8 Causes of Car Smells Like Antifreeze but Not Overheating


Antifreeze is the ingredient in engine coolant that prevents it from freezing under cold temperatures and prevents it from boiling during sunny days. If the antifreeze or engine coolant leaks out, it’s a matter of time before it overheats. But what happens if your car smells like antifreeze but not overheating?

antifreeze smell but no leak

Failures in the cooling system can cause severe engine damage if not addressed on time. According to the U.S. Department of Transportation, cooling system failures are the major causes of engine breakdown on highways. Here at Vehicle Fixing, we not only guide you on how to fix your car at home, but we also give you tips on how to prevent issues from happening.

What Does Coolant Smell Like?

Coolant has a sweet, warm smell and is easily recognizable. Engine coolants have sweet smells because of the ethylene glycol or propylene glycol used in formulating them. The sweet smell varies depending on the type of coolant used in your car since the manufacturers ingest other chemicals when producing them.

However, you should also know that while engine coolant has a sweet smell, it can be toxic if swallowed or ingested. So, keep it away from children and pets.

Car Smells Like Antifreeze but Not Overheating — Why?

Generally, a car smelling antifreeze means you have an underlying problem in the cooling system. If you perceive this smell and the engine is not overheating yet, the problem is at its early stage, and you can fix it without spending much.

Car smells like coolant but not overheating is a clear indication that the antifreeze is leaking somewhere in the cooling system. Even if there is no visible outflow, the antifreeze smell indicates a leak — it could be an internal or external seepage.

Let’s highlight where this leak could come from for easier troubleshooting and fixes.

The Heater Core

The heater core is a small radiator that warms the car cabin using heat from warm engine coolant. The Cooling system circulates coolant through the heater core as it circulates through the bigger radiator behind the front grille. As the hot coolant passes through the heater core, the heater motor blows warm air into the cabin.

If there’s a crack in the heater core, you will perceive antifreeze in the cabin as the heater motor blows the warm air. This antifreeze smell in the car happens because the motor blows the antifreeze along with the warm air.

External Coolant Leak

Another reason for smelling antifreeze in a car could be external leaks from the radiator, hose, or anywhere in the cooling system components. You may be smiling in disbelief, but believe it or not, not all coolant leaks cause engine overheating unless the coolant gets to a certain threshold. Luckily, it’s easier to identify a leak because you will see puddles underneath your vehicle.

Defective Radiator Cap

The radiator cap is designed to seal the neck of the radiator filler to prevent coolant from escaping and air entering the system. If the cap becomes weak, it cannot handle the pressure inside the radiator. If that happens, the engine coolant will escape as vapor.

Using a misfit radiator cap can be the cause. Replacing the cap could be all you need to fix the problem.

Cracked Coolant Reservoir

A common possible reason the cars smell antifreeze but no leaks is a cracked coolant reservoir. If the coolant reservoir is broken or cracked, the vehicle will emit a sweet smell from the engine bay. It could be the hose not tightened correctly, the cover is not tight, or the hose is torn.

It is a common issue but easy to fix. Inspect the hose connected to the reservoir, the cap, and the entire body for leaks. Retighten the hose if it is loose, change the cover if it is not tightened correctly, and replace the reservoir if it is cracked or broken.

Lousy Water Pump Seal

The water pump seal is an essential part of the cooling system that prevents water leakage and air ingress to the engine. It is installed on the water pump. If it wears out, it will cause coolant leaks and could be the cause of the antifreeze smell you perceive from the cabin.

If you suspect this seal is bad, look around the water pump area for damp marks and signs of leaks. At an early stage, the leak may not be big enough to form puddles underneath the car. If the seal is the culprit, replace it with a new one. Also, check the condition of the water pump and change it if necessary.

Broken Thermostat Housing

Another reason you perceive the antifreeze smell in a car is broken or cracked thermostat housing. This is true because a broken thermostat housing can leak antifreeze on a hot engine part, causing a burnt antifreeze smell you perceive while driving. You can address this by inspecting the thermostat casing and replacing it if it is broken.

Internal Leak

An internal leak is a common reason for a car smelling antifreeze, but there are no leaks. An internal leak means the coolant is leaking but not outside the engine. When this happens, you won’t see puddles underneath the car or in the engine bay.

However, you can quickly tell the coolant is leaking because it will require you to top it up more than usual. Often, internal coolant leaks go into the crankcase. If you check your engine oil and see a milky substance on the dipstick, you likely have coolant in the oil.

Broken Head Gasket

Coolant smell in a car, but no leak can stem from a broken head gasket. If coolant leaks from a blown head gasket, you won’t see any coolant puddles on the ground or around the engine, which makes it difficult to diagnose.

However, you can tell if you have a blown head gasket by looking at the white smoke under hood or from the tailpipe. A car with a blown head gasket will emit white smoke as the engine runs. White smoke from the tailpipe shows that something aside from fuel is being burnt in the combustion chamber.

Aside from fuel, another thing that can get burnt in the combustion chamber is engine coolant. The only feasible solution here is to replace the gasket.

How to Fix Coolant Smell in Car

Since there are several possible reasons your car smells like coolant but not overheating, there are several things to look into for proper diagnosis before fixing it. I have outlined them in simplified steps.

Examine the Exhaust Smoke

Start the engine and let it idle for 10-15 minutes.  Watch the exhaust smoke as the engine is idling. If excess white smoke steams out or coolant comes from the tailpipe, it shows something is wrong with the system.

Check the Motor Oil Level

Pull out the dipstick and check the oil level to see if it is below or exceeds the average level. If the oil level is below the expected level or exactly where it should be, you don’t have any internal leaks. But if the oil exceeds the average level, inspect the dipstick to see if it has a milky substance, which shows coolant is mixing with the engine oil.

You can tell if there is coolant in the motor oil by smelling or touching the oil on the dipstick. If there is coolant in it, the oil will have a sweet smell and be very light or muddy, depending on the amount of coolant in it.

Open the engine oil filler cap to see if there are white substances on the internal engine components to confirm you have an internal coolant leak. If the motor oil is mixed with coolant, you likely have a blown head gasket that needs replacement. Changing the head gasket will address the internal leak. Contact your mechanic to replace the blown head gasket.

Inspect Your Engine Bay

Check if smoke is steaming from your engine bay. If you see smoke spewing from the engine bay, identify the color of the smoke. If it’s white, there is a high chance your coolant is leaking. Examine the engine components I pointed out in this article, such as the water pump seal, thermostat housing, coolant reservoir, and radiator cap.

If you see engine coolant in these areas, you have identified the root cause of the problem. Repair or replace it as needed.

Final Words

The heater core, loose radiator cap, cracked coolant reservoir, broken thermostat housing, and internal coolant leaks are the common reasons your car smells like antifreeze but not overheating.

Now, you know why your car smells like coolant and how to trace and rectify the underlying problems. Fix the problem before it escalates. However, as I always say, if you don’t trust your gut in diagnosing and fixing this issue, consult your mechanic—they are trained to troubleshoot and fix car problems.

Solomon Osuagwu

Osuagwu Solomon is a vetted auto mechanic with over ten years of experience in the garage and five years of experience as a service writer. He prides himself in writing accurate information on professional repair guides, DIY repair guides, buyer’s guides, comparisons, and car reviews. If he’s not in his repair garage, he’s writing automotive blogs to help car owners and fellow mechanics to troubleshoot and proffer solutions to several car problems.

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