If you live in any of the northern states or Canada, you have probably owned or ridden a snowmobile at some point. Snow and wide-open spaces, fresh air, and sunshine. Ah, the carefree life of a winter sports enthusiast. But what if you have a problem and your sled overheats?
Can a snowmobile run without a thermostat? The good news is that you can remove the thermostat and not blow up your sled. Ultimately you can ride without a thermostat but it’s a little more complicated than that.
Before we dive into the details about running your snowmobile without a thermostat, let's take a look at just how the cooling system works and what the purpose of having a thermostat is in the first place.
The Purpose Of A Thermostat
Most people assume that the thermostat controls the temperature of the coolant. That is only partially correct. While the thermostat is temperature-controlled, it is there to direct the flow of coolant within the system.
A thermostat is a spring-operated, temperature-regulated switch. When an engine is started, the switch is closed, keeping coolant circulating in the engine until it reaches operating temperature.
When the coolant reaches a high enough temperature to open the thermostat, coolant is routed through the part of the system that helps cool it. In a car, that is the radiator, while most snowmobiles employ a heat exchanger.
This video, while made to explain a car engine, gives an excellent description of how the process works. The video also shows how to test a thermostat to make sure it is functioning correctly and the principles are the same on a snowmobile so it is very relatable.
How Does A Snowmobile Cooling System Works
The most common cooling system in snowmobiles uses a heat exchanger.
Coolant flows through the engine, heating as the engine warms up. Once operating temperature is reached, the thermostat opens and routes the hot coolant to the heat exchanger. Heat is dissipated by snow thrown from the fins across the heat exchanger. The cooled liquid then continues the flow through the engine to cool the engine.
Some snowmobiles use a fan, or forced air, system for cooling. These are usually small engine sizes because they tend to run cooler. Fans may also be used in addition to a liquid-cooling system. When a snowmobile isn’t moving, it isn’t cooling. The recommended engine warm-up time is about five minutes to allow the engine to reach operating temperature. If you let it sit idling for longer, you risk overheating.
The type of riding you do on your sled will impact the engine heat. Operating in low-snow conditions will cause an engine to run hot because the snow is needed to cool the heat exchanger.
If you want to learn the basic of a snowmobiles cooling system then you should definitely check out this next video. It describes the process in an easy to understand fashion.
What Are The Two Snowmobile Engine Types
There are two basic engine types used on snowmobiles: 2-stroke and 4-stroke. Although they are very similar, there are minor differences in the way they convert fuel (gasoline) to kinetic energy (motion).
The 4-stroke engine was invented by Nikolaus Otto in 1867. The four strokes are:
Fuel is brought into the cylinder head during the intake stroke as the piston moves down. The piston then moves back up, compressing the vapor. A spark is generated, which causes an explosion (combustion) in the cylinder. The pressure of the explosion moves the piston back down. The exhaust leaves the piston at the bottom of the stroke.
Pistons are attached to a crankshaft by arms, or connecting rods, which force a rotation within the engine. This rotation is what allows the engine to transfer the energy from the pistons to the drive mechanism to create movement.
One of the biggest advantages of a 4-stroke snowmobile is that it uses regular gasoline, as opposed to a gas and oil mixture. This creates a cleaner burn, fewer fumes, and easier maintenance.
Some snowmobiles use a 2-stroke engine.
The most significant difference between 4-stroke and 2-stroke engines is the way they are configured. The compression stroke draws in fuel and compresses it simultaneously. The combustion stroke creates a spark (to cause the explosion) and expels exhaust simultaneously.
There are several advantages with a 2-stroke engine:
- No valves, which reduces weight
- The engine fires on every revolution (4-stroke engines fire every other rotation)
- More power
- Can operate in any orientation (even upside-down)
These advantages make 2-stroke engines lighter, easier to manufacture, and less expensive. They can produce twice the amount of power as a 4-stroke engine.
The major disadvantage of a 2-stroke engine is that it requires a fuel/oil mixture rather than plain gasoline. The oil is needed to lubricate the crankshaft, cylinder walls, and connecting rods. This adds an extra expense because the oil burns off while in a 4-stroke system, it is reused.
Because of the fuel/oil mix, a 2-stroke will generate more exhaust fumes, although overall, they do burn cleaner than a sled with a 4-stroke engine.
Check out this video that explains the major differences between a 2-stroke and 4-stroke engine very well.
Can A Snowmobile Run Without a Thermostat?
The general consensus on liquid-cooled snowmobiles is that they can be operated without a thermostat under most conditions. Snowmobile manufacturers and most mechanics will not recommend it, though. From a mechanic’s viewpoint – if your sled was made with a thermostat, you should keep it.
The thermostat controls the flow of coolant through the engine, allowing it to flow slowly through the heat exchanger. This aids in heat transfer, cooling the liquid before it returns to the engine. With no thermostat, the fluid flows too quickly through the heat exchangers and doesn’t cool as efficiently.
Many riders think that running your sled without the thermostat means that your sled will run cooler. This might be good if you frequently run in low snow conditions. It should be noted that running the snowmobile for an extended time will still cause it to run hot.
There are many questions to ask yourself before deciding to remove your thermostat. Are you familiar enough with your sled to “feel” when it is getting too hot? Do you know the terrain you will be sledding in? Will removing the thermostat void any warranties or service plans on your sled?
Once you have weighed all the pros and cons, you can determine whether you are comfortable running your sled without a thermostat.
What Could Be Causing Overheating If Not A Thermostat Fail?
If your snowmobile is overheating, it might not be the thermostat at all. There are a few minor issues that might be causing it to overheat.
Low Or Incorrect Oil
The first thing you need to check is your oil. Make sure you are running the correct oil in your engine. With a 4-stroke engine, the oil should be changed periodically based on your manufacturer’s specifications. In a 2-stroke engine, oil is mixed with the fuel and should be added every time you fill the tank.
Wrong Fuel Type
Check your fuel. Most snowmobiles call for higher-grade 91-octane fuel without ethanol. If you are pulling out your sled for the first time and didn’t drain the fuel prior to storage, it is recommended to drain and fill it with fresh fuel for the new riding season. If you plan to use a fuel stabilizer, check with your sled manufacturer or owner’s manual for recommendations.
The coolant level is an important check and should be performed before every ride. Check the system for leaks, top off the level if needed, and make sure that all hoses are connected properly.
Check the wiring to heat sensors to make sure they are in good condition.
A general engine check should be on your list also. An incorrect fuel/air mixture, poor compression, or spark problem could make the engine work too hard. This may cause it to overheat, perform less than optimal, or just stop running altogether.
Have a Safe and Enjoyable Snowmobile Season
You don’t have to be a mechanic to perform pre-ride checks on your sled. Proper preventative maintenance will help your snowmobile last longer. Get in the habit of checking out your sled.
Keeping your sled in tip-top condition will assure that you have a safe and enjoyable riding season.
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My Favorite Gear
Gloves – Carhartt WP Gloves
Boots – Fly Racing Marker Boots
Jacket – Fly Racing Aurora Snowmobile Jacket