Making a hydraulic lifter adjustment requires the right tools and knowledge. Hydraulic lifters are designed to keep the valvetrain free of any clearance, leading to a quieter engine operation. This is done by adjusting the nut on the rocker arm which determines how much clearance is left between the valves and the lifter. Though it is possible to adjust the lifters on your own, it is often best to leave this task to a professional mechanic. If the adjustment is done incorrectly or too aggressively, there is a risk of damaging the engine. In some cases, hydraulic lifters may have to be replaced instead of adjusted so it’s important to understand which option is best for your vehicle.