Engine Overheating and Smoking: Understanding The Causes & Fixes

Last Updated on May 10, 2024 by Azim Uddin

Every car’s engine is built to operate within a certain temperature range. Even so, it is not uncommon for the engine to overheat. This happens when one of the cooling system’s components becomes faulty, including the radiator, thermostat, and radiator hoses.

But what does it mean when you experience engine overheating and smoking at the same time? If the car overheats and produces smoke, it signifies you have a coolant leak. This can be caused by a blown head gasket, damaged radiator, and hoses, or cracked block and cylinder head. The culprit could also be an engine oil leak.

Facing the same overheating and smoking problem? We implore you to read our comprehensive guide below.

What Causes Engine Overheating and Smoking?

A coolant leak is the common cause of engine overheating while also smoking. This is because coolant fluid plays a critical role in regulating the engine’s temperature.

So, when it leaks and gets too low, it will not provide enough cooling, causing the engine to overheat. As the coolant leaks, it can come in contact with the hot engine components and burn, producing white smoke. The smoke is usually accompanied by a sweet smell.

As it turns out, there are several causes of coolant leaks, leading to the engine overheating and producing smoke. These include the following.

1. Blown Head Gasket

The head gasket has many roles, including sealing the combustion gasses and preventing coolant leaks into the cylinders. This helps ensure the engine does not overheat.

So, when it blows, coolant could leak into the combustion chamber, causing the engine to overheat. As the coolant burns, you will notice a big cloud of smoke coming from the exhaust.

Some signs of a blown head gasket include engine misfires, bubbles in the radiator, and coolant beneath the gasket.

Solution

A blown head gasket can only be replaced and not repaired. However, the replacement job is not for the average do-it-yourselfer as it involves dismantling the engine. Therefore, you should let a qualified mechanic help you.

Below is a detailed video of how to replace the head gasket if you would like to try:

2. Cracked Block or Head Cylinder

If the engine block or head cylinder has cracks, coolant will leak, preventing it from circulating through the engine. The leak can be internal or external. As a result, the engine will overheat.

As the coolant drips onto the hot points of the engine, it will burn and produce white smoke from under the hood.

To diagnose a damaged block and head cylinder, check for clear signs of damage or cracks. In addition, look for visible coolant leaks around the block.

Solution

There are multiple solutions to a damaged engine block or head cylinder. The day-to-day techniques include:

• Welding

This solution involves melting the surrounding metal and filling the cracks with filler rods and molten metal. There are two typical welding techniques, including furnace and flame spray welding.

• Pinning

Pinning involves piercing holes on both sides of the cracks and filling them with overlapping pins. It is a more affordable and fast solution compared to welding.

• Metal Stitching

Also known as metal locking, this is an effective method for repairing a cracked engine block that cannot be mended via welding. This is because, unlike welding, it is done cold with no heat to impact other engine components. Metal Stitching involves using metal locks.

However, all these solutions can only be implemented by a professional technician due to their complexity.

3. Damaged Radiator and Hoses

An automotive radiator helps protect the car from overheating by transferring heat from the coolant to the air. This cooling system component is connected to the engine via multiple hoses that allow coolant flow.

If the radiator or its hoses are cracked, coolant will leak, and the engine will not get cooled efficiently. As a result, the engine will overheat and smoke as the leaking coolant burns.

You can diagnose a cracked radiator or hose by lifting the car hood and checking for signs of cracks or sludge. To establish the exact source of the leak, your mechanic can perform a pressure test.

Solution:

For a cracked radiator, sand the crack and clean the area thoroughly. Then, apply epoxy resin or putty to seal the cracks. In the case of cracked radiator hoses, you can wrap insulating tape or duct tape around the hole.

However, if the radiator hoses are severely damaged, the best solution would be to replace them. Here is how to do the replacement:

• Step 1: Drain the coolant.
• Step 2: Release the clamps on the leaking hoses.
• Step 3: Remove the hoses by sliding them off.
• Step 4: Clean the hose fittings and apply a sealing compound inside the new fittings.
• Step 5: Place the clamps over the new hose ends and slide the hose into position.
• Step 6: Tighten the clamps and refill the coolant.

Does Oil Leak Cause Engine Overheating and Smoking?

Yes. Apart from a coolant leak, an engine oil leak can contribute to the engine overheating and producing smoke. The oil usually flows through the engine to lubricate all its components. Consequently, this helps reduce friction and prevent the engine from running hotter than usual.

So, when the motor oil leaks, causing the levels to decrease, lubrication also reduces. This leads to heightened friction and heat generation, causing the engine to overheat. And when the oil drips onto the hot engine components, it can burn and produce bluish-white smoke.

Typically, engine oil leaks can occur due to the following:

• A faulty oil filter
• Damaged oil pan or gasket
• Dried-out or cracked seals
• Loose drain plug.

Depending on the cause of the oil leak, the solution may include replacing the damaged component or retightening any loose parts.

FAQs

Before we conclude, let’s check out some frequently asked queries regarding engine overheating and smoking.

Can a faulty thermostat cause the engine to overheat and produce smoke?

A faulty thermostat stuck in the closed position will cause the engine to overheat by restricting coolant flow. However, it will not cause the car to smoke from the engine.

What should I do if my engine overheats and smokes?

You should immediately pull to a safe spot and turn off the engine. Then, allow the engine to cool down before checking the coolant levels and for leaks. After that, call a trusted mechanic for assistance.

Will a defective water pump cause the engine to overheat and smoke?

Yes, but indirectly. Generally, a faulty water pump will prevent coolant from being circulated throughout the engine, causing overheating issues. If the problem is not fixed, severe engine overheating can lead to a blown head gasket, causing a coolant leak and smoking.

Final Words

In most cases, your car will overheat but not smoke. However, a coolant leak is usually the number one culprit if the engine is overheating and smoking simultaneously. So, to fix the problem, you must find the source of the leak. Sometimes, an engine oil leak can also contribute to overheating and smoking. Therefore, proper diagnosis is crucial and could help you avoid severe damage to the engine.