Electric Cars

Maintaining the braking system of a fifth-generation Ram 2500 is crucial due to its robust design and common usage in hauling heavy loads. A successful brake overhaul demands a comprehensive examination of the entire system and the selection of components that meet the vehicle's rigorous thermal and mechanical specifications. This guide focuses on the 2019 and newer Ram 2500 models, highlighting their distinct heavy-duty components and specialized service techniques, differentiating them from the lighter-duty Ram 1500.

The braking mechanism in the Ram 2500 incorporates four-wheel vented disc brakes, complemented by dual-piston sliding calipers. An independent parking brake system, utilizing shoes that engage with a drum surface within each rear rotor's hub, is also present. The brake booster's setup varies based on the engine type. Models equipped with the 6.4L Hemi engine feature a dual-diaphragm vacuum booster, which is assisted by an electric vacuum pump situated on the engine's front left side. This pump's operation is dictated by the Powertrain Control Module (PCM) in response to dynamic driving conditions. Conversely, the 6.7L diesel engine variants employ a Hydro-Boost system, powered by the vehicle's power-steering pump, offering a limited backup assist via an accumulator if primary pump pressure is lost.

Before any dismantling, a preliminary road test is recommended to assess pedal feel, assistance, any pulling sensation, vibrations, or unusual noises during normal braking. This helps in pinpointing the actual source of any complaints; for example, a vibration attributed to the front brakes might actually originate from the rear, or an assist issue could stem from the vacuum or power-steering system rather than the foundational brakes. It's essential to clean the master cylinder cap area and confirm the fluid level is at its maximum. For diesel models, a check of the power-steering fluid level, hoses, and lines is also necessary, as the Hydro-Boost system relies on this circuit. Insufficient fluid, leaks, blockages, or a weak pump can all lead to reduced braking assistance. For gasoline engines, the vacuum lines for the booster and the electric pump's functionality should be checked.

Inspect the wear patterns of both inner and outer brake pads on each side of every axle. Discrepancies in wear can indicate issues such as stuck hardware, binding pads, piston malfunctions, or slide problems. Pads should be replaced across an entire axle if the thinnest part of the lining measures 1 mm (0.04 inch) or less. Further inspection should cover boots, pistons, slides, hoses, and bleeders for any signs of damage, leaks, or corrosion. Rotor dimensions are critical; the minimum thickness for front rotors is 37.4 mm (1.47 inches) and 32.4 mm (1.28 inches) for the rear. The maximum allowable runout is 0.020 mm (0.0008 inch), and the maximum variation in thickness for a loose rotor is 0.008 mm (0.00031 inch). The internal surface of the parking brake also requires attention, with a maximum drum diameter of 207.2 mm (8.157 inches).

During front brake maintenance, ensure the caliper and adapter are properly supported to prevent strain on the brake hose. Thoroughly clean the pad contact points and the hub surface without removing any underlying metal. Install new anti-rattle clips, confirm unhindered pad movement, and verify that both pistons retract smoothly. Since the rotor mounts over the hub studs, the cleanliness of the hub and consistent torque application for wheel fasteners are vital for managing installed runout. For the rear brakes, the parking brake assembly requires additional attention. If a rotor cannot be easily removed, it might be caught on the parking brake shoes; releasing the pedal and adjusting the star wheel can resolve this. Once the rotor is off, examine the shoes, springs, adjuster, cable operation, and the drum surface. Clean the hub and bracket, check piston and slide mobility, and install new hardware and sealing washers as needed. Always replace caliper hardware, as old clips can impede pad movement and lead to uneven wear.

When bleeding the hydraulic brakes, use fresh fluid compliant with SAE J1703-F and DOT 3 standards. The recommended bleeding sequence is: right rear, left rear, right front, and then left front, ensuring the reservoir remains full throughout the process. For pressure bleeding, utilize the appropriate adapter, typically at 15-20 PSI, depending on the equipment's limitations. If air has entered the Hydraulic Control Unit (HCU), perform an initial bleed, then use a compatible scan tool to run the ABS Miscellaneous menu's HCU bleed routine, followed by another base system bleed. Afterward, set the fluid to the correct level and confirm a firm pedal feel. The Hydro-Boost system typically self-bleeds. To bleed it, fill the power-steering reservoir, disable the engine, and crank it for a few seconds before rechecking the fluid level. Re-enable and start the engine, turn the steering wheel slowly from lock to lock twice, then shut off the engine and release accumulator pressure by pressing the brake pedal five times. Restart the engine, repeat the two slow lock-to-lock cycles, shut down, and adjust the fluid level. If the fluid appears foamy, allow the foam to dissipate before repeating the final steps.

Before adjusting cable tension, the parking brake shoes must be set. With the pedal fully disengaged and the front cable loosened at the frame-rail adjuster, rotate each star wheel via the backing plate hole until a slight drag is perceptible, then back it off until the drag ceases. Ensure both sides are adjusted symmetrically. Cable tensioner adjustment is typically only necessary after replacement or disconnection. After confirming cable movement and shoe adjustment, fully engage the parking brake pedal. Mark the non-threaded tensioner rod 1/4 inch from the tensioner's edge and tighten the nut until the mark is no longer visible. Release the pedal, verify both wheels rotate freely, confirm the brake holds, and then conduct a road test of the vehicle.