The head gasket is a fundamental part of a gasoline-powered lawnmower engine. It seals or separates the cylinder head from the engine block to prevent the mixture of coolant and oil. Also, it can seal in the internal combustion process. A faulty or blown head gasket may cause engine failure. With these role-playing

So, how to identify and repair if the lawnmower has a blown head gasket? You may see different changes if it doesn’t work properly. These are oil leaks, coolant consumption, blue or white smoke, and starting failure. Once these symptoms appear, you must change the head gasket or call the experts.

This discussion below will discuss the possible causes, effects, and solutions to the head gasket that causes lawn mower engine failure. I hope it helps you in lawn mower troubleshooting.

What actually is the Head Gasket?

A head gasket plays a vital role in an internal combustion engine. It can seal or separate the engine block and cylinder head to avoid combining the engine fluids. Again, it can prevent any pressure losses, which is why the lawnmower works improperly. If any leak is available in the head gasket, the engine may run poorly or get overheated soon.

Manufacturers use multiple layers of steel (MLS) to make the modern gasket more durable. The center layer is thicker, whereas two thinner outer layers can resist extreme heat and chemical reactions. Earlier, people used to use fiber head gaskets. But they were more prone to failure. But MLS gaskets are relatively more efficient and long-lasting.

Let’s talk about the problems and vice versa about the head gasket:

The lawnmower won't start after replacing the head gasket

You have changed the head gasket thinking everything will be fine. But it is not happening as the lawnmower is not even starting properly. The main reason it is happening is installing an incompatible or faulty head gasket. Also, you may haven’t installed it properly, or something is wrong, which you shouldn’t do.

If the lawnmower fails to start after replacing the head gasket, possibly the gasket itself is the reason. You should ensure that it is properly seated. Also, there should be no leaks. If the problem persists, it may be necessary to replace the cylinder head.

Another reason can be the fouled or damaged spark plug. It may not be firing in common ways. Check the gap on the spark plug and inspect the fuel line if it is clogged.

Sometimes pre-ignition can cause the replacement head gasket not to work well. If the engine combusts fuel very often in a single cycle of the engine, the cylinder head gets large pressure inside. Then, the engine starts working unwantedly, which may cause the head gasket failure.

Leaks of coolant from rusted or dodgy piping can be why the engine fails to start after replacing the head gasket. When it happens, the engine will get overheated, and the head gasket won’t control this.

How do I know if my lawnmower has a blown head gasket?

A lawnmower is like a magical device to maintain the lawn soothing our eyes. Its peak performance depends on several factors, and the head gasket is one of them.

Symptoms of a blown head gasket on a lawnmower

If the gasket is blown, you may see a lot of white smoke from the engine. Sometimes, the engine may fail to start, which signifies a damaged head gasket. When the gasket is worn out, it leads to low engine power.

There can be a leak of oil that may blow the gasket. You may run a compression test to diagnose a blown gasket. Also, you may use compression gauges to calculate the internal combustion pressure. For this, pull the started cord again and again. You may have a blown gasket if combustion chamber pressure is lower than 60 psi even after adding little engine oil.

A cracked head gasket, loose or missing bolts, compromised seals in the gasket can make the combustion chamber lose its vacuum seal. The released and sustained energy powers the pistons when gasoline is combusted in the chamber. But a blown gasket can cause reduced pressure and power from the combustion.

If you have an active lawn mower, all the head gasket seals are in the right shape. But the seals dry out after a certain time. Then, they become very brittle, and fluid leaks around the gasket. It is a symptom of a blown head gasket. You can temporarily fix the problem using a liquid sealant. But replacing the head gasket is the best solution.

When an engine overheats frequently, it may cause head gasket failure. On the other hand, a blown gasket seal can also cause the engine to overheat than the normal temperature. A blown tool can make passage for hot exhaust gases into the cooling system. Again, the coolant turns into steam when the gasket is blown and leaking the coolant towards the cylinders. As a result, the engine becomes hotter, and the lawnmower won’t start.

If you see milky sludge beneath the oil filler cap or on the dipstick, you can consider that the head gasket is compromised. The reason behind it is that the coolant leaks and mixes with oil. A replacement oil filter or engine oil flush can be a good solution.

You may follow these below steps too for knowing if the gasket is blown or not:

• First, check out all the general symptoms which I have explained above.

• Remove the engine cover and relevant items to access the engine properly.

• Separate all the complementary parts available over the engine.

• Identify the sparkplug position and unscrew it.

• Take necessary tools and disassemble the head of the engine.

• Find out all the scuffs, marks, or blows around the head.

• Identify if there are any carbon deposits of valves and pistons.

• Replace the gasket if it is blown; otherwise, reassemble the parts.

• Turn on the engine and check out if the lawnmower is working properly.

Why is my lawnmower cranking but not starting?

Cranking is generally the turn and starter power of any lawnmower engine. Usually, the flywheel spins around when you try to start the engine.

There are several reasons why your lawnmower cranks but doesn’t start. Here are some of them:

• A bad or no gas in the chamber is a reason for lawnmower failure. Maybe the gas is not fresh, or not enough gas in the chamber.

• Plug wire is off or loose enough that leads engine not working well.

• A faulty or wet plug can be why the engine fails to operate well.

• Not enough charge in the battery, or you haven’t changed the battery for a long time.

• You have forgotten to keep the air filter clean, which is also possible.

• You should set the manual choke to full to start a cold engine; otherwise, the engine will fail.

• You are not following a set procedure of the lock-out or safety sensors available in the mower.

• Some kinds of faults in the control module and coil system.

• A possible reason can be a fault at the engine compressor or valve sections.

How much does fixing a blown head gasket on a lawnmower cost?

If you are a beginner, you may need to spend 3-8 hours troubleshooting any head gasket of the engine. It includes the assembling and disassembling of the lawnmower engine. If you need to replace the gasket or other parts, it may require more money.

Average head gasket replacement requires $1620-$1980. This cost includes the associated labor cost (around $900-$1150) and buying new parts cost ($720-$830) on average.


The Head gasket of a lawnmower can keep the lawnmower at its peak performance. If the engine has a blown gasket, you should find out the reasons first. Then, repair the damaged part. Alternatively, replace the device for the best solution.

I have included all the reasons and signs of having a faulty or blown head gasket. You should prevent gasket failures which are better than curing them. After all, it will save your money and time together.