You might think coolant leaks from the car when the engine is running, but that is not the case.
When the engine is running, the coolant circulates through the system and it is less likely to leak out. So what leaks coolant when the engine is not running?
In this article, I will discuss why the coolant may be leaking when the engine is not running, and I will show you some simple solutions.
Causes of Coolant Leak While Car is Running
When the car is not running, leaks can occur from bad hoses, a bad radiator cap, a bad radiator, or a bad water pump. It could also be a bad heater core or a blown head gasket. The leak could also be from a bad intake manifold gasket.
Now here is some more specific information about it leaking both when the car is running.
#1. Bad Heater Core.
The heater core is the part of the system that pumps hot coolant into the engine. When you turn on the heater, the heat generated from the system is blown into your vehicle through the HVAC vents.
If the heater core is bad, you will have trouble getting heat into the system, and you may also see leaking under the vehicle near either passenger or driver seat area.
#2. Damaged Hoses.
If your hose is broken it may leak when the engine is running or not running. As the motor is running the pressure of the system may increase the leak or decrease the leak depending on where the hole is.
Either way, hoses can become brittle and worn over time which is way they should be checked regularly. Heat and constant pressure can increase that wearing issue if you do not check it.
#3. Bad Radiator Cap or Radiator.
The radiator cap keeps the coolant in the system and holds the pressure in the radiator.
If the cap is broken, coolant will leak out and reduce the levels in your radiator. The coolant reservoir can overflow when you run the engine because of the higher pressure in the hoses.
If the radiator is cracked or damaged from any external damages, it can be from corrosion or stones if you are running your vehicle at higher speeds.
#4. Blown Head Gasket.
If coolant has begun leaking into the engine oil or combustion chamber, it is likely the result of a blown head gasket. The head gasket keeps the oil and coolant separate from each other.
When coolant leaks into the engine, it can no longer keep the engine cool which can happen when the engine is running and off, but running the engine is more dangerous because you won’t notice it until the motor starts overheating.
A bad head gasket can also result in external coolant leaks, and you may see if coolant leaks out between the engine block and the head.
#5. Defective Water Pump.
If the water pump is broken, you can expect a significant coolant leak. The purpose of the water pump is to move the coolant via the hoses as it should.
As the water pump begins to fail, the coolant cannot flow as it should. This is another situation that can lead to engine problems on and off.
#6. Bad Intake Manifold Gasket.
The intake manifold gasket is located at the junction of the engine and manifold. If fluid is leaking onto the ground beneath the vehicle, then the intake manifold gasket may be the cause.
Like any of the problems we have discussed, it is better to address as soon as possible. In other words, waiting to make this repair can turn into bigger problems for you as the engine operates normally.
Areas to Examine for Coolant Leak
#1. Radiator/Cap.
First, check the edge of the radiator for a leak. You might need to wash off the radiator of leaves, dirt and debris to see the leak better, if direction of the leak seems to come from that angle.
Also, check the radiator cap to see if it was damaged, and it was securely fixed in place to prevent a leak and other issues.
#2. Hoses.
There are hoses throughout the system to check. If there is a torn hose, the coolant should be “dripping” out of it. The leak only occurs when the engine is running or off and where the coolant is sitting, depending on how bad the hole is in the hose.
You will also want to check for cracks in the hose surface. Even if there is not a hole, coolant could easily be leaking out of the hose crack.
#3. Under Vehicle.
Get under the vehicle and take a real good look to see where the coolant is leaking out from. Depending on what kind you use, the liquid will be blue, red, or green.
Once you know where the leak is coming from, you will better understand which part may have failed. If you have been driving with the coolant leak, some of that liquid may have blown out onto other parts of the vehicle, making it difficult to identify the source of the leak.
Consider washing down the undercarriage and checking again at some point to help you understand where the leak is coming from.
#4. Heater Core.
Look at the floor boards under the passenger seat of your vehicle. If there are stains from some type of coolant, it is possibly coming from the heater core.
When the heater core goes bad, you can expect to see the fluid leaking under the car on that side. A leaky heater core will also cause a lower amount of coolant and may lead to overheating of the engine.
#5. Under the Water Pump.
Water pumps are typically driven from either the serpentine belt or timing belt depending on the model of your car. Starting with the serpentine belt version, you can, once again, look for leaks under the pump.
In a timing belt driven water pump, it might be a bit harder to see, and you’ll most likely have to remove the timing belt cover to get a view of the pump. However, if you see a leak under the crankshaft pulley and believe it is a timing belt driven pump, chances are it is leaking from the water pump.
#6. Head Gasket.
A leaking head gasket is not something you are going to see. You need to check the oil and coolant fluid to look for contamination; oil in the coolant or coolant in the oil.
You could also look around between the engine block and head to see if there are any external coolant leaks.
How to Fix Coolant Leak?
The fix for a coolant leak is dependent on the initial cause of the leak. For instance, if the heater core has a leak, the only course of action is to replace the defective heater core, which will range from $500-$1,000 for parts and labor.
Hoses that are leaking may vary in cost depending upon what hose it is and how complicated it is to remove. Sometimes the hose leaks because it has a loose clamp in the middle. If so, you can simply tighten or replace the clamp.
You can fix a leaking radiator cap, which is one of the cheapest options, for a cost of around $10-$50 plus the easy installation.
If the water pump goes bad, it will have to be replaced. A water pump replacement will run between $350 and $800, unless you buy a remanufactured water pump to save some money.
If the intake manifold gasket has to be replaced, the part doesn’t cost much, maybe only $20-$100, but it is very labor-intensive to replace, so labor could be another $200-$400 unless you can replace it yourself.
The worst-case situation is the head gasket. You could expect to spend between $1,500 and $2,000 for the new installation.
And if you don’t fix the blown head gasket quickly, you will develop a serious engine problem because the motor overheating will continue to damage the motor. This is a problem you cannot ignore.
Can I Drive With a Coolant Leak?
Your car may feel alright even with a leaking coolant, but don’t drive the car. When the coolant is leaking from the engine, the engine won’t be properly cooled.
An overheating engine can lead to irreversible damage. In addition, a small coolant leak can quickly turn into a big one – even when you are driving. For example, a small hole in a hose can turn into a big hole, where all your coolant is dumped out when you are not at home.