One day, you realize your antifreeze liquid is bubbling, and you don’t know why a coolant reservoir boiling but engine doesn’t overheat. Congratulations! You found the right place.
Our article offers useful information about the causes of this phenomenon and some solutions. Don’t hesitate anymore. Let’s scroll down to come nearer to your desired answer.
How Does A Coolant Reservoir Work?
The coolant reservoir is an essential part of the car’s cooling system. Its mission is to keep excessive coolant fluid until needed.
It’s a plastic bottle lying near the radiator. When you open the cloak, following the tube of the radiator, you can easily see it. The coolant fluid is only put into the reservoir.
Once your car’s engine heats up, the pressure in the radiator goes up. The radiator cap let some coolant liquid run into the reservoir to release pressure.
This fluid will stay here until the engine is cool enough to make negative force and pull this overflowing liquid from the reservoir back into circulation. The reservoir should be left with ⅓ of the coolant when your car is off.
Why Is A Coolant Reservoir Boiling But Engine Doesn’t Overheat?
The problem might be rooted from:
- A leaking or blown head gasket.
- An issue with the radiator cap.
- Faulty radiator fan.
- Old Coolant.
- Malfunctioning thermostat.
The Sign Of Bubbling In Coolant Reservoir
The antifreeze fluid performs in a sealed network of pipes that push it throughout the engine.
This concentrated liquid runs through many components such as cylinder heads, engine molds, and gaskets and keeps your car running at the appropriate temperature.
But, when air comes into this sealed system, it fights with the pressure, causing bubbling and blockages. Here are some symptoms proving that your coolant reservoir is bubbling:
- The engine power is decreased.
- Steam appears below the car bonnet.
- A hot smell escapes from the vents.
- The bonnet is too hot to touch.
- The engine sounds like boiling water because the engine oil becomes thin at high temperatures.
Main Causes Of A Radiator Boiling But Not Overheating
Leaky Or Blown Head Gasket
There are numerous gaskets in a car, but the head gasket is the most important. It is created to lock the firing pressure on the cylinder.
Moreover, this part also protects oil and antifreeze liquid from leaking into the cylinders.
A blown or leaky head gasket is a common trigger of bubbles in radiator. Once the head gasketleak exists, burning gasses from any cylinders slide into the water jacket, then push air into the cooling system.
Below are some signs of a bad head gasket:
- White smoke in the tailpipe.
- Bubbling coolant tank.
- Low level of antifreeze.
- Overheated car.
Faulty Radiator Cap
The radiator cap performs as a seal to retain pressure in the cooling system while allowing coolant flow in the expansion reservoir.
When this component is faulty or replaced with an unsuitable one, it will let air fly into the cooling system, causing a coolant reservoir tank boiling.
Here are some indications of a badradiator cap:
- Uneven pressure of the cooling network.
- Leaking antifreeze liquid.
- Boiling coolant fluid.
- Radiator pipe collapses.
Defective Radiator Fan
The radiator fan is one of the most vital parts of your car. Depending on the type of your vehicle, it may have one or two radiator fan systems.
The main function of this component is to cool down the antifreeze fluid. It is often attached to the radiator by a wire structure. Over time, these lines tend to corrode.
The radiator will overheat once the wires become weak as the fan doesn’t offer enough air circulation when your car stops.
Some symptoms of a defective radiator fan:
- A blown fuse.
- Damaged wires.
- Poor relay.
Contaminated/Low Coolant
You may know what coolant fluid is and its function – absorbing heat from your car’s engine. When the antifreeze liquid is old, its capability of keeping heat and carrying it to the radiator is weak.
When the coolant fluid is still used after 60,000 miles of consumption, it can result in a hot coolant problem.
Malfunctioning Thermostat
The thermostat is an essential factor in controlling the coolant temperature and managing fluid. When the engine becomes hot, this part opens for the coolant fluid to get into and decrease the heat.
However, this part sometimes doesn’t work well. It can lead to the situation that your reservoir is boiling and create some noises. Or it can make the coolant blow out of the reservoir.
How To Fix Coolant Boiling In Radiator
Replace Bad Thermostat
The thermostat is a vital part that controls the coolant temperature and adjusts fluid. Its mission is to regulate the antifreeze from the engine in and out of the radiator.
Hence it has to open and close at an accurate time.
However, a thermostat sometimes doesn’t work well. It’s time you know you have to replace it, or else your engine will be in trouble. We provide a guideline on how to replace it:
- Remove the antifreeze from the radiator.
- Open the hood, find the radiator cap and pull it out.
- Detect the thermostat and take it out. A 1/4-inch ratchet extension and a socket are helpful tools in this step.
- Add the new thermostat.
- Repeat the rest in a reverse way.
Supplant A Leaky Gasket
Because a leaky head gasket allows gas to come into the cooling system, you need to close the leak up. You should take your car to a professional repair store.
Another option is you reconstruct it with a leak repair liquid if you don’t want to spend too much money. Supplanting a leak head gasket in stores can cost you $1000 to $2000.
Yet, if you can fix it at home, the amount of money you have to spend is about $12 to $20.
The way of replacing it at home is quite easy. You need to add the sealant overflow reservoir when the engine is inactive at a normal temperature.
Replace The Radiator Cap
When the radiator cap is faulty, the pressure will fluctuate and let air fly in the cooling system. Hence, you need to supersede this component.
Make sure that you supplant it with an OEM or manufacturer-recommended cap. Don’t worry that you have to spend a lot of money like the head gasket situation.
The radiator cap is the cheapest component to replace. It’s about $5 to $25 for this part and $10 to $50 for the repairer.
Change The Radiator Fan
Our third suggestion for you is to replace the radiator fan. Below is the guideline:
- Open the hood and take the air filter out
- Unplug any electrical link to the radiator
- Unfasten the radiator
- Take the battery out
- Remove respectively the radiator’s pipe covering and pipe
- Put in a new fan
- Perform the above steps reservely.
Replace/Flush Coolant Fluid
The last advice for you is to change your antifreeze every 30,000 miles. But, if your car is a new model and this concentrated liquid hasn’t ever been replaced before, you can flush it after you drive for 60,000 miles.
Frequently Asked Questions
What is The Boiling Point Of The Coolant?
It is the point where antifreeze fluid boils while the pressure is retained in the cooling system. Depending on the types of coolant fluid, their boiling point is a little different from each other.
An ethylene-glycol-based coolant has a boiling point of 248 degrees Celsius, and that of a propylene glycol stands at 205 degrees Celsius. If the temperature cools down, your coolant liquid will start its job.
How To Prevent Coolant Reservoir From Boiling In The Future?
You can still prevent this issue by maintaining the cooling system.
It would be best if you replaced the coolant every two years and regularly kept an eye on the engine’s cooling system.
Final Words
To sum up, we have discussed the factors leading to a boiling coolant reservoir: blown head gasket, faulty radiator cap, defective radiator fan, low coolant fluid, and faulty thermostat.
We also explained to you the solution for each problem. Now, it’s your turn. Let’s detect the reasons for your issues and the way to fix them.
We hope this article can satisfy your question – why does a coolant reservoir boiling but engine doesn’t overheat?