What Is a Jake Brake and How Does it Work?

A Jake Brake is a type of compression release brake that helps truck drivers slow down their truck without wearing out the service brakes. Commonly called an engine brake, Jake Brakes are often used in large diesel engines on semi-trucks.


Using Jake Brakes when going downhill or when driving on freeway off-ramps can add years to the brakes and tires when used correctly. However, they result in a loud noise, so using them is prohibited in some areas.


Jake Brakes got their name from Jacobs Vehicle System inc., the company that created them. This type of brake is technically called a compression release engine brake, but it has many different names, including Jacobs Brake, Jake Nett Brake, Jake, and engine brake.

How Does a Jake Brake Work?

Truck drivers enable the Jake Brake by flipping an engine brake switch. Then all the driver needs to do to use the Jake Brake is take the pressure off the accelerator. The engine brake is deactivated when the driver uses the accelerator or clutch.


As a big rig is working, the air is forced into the engine cylinders as it enters the intake valve. This causes the air to compress which converts it into energy that can be distributed. Usually, the pistons take that energy and guide it to the rest of the vehicle to produce power. However, when a Jake Brake is activated, that air is pushed out the exhaust valves instead of being used to power the crankshaft and down-stroke. This results in a drag on the crankshaft, slowing the vehicle without any extra friction on the service brakes.


Because of how a Jake Brake works, drivers should avoid using them when on slippery road surfaces. The Jake Brake only affects the drive tires which increases the chances of causing a skid or jackknife. If the driver needs to use an engine brake to slow down on icy or snowy roads, the tractor needs to be lined up straight first or the truck might jackknife.

Are Jake Brakes Illegal?

You may have noticed signs that read “Engine brakes prohibited” or “Trucks please no Jake Brake”. This is because Jake Brakes make a very loud noise when the compressed air is pushed out the exhaust.


Because of the loud noise, several cities and towns have laws in place to prohibit the use of Jake Brakes. Engine braking is mostly regulated in residential areas that are close to interstates. The penalties for using a Jake Brake in a prohibited area depends on the city, but penalties can result in a fine of up to $500 or up to three months in jail. There are some exceptions to the bans on Jake Brakes if the driver needs to use them in an emergency situation.

Do Jake Brakes Hurt the Engine?

When used correctly, Jake Brakes don’t cause harm to the engine. Before beginning your trip, drivers should make sure their oil isn’t low. If an engine brake is used when oil is low, it can cause damage to the engine. Truck drivers should also be sure to let the engine warm-up before using an engine brake. If they use a Jake Brake with a cold engine, it can cause damage. In addition, it’s important that drivers don’t allow the weight of the truck going downhill to push the RPMs over the engine’s maximum RPM limit.


Jake Brakes that are used properly will extend the life of the service brake shoes and cause no harm to the engine.

Do Jake Brakes Use More Fuel?

The question of if Jake Brakes use more fuel is debated by many truck drivers. Despite the disagreeing positions, the general consensus is that the amount of fuel that might be wasted is worth it to avoid wear on the brakes.


Drivers who are looking to conserve fuel should avoid stopping unnecessarily, either with their Jake Brake or service brakes. Unnecessary stops interrupt the forward momentum of the truck and more fuel is needed to get the truck moving again. Coasting into red lights and stop signs is another easy way to conserve fuel.


Now that you know what a Jake Brake is, you can use them effectively to slow your truck and preserve your service brakes. Engine brakes are a valuable tool for truck drivers when used correctly and in the right areas.

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