih

I am a certified master technician with the National Institute for Automotive Service Excellence (ASE), and I have been working as an auto mechanic for over 15 years. I am passionate about my work, and I take great pride in helping people keep their cars running smoothly.