Brakes are the system a DOT inspector looks at hardest and the system that matters most when a loaded truck needs to stop. RDI Power repairs both air and hydraulic brake systems at our Brooksville shop, from Super Duty pickups towing campers to tractors, buses and diesel pusher RVs.
Air brakes
Air system components
An engine-driven compressor fills the tanks, a governor sets cut-in and cut-out pressure, and an air dryer removes moisture before it reaches the valves. From there, air goes to brake chambers that push S-cams through slack adjusters to spread the shoes against drums, or to air disc brakes. Spring brakes apply automatically if air pressure drops. ABS, low-air warnings, gauges, tank drains and the trailer gladhands and lines complete the system.
Air brake trouble signs
- Air leaks you can hear with the brakes released or applied
- Slow build-up, or pressure dropping overnight
- An air dryer purging constantly, or water in the tanks
- Pulling left or right, or uneven lining wear
- An ABS lamp on the tractor or trailer
How we check air brakes
We run leak-down tests released and applied, verify governor settings and build-up time, and check the air dryer and tank drains. At each wheel we measure pushrod stroke, inspect linings, drums and S-cam bushings, and confirm automatic slack adjusters are doing their job. An automatic slack adjuster that keeps going out of adjustment is a symptom; we look at the foundation brake behind it.
Hydraulic brakes
Hydraulic system components
Pads and rotors (or shoes and drums on older trucks), calipers, wheel cylinders, hoses, lines, the master cylinder, ABS and a power assist. Because diesels make little intake vacuum, the assist comes from a vacuum pump or a hydraulic booster powered by the steering pump.
Hydraulic brake trouble signs
- Squealing or grinding, or a pulsing pedal
- A soft, sinking or hard pedal
- Pulling under braking, or a wheel that runs hot
- Brake fade when towing downhill or in heavy traffic
How we check hydraulic brakes
We measure pad and rotor thickness, check rotor runout and caliper slide movement, test brake fluid condition and verify the power assist. Fluid absorbs moisture over time and boils sooner under hard use, which shows up as fade.
Brake repair work
For air systems: compressors, governors, dryers and cartridges, valves, chambers, slack adjusters, drums, shoes, S-cams and bushings, hoses and ABS sensors. For hydraulic systems: pads, rotors, calipers, hoses, master cylinders, boosters and fluid flushes. Worn brakes found late usually take rotors, drums or calipers with them; caught early, they are a lining job.
Brakes and inspections
Brake findings are a large share of what puts trucks out of service at roadside inspections. Our DOT inspections cover the full brake system, and our trailer repair work handles trailer brakes, lines and ABS. For more on heavy truck brakes, read semi truck brake repair.
If you hear a leak or feel a change in the pedal, bring the vehicle in before the next long haul.