What 393.47(f) means in plain language
When you receive a citation for 393.47(f), the inspector has determined that one or more of your brake actuators, chambers, or related brake components are not functioning as they should. Brake actuators and chambers are the mechanical or pneumatic devices that convert brake pressure—either from your foot pedal or air system—into the physical force that stops your wheels.
This citation applies when these components show visible damage, leakage, rust, corrosion, or functional failure that would prevent them from working correctly. Unlike some brake violations, this code focuses specifically on the condition of the actuator and chamber hardware itself, not on slack adjusters or overall brake performance metrics.
The regulation requires these components to be in good working order. If an inspector finds evidence that they are defective or not functioning properly, the violation is documented. This is a maintenance and condition issue—it means something about the hardware itself needs attention.
What our enforcement data actually shows
Across our 13 million+ inspection records, 393.47(f) has generated 351 all-time citations. Over the last 12 months and last 90 days, we recorded zero citations for this code, indicating it is not currently being cited in our dataset.
Critically, our data shows an out-of-service rate of 0.0%—all 351 citations on record resulted in the vehicle remaining in-service. This stands in sharp contrast to the all-FMCSR average out-of-service rate of 31.4%. In other words, inspectors have consistently cited this violation without placing the vehicle out of service, suggesting the defect was either correctable on-site or did not rise to the level of immediate safety risk that triggers an OOS order.
393.47(f) ranks #1033 out of 3,036 FMCSR codes by total citation volume. While not among the most frequently cited violations, it remains part of the enforcement landscape for brake-related vehicle maintenance.
Who gets cited most
Our inspection records do not include geographic state-level breakdowns in this dataset, so we cannot identify which states issue the most 393.47(f) citations. However, we can see the carriers most frequently cited for this violation.
Servicio Internacional de Enlace Terrestre SA de CV (USDOT 818175) leads with 6 citations, followed by Route 281 Logistics LLC (USDOT 3139107) and Leon Jessop LLC (USDOT 4044888), each with 4 citations. Several other carriers—including Santos Gonzales, Transportes Especializados Antonio Garza Ruiz SA de CV, CG Hunt, Alee's Transport LLC, Sandra Patricia Casanova Guillen, KI Trucking Company LLC, and Hairpin Trucking LLC—appear with 3 citations each in our records. The data shows these fleets with documented violations of brake actuator and chamber condition, but citation volume alone does not indicate systematic negligence; maintenance defects can occur across any carrier depending on vehicle age, inspection frequency, and environmental factors.
Top vehicle makes cited for 393.47(f) include Freightliner (43 citations), Freightliner again listed separately (36 citations), Kenworth (22 citations), Volvo (20 citations), KW-badged units (18 citations), and Utility trailers (18 citations). Peterbilt, other makes (OTHR), Utility again, and Great Dane round out the list. The concentration of citations on heavy-duty Class 8 tractors and trailers suggests this violation is most often encountered on long-haul and regional equipment.
How severe is this compared to similar codes
Within the Vehicle Maintenance category, 393.47(f) sits among several closely related violations. To put its enforcement frequency in perspective:
393.47E — Slack adjuster defective has 180,363 all-time citations with a 0.0% out-of-service rate, making it far more prevalent than 393.47(f)'s 351 citations. Both codes share a 0.0% OOS rate, meaning neither typically results in immediate out-of-service action.
393.9(a) — Inoperable required lamps shows 660,737 citations with a 15.4% OOS rate, indicating lamp violations are enforced at roughly 2,000 times the frequency of brake actuator defects, though still with lower OOS rates than the all-FMCSR average.
396.3(a)(1) — Inspection/repair/maintenance (general) has 236,919 citations and a 45.3% OOS rate, well above the all-FMCSR average. This broader maintenance code is cited more often and results in out-of-service placement significantly more frequently than 393.47(f).
The 0.0% OOS rate for 393.47(f) is notably different from the typical enforcement pattern. It suggests that while inspectors document the defect, they have not determined it warrants immediate removal from service in any of the 351 cases recorded.
How to avoid it
Prevent a 393.47(f) citation by making brake actuators and chambers part of your regular pre-trip and post-trip inspection routine:
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Inspect brake chambers visually before each trip. Look for cracks, leakage (oil or air), rust, corrosion, or visible damage to the metal housing. Pay special attention to units on Freightliner, Kenworth, and Volvo equipment, which account for a large share of citations in our database.
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Feel and listen for brake responsiveness. During your walk-around and before pulling onto the road, perform a service brake test. Apply the brakes firmly and listen for any unusual sounds, feel for soft or spongy pedal response, or notice if the truck pulls to one side. These can indicate actuator or chamber problems.
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Check for leaks in your air and hydraulic brake systems. Air leaks around chambers or actuators, or fluid pooling beneath brake components, are red flags. A slow leak today becomes a defective component tomorrow.
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Schedule maintenance at the first sign of brake softness. If you notice the brake pedal feels different, requires more pressure than usual, or the truck is slower to stop, report it to your fleet maintenance team immediately. Don't wait for an inspection to catch it.
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Know your truck's brake type. Whether your vehicle uses air-over-hydraulic or full pneumatic brakes, understand how your specific chambers and actuators are supposed to function and what normal operation feels and sounds like.
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Document your pre-trips. Record what you inspect and when. If you catch a potential defect early and report it, you demonstrate due diligence if an inspector later finds an issue.
Brake safety is non-negotiable. A citation for defective actuators or chambers is the inspector's way of saying they found hardware that isn't working as designed. Address it promptly, and you'll reduce your risk of future citations and, more importantly, keep yourself and others safe on the road.