Whether you have a simple small engine on your push mower or a water-cooled engine on your riding lawn mower, you might run into an issue with your head gasket. Depending on your engine’s design, some of the symptoms might be different, but several of them will be the same. So, if your lawn mower isn’t running like normal and your usual fixes aren’t working, let’s look at the head gasket and see if that’s where the problem lies.
How to Diagnose a Blown Lawn Mower Engine or Head Gasket
A head gasket seals the head to the engine block and needs to do two main jobs. First, it keeps fluids within their required locations, and second, it holds compression within the cylinder. As soon as a head gasket breaks, you’ll experience the following issues.
- Lack of Power
- Overheating
- Rough Performance
- Trouble Starting Your Lawn Mower
- Trouble Keeping Your Lawn Mower Running
- Whooshing Sound
- Leaking Oil from the Head Gasket
- Oil Smoke from the Exhaust Pipe
- Oil & Air in the Coolant
- Oil & Coolant in the Cylinder Head
- Loss of Compression
How to Tell If Your Lawn Mower Engine is Blown (5 Symptoms)
If your lawn mower has an issue with the head gasket, you’ll experience several symptoms. Here are some signs you might run into if your lawn mower has a blown engine.
Lack of Power
The first thing you’ll probably notice if your head gasket is on its way out is a loss of power. The pressure created from the combustion process to move the piston can escape when the gasket has issues and reduces the engine’s power. Depending on where your head gasket is, the signs can be different.
Overheating
The next symptom you might experience is that your lawn mower will overheat. Your lawn mower overheats because it has to work much harder due to the lack of power. Also, if the gasket is blown between the oil passages and the coolant passage, both fluids will get contaminated, and won’t be able to perform as intended.
Rough Performance
Now, if you add a lack of power and overheating together, you end up with a lawn mower engine that runs rough. So, if your lawn mower is noticeably struggling, like with surging RPMs, you could be looking at a blown head gasket.
Trouble Starting Your Lawn Mower
Next on the list of symptoms is trouble starting your lawn mower. Usually, you would probably look at the usual suspects like a dirty carburetor, a dirty spark plug, or maybe an old fuel filter. But if all of these components look okay, knowing where else to look can be confusing. Well, the head gasket could be your issue.
I’m pretty sure that most of the lawn mowers you see sitting on the side of the road for trash collection have a blown head gasket. So, knowing what to look out for might keep your lawn mower out of the mower graveyard.
Trouble Keeping Your Lawn Mower Running
Last on my list of signs of a blown lawn mower engine is trouble keeping your lawn mower running. Stalling becomes a real problem once a head gasket starts to go bad and when it has totally blown. This can be down to a number of reasons depending on the design of your engine.
For example, you might have oil or coolant in the combustion chamber, making ignition difficult, overheating is definitely going to make your lawn mower stall, and finally, you might have a complete loss of compression preventing your mower from running.
Signs of a Blown Head Gasket (6 Signs)
Now that you have a good idea of the problems a blown gasket can cause, let’s go over how to tell if a lawn mower engine is blown. There are a bunch of different telltale signs that will confirm your head gasket is at fault. Here’s what to look out for and some tests you can run.
Whooshing Sound
If you have a lawn mower blown head gasket, then you might be able to hear where it is blown. If the gasket is blown from the cylinder to the outside of the head, then the pressure in the cylinder head will be able to escape.
So, you might hear a whooshing sound as air escapes while the pistons move up and down. Sometimes you can actually feel the air leaking if you place your hand close to the gasket. Be careful of the moving parts and the hot engine if you try this test.
Leaking Oil from the Head Gasket
Another pretty common sign is oil leaking from between the head and the engine block. This is where the engine compression pushes oil out of the blown gasket. So, inspect your lawn mower where the head meets the block and see if you have a noticeable leak.
Oil Smoke from the Exhaust Pipe
Inside your engine, there might be oil ports that allow oil to travel around the engine. So, if the gasket is blown between the cylinder port and one of the oil passages, then the oil might get into the combustion chamber. You’ll notice smokey exhaust if there is an internal break in the head gasket.
Oil & Air in the Coolant
If you have a water-cooled engine, like a John Deere tractor mower, then water runs through the engine to regulate the engine temperature. If the gasket is broken between these two parts of the engine, you’ll end up with air and oil in the water-cooling system.
A quick way to check is to look at the top of the water radiator or reservoir. If you find oil floating on top of the water, then your gasket is at fault. Another sign is seeing bubbles when checking the tops of the radiator or the water reservoir. Bubbles happen when the engine forces air from the cylinder head into the cooling system.
Oil & Coolant in the Cylinder Head
You also want to look inside the cylinder head when figuring out how to tell if the lawn mower engine is blown. The easiest way to check the cylinder head is to remove the spark plug and look inside the engine. If you find oil or coolant inside the head, you’re more than likely dealing with a break in the gasket.
Loss of Compression
If you have been through the lawn mower blown head gasket symptoms and discovered a few signs, then you can confirm this by conducting a compression test to see if the lawn mower’s head can hold a specific amount of air pressure without leaking. You can test the air pressure by removing the spark plug and connecting a pressure gauge. Then, start the engine by using the starter pull cord or the electric starter and test the pressure. If the pressure is below the desired reading or reduces over time, the cylinder head has a leak.
However, bad results could also signify problems like a worn-out cylinder or worn-out piston rings. This test only confirms a compression problem but doesn’t specifically single out the head gasket. So, you’ll need to do more investigating.
Inspecting a Lawn Mower Blown Head Gasket
By far, the best way to confirm you have a blown head gasket is to conduct a visual inspection. If you have been through all the lawn mower blown head gasket symptoms and done the tests, then the final step is to inspect the actual gasket.
Now, this is a pretty lengthy job because you have to strip down the lawn mower engine. With some lawn mowers, this is pretty straightforward, but more complex engines require more work. You’ll probably have to remove the exhaust pipe, carburetor, valve cover, push rods, cooling system, and the actual head to get to the lawn mower blown head gasket. But with some patience and a handful of tools, it’s not too difficult.
Is There Anything You Can Do in Either Case?
I know that stripping down an engine might sound like a lot of work. So is there anything you can do instead? Well, this all depends on how the head gasket is broken. If it’s damaged internally, say between the cylinder and one of the oil/coolant passages, then, unfortunately, you need to replace the gasket.
There are products you can flush through a water cooler mower engine to repair a leak, but I’ve never heard of anyone having much success, especially long-term.
Now, if the break is from the cylinder straight to the outside of the engine, then you might be able to do a temporary fix. You’ll find products that can seal a gasket from the outside to block the air from escaping. But again, this is only a temporary fix. My best advice is to grab a new gasket and carry out a long-term fix.
What Causes a Blown Head Gasket on a Lawn Mower?
General wear and tear is the main reason why head gaskets blow. But there are a few things you can avoid to ensure your gasket doesn’t break. Overheating is one of the main causes of a head gasket’s early failure.
So, make sure to use the right lawn mower oil type, keep your oil topped off, perform regular oil changes, and keep the cooling systems in tip-top shape, including cleaning the cooling fins on the top of the flywheel and the water-cooling system.
Leave a Reply