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Can a Bad Radiator Cause No Heat? (All You Need to Know)

A bad radiator meaning a faulty or damaged radiator may not produce heat. This can be caused because of a number of different reasons and naturally the worse the damage is the less heat it will be able to emit. If you are facing these issues, it is time to take a look inside the radiator.

Bad radiator cause no heat

A bad radiator can be the cause behind no heat coming out of the heater. A failure in the radiator will most likely cause the heater to become overheated which results in excessive pressure and temperature on the heater core causing it to break. Ultimately, heat can not be produced or emitted.

Now, to understand why radiators cause cold air with no heat, we must look at one of the most common causes of this problem. The wrong level of coolant which is a mixture consisting of water and antifreeze usually causes this to happen. When coolant level is lower than sufficient, it fails to support the heat production and this causes cold air to blow out of the heater with little to no heat.

This is not the only cause for no heat though. There are a few other problems that cause no heat to be produced. If your coolant level is fine, you might want to explore those.

Can a bad radiator cap cause no heat?

A bad radiator cap can be the culprit that is causing no heat. In order to understand why that happens, it is important to get an idea of the radiator cap’s mechanism. The radiator cap’s function is to properly regulate the pressure in the cooling system, it does this by working as an escape valve to let out pressure if it gets too high.

But if it is left in the open position, it fails to do its job which causes there to be insufficient pressure in the system. Therefore, the coolant can not get hot enough to supply the right amount of heater output. Due to this reason a radiator cap needs to be checked if you notice no heat is coming out.

Can a clogged, cracked and leaking radiator cause no heat?

A clogged, cracked and leaking radiator will not be able to give off any heat. When the cooling system and the heater core become clogged this evidently leads to a lack of heat that is usually present inside the system. This occurs because the hot engine coolant is unable to pass through the heater core due to the clogged radiator. When a radiator gets clogged, 9 out of 10 times this leads directly to a leak because a clogged radiator will make it hard for coolant to circulate in the radiator which ultimately leads to the coolant leaking into other parts of the engine of the vehicle.

Now let us see how a cracked radiator affects heat. A radiator is required to help prevent the engine from overheating but if it is cracked, the sufficient amount of coolant is unable to reach the engine which causes the engine to get overheated and it disrupts the production and emission of heated air.

3 reasons why a bad radiator cause no heat

A bad radiator translates to a radiator that is unable to function properly but why is that happening? We will be unable to understand this if we look at the radiator as one and just label it as a bad radiator, we must look at the individual parts within it and locate the problem. Here, we have listed some common causes that make a radiator a bad radiator that causes no heat.

Low coolant:

If the coolant level is low then it is natural that the radiator will not be blowing hot air. The coolant in the system might get reduced due to a leak or even water evaporation.


If the thermostat is left stuck-open then this will stop the engine and coolant from heating up and if they are unable to heat up, they will not be able to produce and supply heat.

Water pump:

If there happens to be a problem with the water pump of the engine then it is likely that no heat will come out because a bad water pump will prevent the coolant from traveling smoothly through the engine block, hoses and radiator which will cause overheating during summer months and freezing during winter.

What are the signs of a bad radiator causing no heat?

When you notice that no heat is blowing out, sometimes it does not even register that the radiator is causing this. Next time when the heater is acting funny and leaving you shivering in cold, look for these signs we have noted down below to determine if the radiator is causing this.

Sign 1:

The first and most obvious sign that your radiator is failing at performing its task is when you notice the heater has stopped working. This is the first clue that you need to have a thorough check of the radiator.

Sign 2:

If you begin to notice that the temperature gauge needle is always indicating that it is running hot then clearly there is a problem with the radiator. This usually means that the cooling system is unable to work properly as the coolant can not reach all the places it needs to in order to keep the engine cool thus causing overheating.

Sign 3:

Another very hard to miss sign is when steam begins to billow out from the bonnet of the car. This occurs because when the temperature gauge begins to heat up the engine of the car will follow suit and begin to overheat as well.

Sign 4:

As we have discussed at length already how coolant affects the radiator, you will have to look inside the radiator to check the coolant. If you notice that the coolant level is lower than usual or is starting to leak out then you have a problem. You should also be able to tell the condition of your radiator from the color of the coolant, usually it is either translucent, yellow, green or red in color. However, if you notice that it looks brown like rust or oil with a consistency similar to that of sludge then this is worrisome.

Sign 5:

Another unlikely sign that points toward issues in the engine is when you start to have trouble shifting. If you notice difficulty shifting, it can be caused due to the fluid becoming contaminated with coolant that has leaked out through the cracks and other faults.

How much does it cost to fix a bad radiator causing no heat?

In general, it costs anywhere from $200 to $900 to fix or replace a bad radiator that causes no heat. This is however only an estimation as the price can differ depending on which part you are fixing or are you getting the entire thing replaced with a new radiator. There is also the question of the vehicle’s make and model as they tend to effect the price of fixing a bad radiator as well.

Some vehicles fixing and changing a bad radiator can cost somewhere between $400 or $500 while the vehicles that come with a radiator that has aluminum core and plastic will cost $100 to $600 to fix or replace depending on what you need.

How to fix a bad radiator?

Professionals do a fantastic job at fixing bad radiators but the price can be out of budget for a lot of people but that does not mean it is okay to drive around with a bad radiator because the problems that seem miniscule today can begin to damage other parts of the engine outside of the radiator. So, if it is hard to afford or if you want to try fixing your bad radiator by yourself then you can follow the step by step guide we have provided below for you.

Step 1:

You will need to begin by looking inside the radiator and around it to spot any cracks that might be causing coolant to leak.

Step 2:

If you are certain you have located the leaks and are sure they are causing the no heat problem then use some stop-leak product such as the AlumAseal Radiator Stop Leak & Conditioner and pour it in the radiator. It will quickly and very effortlessly fill up the small cracks and holes.

Step 3:

After you are done filling up the leaks, check the coolant level and make sure it is at optimal level.

Final Thoughts

A bad radiator can certainly be the reason that is causing no heat. If all the signs point that the radiator is at fault then take a look inside and fix the problems you see such as leaks or coolant levels but if you are unable to fix it at home, take it to the repair shop instead.