Can I drive a car with a leaking head gasket?

Not recommended. A leaking head gasket can allow coolant and oil to mix, cause overheating, and lead to costly engine damage; if you suspect a leak, pull over safely and arrange roadside assistance or a tow to a shop as soon as possible.

What a head gasket does and why leaks happen

The head gasket sits between the engine block and the cylinder head, sealing in the combustion chamber and separating coolant and oil passages. When it leaks, combustion gas can escape into the cooling system or oil passages, and coolant can enter the cylinders or oil can become contaminated. Leaks can occur from age, overheating, improper installation, or warping of the cylinder head or engine block. Symptoms include overheating, white smoke, coolant loss without obvious external leaks, milky oil, poor engine performance, and abnormal exhaust or bubbles in the coolant reservoir.

Is it safe to drive with a leak? A careful assessment

In general, driving with a head gasket leak is risky. Short, careful movements to get to a repair facility might be possible if the engine is not overheating and you monitor temperatures closely, but even a small leak can worsen quickly and cause severe damage, including engine misfires, hydrolock, warped heads, or seized bearings.

When you might consider moving the car briefly

There are exceptional cases where you might need to move the car a short distance (for example, to reach a safe location or a tow pickup point). If you must do so, keep engine temperatures in the green, drive gently, avoid high speeds or loads, and be prepared to stop if the temperature gauge climbs. Do not drive long distances.

Immediate steps if you suspect a head gasket leak

Follow these steps to minimize risk and protect engine after a suspected leak.

• Do not drive the vehicle any farther than necessary. If safe, get the car to a safe place and arrange tow.


• Turn off the engine and avoid running it if overheating is evident. Do not open the radiator cap when hot.


• Check coolant and oil levels when the engine is cool and note any milky oil or sweet coolant smell.


• If safe, inspect for visible leaks around the head gasket area, radiator hoses, and water pump, but do not touch hot components.


• Call a tow service or roadside assistance to transport the car to a mechanic for a proper diagnosis.

After the vehicle is at a shop, a technician will typically perform compression or leak-down tests, inspect oil and coolant for contamination, check exhaust moisture, and review cooling system pressure to confirm a gasket leak and assess damage.

Repair options and what to expect

Repair costs and approaches vary with vehicle type and damage extent. A minor external leak might be addressed with a gasket replacement, while an internal leak often requires head removal, machining or replacement, and may reveal additional issues (warped heads, cracked block, damaged rings). Expect significant labor time and costs, often in the range of a few thousand dollars in many vehicles. In rare cases, severe damage might render the engine unrecoverable and require engine replacement.

Additionally, after a gasket repair, you may need to flush cooling and lubrication systems, replace the oil and filter, and monitor for recurring symptoms. It’s important to address root causes, such as overheating or head warping, to prevent recurrence.

Summary

Driving with a leaking head gasket is a high-risk choice that can escalate into serious engine damage. The prudent course is to stop driving, secure safe transportation to a repair shop, and have a qualified mechanic diagnose and repair the issue. While emergencies may demand brief movement for safety, do not drive long distances or continue driving with symptoms like overheating or rising temperature, white smoke, or milky oil. If you suspect a leak, act quickly to protect your engine and finances.

How do you temporarily fix a head gasket?

A temporary head gasket fix involves using a chemical stop-leak product poured into the cooling system to seal small leaks. This is not a permanent solution and requires a clean cooling system, specific application steps like running the engine at idle, and may not work for large leaks. While this can provide a temporary solution to get a vehicle back on the road, a professional repair is necessary for a lasting fix.
 
This video demonstrates how to use a head gasket sealant product: 56soxmanagainYouTube · Sep 14, 2017
Steps for a temporary fix with a stop-leak product
This video shows how to apply a head gasket sealant product with a turkey baster: 58sChrisFixYouTube · Oct 18, 2021

1. Clean the cooling system: Flush the old coolant and refill the system with a fresh 50/50 mixture of coolant and water. 
2. Remove the thermostat: To ensure the sealant circulates properly, remove the thermostat from its housing before sealing. 
3. Add the sealant: Pour the head gasket sealer into the radiator, following the manufacturer's instructions for the correct amount. 
4. Run the engine: Start the car and let it idle for at least 30 minutes to allow the product to work. Some products may recommend driving for a shorter period instead. 
5. Cool down and re-evaluate: Shut the engine off and let it cool down completely. Some procedures recommend repeating this process multiple times. 
6. Finish the repair: After the final cycle, allow the system to cool overnight. Then, reinstall the thermostat and spark plugs. Drive the car gently for the first 100 miles. 

You can watch this video to learn how to apply a head gasket repair kit: 53sMrSubaru1387YouTube · Nov 19, 2023
Important considerations

• Cleanliness is key: The cooling system must be clean before adding the sealant, as a dirty system can prevent the product from working correctly. 
• Not a permanent solution: These products are temporary fixes and will not repair severe head gasket issues. They are intended to last until a proper repair can be made. 
• Risk of clogging: There is a risk that the sealant could clog other parts of the cooling system, such as the radiator or heater core. 
• If the engine can't run: If you cannot run the engine for at least 15 minutes without overheating, the leak is likely too large for a sealer to be effective. 
• Professional repair: A permanent solution requires replacing the head gasket, which may also involve resurfacing or replacing the head itself if it's warped. 

How long can you drive with a leaky head gasket?

You can drive with a leaky head gasket for a very limited time, and it's not recommended, as the duration depends on the severity of the leak. A tiny leak might last for weeks or even months if you constantly monitor and top off the coolant, but a severe leak can cause engine failure in a matter of days, potentially leading to significant, costly damage. 
Short-term driving (a few days to weeks)

• Minor leaks: If the leak is small and only causes a slow loss of coolant, you might be able to drive for a while if you are diligent about checking and refilling the coolant. 
• Keep an eye on it: Continue to check your coolant level frequently and add more as needed. 
• Be prepared for poor performance: The engine will likely lose power and may not idle or run smoothly. 

What to avoid

• Don't ignore it: A small leak can quickly turn into a major problem, leading to more extensive engine damage if not repaired. 
• Don't drive long distances: Driving long distances with a head gasket leak can cause further damage to the engine. 
• Don't let it overheat: A head gasket leak can lead to overheating, which can cause the engine to crack or warp. 

This video explains how to test your truck for a leaky head gasket: 23spowerstrokehelpYouTube · Feb 12, 2013
Serious consequences

• Internal engine damage: If coolant leaks into the cylinders, it can cause the engine to overheat and damage pistons, valves, and other components. 
• Lubrication failure: If coolant mixes with the engine oil, the oil's ability to lubricate is compromised, which can lead to catastrophic engine failure in a very short time. 

This video explains what happens when a head gasket fails: 56sAuto V Fix YouTube · Nov 1, 2022
When to stop driving immediately

• If coolant is mixing with oil: This is a serious sign that you should not continue to drive. 
• If the engine is overheating frequently: This indicates a severe leak that needs immediate attention. 
• If you notice significant power loss or rough idling: These symptoms suggest the leak is severe enough to cause damage. 

What happens if your head gasket goes while driving?

Driving with a blown head gasket can lead to severe engine damage, including overheating, loss of power, and internal component failure. It can also cause the engine block or cylinder head to warp or crack, leading to costly repairs or the need for an engine replacement. It is strongly recommended to stop driving the vehicle immediately if you suspect a blown head gasket to prevent further damage.
 
You can watch this video to learn what happens to your car when you drive with a blown head gasket: 1mMercie J Auto Care, llcYouTube · Jun 7, 2021
What happens when you drive with a blown head gasket

• Engine overheating: A blown head gasket can allow hot combustion gases to leak into the cooling system, causing the engine to overheat rapidly. 
• Loss of power and poor performance: The engine will lose compression, leading to a noticeable drop in power and reduced fuel efficiency. 
• Contamination of fluids: The gasket is supposed to keep oil and coolant separate. When it fails, oil can mix with coolant, creating a milky substance, and coolant can leak into the oil or combustion chambers. 
• Internal damage:
  • Erosion: Combustion pressure leaking into the radiator can create acid that degrades cooling system components like the water pump and radiator. 
  • Component damage: Coolant entering the cylinders can cause broken or warped pistons and valves. 
  • Catalytic converter damage: Coolant passing through the exhaust system can damage the catalytic converter. 
• Increased risk of severe failure: Continuing to drive can cause more extensive damage to the cylinder head and engine block, making the damage irreversible and requiring more expensive repairs or a complete engine replacement. 

What to do if you suspect a blown head gasket

1. Pull over and stop driving immediately: Do not continue to drive the vehicle to prevent further damage. 
2. Allow the engine to cool down: This is especially important if the engine has been overheating. 
3. Check the coolant and oil: Look for signs of mixing, such as a milky residue on the oil cap or milky coolant in the reservoir. 
4. Schedule a diagnostic: Have the vehicle towed to a mechanic for a professional diagnosis and repair as soon as possible. 

Is a leaking head gasket worth fixing?

Still having trouble deciding whether fixing your head gasket is a good investment? Here's a rule of thumb: Only replace the head gasket if the vehicle is worth at least double the cost of the repair. If it's not, you're likely better off getting a new (to you) car.