How to Use a Semi Truck Jake Brake

The Jacobs Engine Brake (sometimes known as a Jake Brake) is used mainly in large vehicles with diesel engines. The Jake Brake uses the high compression of the diesel engine to slow the vehicle without using the service brakes. The repeated use of the regular service brakes in large vehicles will cause the brakes to overheat and possibly fail. Although not a substitute for regular service brakes, the Jake Brake can help keep your vehicle under control and lower service brake maintenance costs.

Instructions

1. Familiarize yourself with the dashboard controls. Locate the Jake Brake ON/OFF switch and the LOW/HIGH or LOW/MEDIUM/HIGH switch.

2. Allow the engine oil to reach full operating temperature. Switch the Jake Brake to the ON position and use LOW range. Lift off the throttle to automatically slow the vehicle. Switch the range to MED or HIGH if in dry, level conditions you are still using your service brake.

3. Switch the range to HIGH in dry conditions when descending a grade for maximum braking.

4. Shift to a higher gear if the Jake Brake is holding the vehicle at too slow a speed when descending grades. Shift to a lower gear if the vehicle is descending the grade too rapidly. Use the service brakes if needed when shifting to prevent the engine from over-speeding. Find the right gear to allow the Jake Brake to hold the vehicle at the desired speed without having to use the throttle or service brakes.

5. Turn the Jake Brake off if road conditions are wet or slippery. Insure that your vehicle is holding traction by using the engine's natural holding power. Make sure that there is plenty of distance between your vehicle and others. Turn the Jake Brake back on and use LOW range. If the vehicle is holding traction, leave the Jake Brake on. Avoid using MED or HIGH range in slippery conditions. Turn the Jake Brake off if the vehicle starts to lose traction.

Tips & Warnings

• The Jake Brake is not a substitute for service brakes. Apply service brakes when coming to a complete stop.

• Do not use the Jake Brake on slippery surfaces until you have mastered it on dry pavement. Using the Jake Brake on a slippery surface can cause the vehicle to slide out of control.

• Never use the Jake Brake if the vehicle is empty or when bob tailing (driving a semi tractor without a trailer).

References

• Jake Brake Operators Manual