4 Causes of car overheating with full coolant in reservoir tank
Car engine overheat may bring catastrophic damage to engine components and a huge cost to repair. Low coolant levels are the most common reason engines overheat. When steam erupts from your engine hood, this is a sign that your car is losing its coolant.
The simple act to do is to check the coolant level through the reservoir tank of the radiator or open the radiator cap to see the coolant inside the radiator. Please waits 1-2 hours to ensure the engine is cool. Don't open the radiator cap while it's hot. It is forbidden because it can cause severe injury.
Somehow, when we check the coolant, the reservoir tank shows that the coolant is full. At the same time, the engine was overheating. This article will give you information on four causes of car overheating with coolant full in the reservoir tank. See the detailed info below.
1. Radiator cap failures
The first cause of car overheating and coolant full in the reservoir tank is radiator cap failures. There are two main functions of the radiator cap, the first is to close the radiator filler hole, and the second is to maintain the pressure inside the cooling system.
When the radiator cap failures happen, it ruins the entire cooling system performance. Engine overheats and coolant full in the reservoir tank are the most cases will occur. Below are common failures that mostly happened in the radiator cap.
A. Missing or broken vacuum valve
The vacuum valve function draws coolant from the radiator reservoir tank when the cooling system is below the atmospheric pressure. Also, it prevents the coolant from flowing back to the reservoir tank when the cooling system pressure is higher than the atmospheric pressure.
A missing or broken vacuum valve will ruin its function. It makes the engine overheats. When the cooling system pressure rises, it pushes the coolant to flow out to the reservoir tank. The reservoir tank will overfly, and the coolant inside the cooling system will reduce.
B. Worn out or damage pressure valve gasket
Worn out or damage pressure valve gasket is also makes the car overheating and the coolant in the reservoir tank is full. The pressure valve on the radiator cap is used to keep the desired pressure on the cooling system.
When the pressure valve gasket gets broken or damaged, the pressure inside the cooling system will be lost and pushed the coolant to flow out to the reservoir tank. As a result, your reservoir tank will be full of coolant, and the engine will start to overheat.
C. Wrong radiator cap pressure value (lower value)
Wrong radiator cap pressure value can make car overheating with full coolant in the reservoir tank. Mostly, if you use the lower value from its specific recommendation from the carmaker.
Yes, radiator caps have many similarities in shapes and dimension even though the pressure value were stamped on the top of the radiator cap is different. If you choose the lower pressure value, then it cannot hold the pressure. As a result, the coolant will flow to the reservoir tank and make the engine overheat.
2. Clogged radiator
The next cause of car overheating and coolant full in the reservoir tank is from a clogged radiator. A clogged radiator will block the coolant flow to the radiator, so the coolant only flows inside the engine and can't cool down its temperature.
When the coolant cannot cool down its temperature, the engine will overheat. The coolant will flow to the reservoir tank because the cooling system is overpressure.
Read also:- What to do when car overheats?
- 5 Signs of clogged radiator
- How does a radiator cap work?
- Radiator Hose Function In Car Engine
3. Waterpump failure
The other causes of car overheating with full coolant is waterpump failure. The waterpump function is to pump the radiator coolant in and out of the engine. It makes the radiator coolant cirulates in the cooling system inside the engine.
For this case (car is overheating with full coolant), the blade/fan pump of the waterpump is missing because of rust. Take a look the image below when the waterpump missing its blade/fan pump because of rust.
The water pump on the right side has lost its blades because of rust. It makes no coolant circulation inside the engine. It also makes car overheat with full coolant. In addition to rust, water pump failure that can make car overheat with full coolant is waterpump fan/blade damage, broken, or wrecked.
4. Radiator motor fan failures
The last car overheating and coolant full in the reservoir tank is because the radiator motor fan failures. A Radiator motor fan is used to draw the fresh air to the radiator core pipes and fins so the heat inside the coolant can be released to the open air.
Radiator motor fan damage can occur due to various conditions such as blown fuses, motor failure, poor connections, malfunction of the fan controller, etc.
Suppose the radiator motor fan cannot work properly because of several conditions, as I mentioned before. In that case, the pressure inside the cooling system will rise over and push the coolant to flow to the reservoir tank. As a result, the car engine is overheating.