Your internal combustion engine can create an immense amount of heat and pressure when burning gas or diesel.
Gasoline engines can produce up to 700 pounds per square inch of pressure inside the cylinder, while diesel engines can produce up to 2,000 pounds per square inch. That heat and pressure must be kept inside the combustion chamber, between the cylinder head and engine, and the head gasket keeps it all sealed inside.
Beyond containing the combustion process, the head gasket keeps coolant flowing in the proper areas for consistent temperature and oil flowing for proper lubrication. If the head gasket fails, fluids can mix and the combustion process could be disturbed.
Table of Contents
It’s a big deal, so we’ve gathered the top 8 most common issues with head gaskets, how to identify and diagnose a problem, and how to fix it.
#1 – Your Engine Fluids Are The Wrong Colors
When you look inside your coolant overflow bottle or inside a radiator, your coolant color will most likely be green, orange, blue, or pink depending on what brand of coolant you have or what automotive brand you drive. Coolant should have a sweet smell due to the propylene glycol in the mixture. Engine oil on the other hand should be somewhere between a golden brown and a dark brown. Check also my walk-through of common reasons for excessive oil consumption.
Oil at the end of its useful life can turn black.
If you notice that your coolant is a dull or muted color instead of a bright contrasting green, pink, etc., you may have an issue with a head gasket. Your fluid colors should be distinctly different; if they appear to be mixed, a head gasket seal may have been broken.
How to Fix It
Your first step to fixing the issue is understanding if you really do have a problem or something as simple as aged fluid ready for a maintenance cycle. If you suspect you have a blown head gasket, take your time diagnosing the problem. Most local auto parts stores have a rental program for tools that can test for proper cylinder compression and if the combustion chamber holds pressure over time.
There are also testing kits to help determine if a fluid is mixed with something else, such as coolant and oil. Determine if there is a potential problem before seeking help from a mechanic or completing an expensive repair yourself.
#2 – Your Engine Oil Has Become A Frothy Latte
Your engine oil should not have bubbles or a frothy consistency like a latte (coffee).
If you remove the oil filling cap on the valve cover or remove the valve cover itself, you should not see a frothy oil mixture resting in the engine. If you have this condition, your coolant may be leaking into the engine oil and mixing.
How to Fix It
If you suspect that your oil has engine coolant in it, start by diagnosing the problem with the engine cylinder compression test and a cylinder leak-down test. These two testing methods can indicate if the head gasket seal at the combustion chamber has been damaged.
If the tests show that the combustion chamber holds proper pressure, there may be another area with a gasket failure allowing the fluids to mix.
Some intake manifold designs have coolant flowing through them that can mix oil and coolant, so it will be a step-by-step process to find the gasket that is leaking.
#3 – Your Engine Coolant Is Slowly Turning Into Mayonnaise
Your coolant should have the fluid consistency of water. If you have mayonnaise in your coolant overflow bottle or under your radiator cap, you may have engine oil mixing into your coolant.
How to Fix It
The head gasket seal is just one area where coolant and engine oil flow near each other.
Start with the compression tests as your first step in the diagnosis. There are additional places beyond the cylinder head where coolant and oil are near each other. Manufacturers may route engine oil through the radiator for additional oil cooling, and radiators can leak causing the fluids to mix.
Once you find where the fluids are mixing, it may be a simple fix that you can do at home with basic hand tools. If the fix is something major, such as a complete head gasket change, it may be the right time to take your car to a professional mechanic to complete the work.
#4 – Your Car Consistently Overheats
If your car consistently overheats, it may have a head gasket problem. Your cooling system is meant to be a closed system without leaks or pressure losses. Your radiator cap assembly has an internal spring that maintains the maximum cooling system pressure, which is usually between 15-20 psi.
A head gasket leak around the combustion chamber may allow heat and pressure from the combustion process to enter the cooling system while the engine is running.
The added heat and pressure can push the radiator cap beyond its pressure limit, and you may be losing coolant into the overflow bottle.
How to Fix It
To diagnose this problem, you can do the same cylinder compression tests as before. These may or may not indicate a problem concerning the cooling system. If you are consistently finding more coolant in the overflow bottle, it could be the radiator cap allowing coolant to leak by. You can replace it if it is a problem, but there are other signals that may prove it is innocent in this issue.
If you see bubbles in the overflow bottle while the engine is running, there is a pressure problem with the radiator cap holding the pressure in the system.
The definitive way to determine the cause is by testing the coolant for exhaust gases. If the coolant tests are positive for exhaust gas contamination, you know the head gasket is leaking exhaust into the cooling system.
Once you know whether the radiator cap or the head gasket is the problem, you can decide which to replace. The radiator cap is simple to replace, but the head gasket may be more than you want to tackle.
#5 – You Find An Oil Or Coolant Leak Near The Cylinder Head
The head gasket is located between the engine block and the cylinder head.
It seals the surfaces between the block and head, and it keeps fluids from leaking externally of the engine. If you find a few drips of coolant or oil, your head gasket may have developed a leak.
How to Fix It
Low mileage engines are easier to find leaks because they are very clean on the exterior surface.
High mileage engines are usually very dirty and can be harder to find the source of a leak. There are dyes that you can pour into your fluids that can be visible under a black light that can help investigate the source of a leak. Once the leak has been found, you can fix the gasket or surface that is allowing the leak to occur.
#6 – Your Exhaust Gas Contains Blue Smoke
Blue smoke from the exhaust pipe is an indication that oil is entering the combustion chamber and being burned in the combustion process.
How to Fix It
There are multiple ways that oil can enter the combustion process.
A leaking head gasket is just one of them. Worn piston rings, scored cylinder walls, cracked valve stem seals, and a faulty PCV system can also contribute to oil entering the combustion process. The PCV system should be external to the engine, and the easiest to diagnose for a problem. The valve stem seals require removing the valve cover, but they may not visually appear to be at fault.
The valve seals may require disassembly as well as the other potential causes.
At that point, it may be necessary to remove the cylinder head completely and look at all potential causes thoroughly before moving forward with a fix.
#7 – Your Exhaust Gas Contains White Smoke
White smoke from the exhaust pipe indicates you are burning coolant in the combustion process. Coolant isn’t flammable, so it may also cause a misfire in one or more cylinders on start-up.
How to Fix It
Coolant flows through the engine block and cylinder head to keep a constant temperature in all components. Coolant may also be flowing through your intake manifold. First check if there is a leak in the intake manifold that could be allowing coolant into the combustion process. If there is no apparent leak, then you can assume coolant is leaking between the engine block and cylinder head.
From there, the only permanent fix is to remove the cylinder head and replace the gasket.
#8 – You Have A Misfire Between Cylinders But No Smoke From The Exhaust
The combustion chamber on every cylinder should be sealed and isolated from the coolant and oil, and from every other cylinder in the engine block.
If the head gasket is damaged between cylinders, you may notice a misfire in two cylinders that share the same cylinder head.
How to Fix It
The process to diagnose if cylinders are leaking should be to test the compression on each cylinder and how much they leak over time. If two cylinders are leaking because of a gasket failure between them, both will have poor compression and leak test results.
The only permanent fix is to remove the cylinder head and replace the gasket with a new one.
Each of these fixes mentioned is meant to be a permanent repair. There are pour-in liquids that can temporarily fix a leaking head gasket, but we don’t recommend them unless it’s an emergency. These liquids can stop a head gasket leak in certain circumstances, but they can also cause additional problems.
Coolant additives can cause radiators to become blocked. Oil additives can restrict oil flow in the engine or in external oil coolers leading to reduced lubrication. Be cautious if you choose to use a temporary solution as it may add additional work later.