Maintenance
Brake System Maintenance Check: Your Key to a Safer Fleet
As stated before, air brake safety is critical in the waste industry. With all the advances in the braking system, nothing can replace a good maintenance program that begins with the correct inspection procedures.
Len Gonzalez
In the waste industry, proper brake system maintenance is most critical. Waste vehicles use their brakes more often than any other vocational vehicle; therefore, proper maintenance and shop procedures provide a safe and dependable brake system that will save time and money. The importance of air brake safety cannot be overstated. Every fleet should adopt standards on how often their trucks are inspected (PM) and keep good records to support those inspections. Driver input via Driver Vehicle Inspection Reports (DVIR) will give feedback into any issues dealing with the brake system. Vehicle breakdowns and road calls are expensive and threaten good customer service for the waste fleet. This article is designed to help with your brake inspections to detect problems early and avoid service issues later.
Inside/Outside the Vehicle
When you inspect the brake system, walk around the outside and look underneath the vehicle. Check to make sure the brake chambers are straight and that all air hoses are tied properly. Inspect the air pressure in all tires; low air pressure can create excessive heat leading to premature brake component wear. In the cab, make sure the ABS light is not on, which would indicate an ABS problem should be corrected. Antilock Braking Systems are an important component on your truck and should be operational at all times.
Underneath the Vehicle
Chock the wheels and use proper lockout procedures as these inspections are performed. Always wear proper eye protection when conducting any work under a vehicle.
Overall Check
Visually check the entire air system, from the air tanks, air hoses, valves and brake chambers. All the brake chambers should be the same size and stroke (ie., standard or long stroke). If you are unsure what was specified on your truck, contact your local dealer. Next, look for excessive corrosion that may indicate an air leak and make sure air hoses are tied up properly without binding. A low-hanging air hose can be snagged at a landfill, or a hose rubbing along the frame may chafe and fail. Check that your ABS lines are in good condition and are not stretched. All hoses leading from the valves to the brake chambers should be the same size and length; air hoses of different lengths will cause imbalances in the brake system.
Brake Chambers
Now look at the mechanical parts of the brake system. Start with the brake chambers and inspect carefully. The brake chamber is the heart of the brake system; improper operation will affect the entire system. Visually check the chamber for corrosion, especially around the power spring (parking) side, the air hose fittings, and the mounting bolts. Check around the mounting bolts on the base of the chamber for cracks. If any of these issues are present, brake chamber replacement may be necessary. Also, see if the push rod is straight from the rear of the chamber and is not rubbing against the housing. Lastly, ensure the chamber’s weatherseal™ plug is in place.
Slack Adjusters
Inspect the slack adjusters for excessive wear, movement, corrosion and excessive grease. Use the proper grease recommended by your slack adjuster manufacturer. Some manufacturers require specific grease.
S-cam Bushings
Grasp the s-cam and if there’s play, the s-cam bushings may be worn and should be replaced. Worn s-cam bushings will greatly affect brake adjustment.
Shoes and Drums
Visually check the shoes for wear and oil contamination. If any oil is present, the shoes must be replaced. Examine the brake drum for discoloration and for cracks.
Brake Operation
The next portion of the inspection will require an assistant in the truck cab to operate the brakes. While the assistant releases the brakes, listen carefully. Note any air leaks around valves, hoses, and brake chambers. The standard rule for air systems is air loss cannot exceed 3 psi in 5 minutes. Follow the proper procedures for locating and repairing leaks. When dealing with air leaks at the valves, make sure you test the brake chamber to eliminate the possibility of pass-through from the chamber. If you replace any air hose, make sure it is the same length and size of the original or a brake imbalance will result.
Now have the assistant apply the brakes slowly and witness the operation of all wheel ends. The stroke should be straight without binding and the chambers should not excessively flex once the shoe contacts the brake drum. Flexing will be an indication of a cracked mounting bracket that will need replacing. Make sure there are no air leaks from the brake chamber during the operation. If you witness the overstroke indicator on the push rod when the chamber has reached the end of its travel, you have a brake overstroke issue that must be inspected further to determine the cause and repair. This would include testing the slack adjuster, checking the s-cam bushings or further inspection of the foundation brake. A brake adjustment made only to remedy this condition will only temporarily solve the problem but will not assure a secure braking system.
Brake Stroke
Next check brake stroke free play. Free play is defined by the time the push rod from the chamber moves forward to the time the slack adjuster moves the s-cam. Free play should not exceed ¼”. Excessive free play is often caused by a worn clevis-pin.
Now check the brake stroke.Accurate brake stroke is critical for the proper operation of the brake system. Brake stroke (also known as brake adjustment) is checked by physically measuring the brake rod travel when the brakes are applied. A tape measure must be placed at the bottom of the brake chamber, and with the help of the assistant, the brake pedal is depressed and the travel is checked. Brake stroke measurement varies between chamber sizes (see Figure 1, page xx).
Record brake stroke measurements for all wheels and keep them with the preventive maintenance records for the truck. This will allow for helpful reference when diagnosing a brake problem that may arise in the future.
A Good Start
This is only an abridged version of a brake inspection. Your fleet may have varying requirements and procedures to follow in addition to the ones discussed here. The frequency of the inspections must be determined by the fleet based on the use of the vehicle, environmental and weather conditions, age of the vehicle and other fleet-specific factors.
As stated before, air brake safety is critical in the waste industry. With all the advances in the braking system, nothing can replace a good maintenance program that begins with the correct inspection procedures. This can provide early detection of faulty equipment that increases driver confidence, lowers breakdown/road call rates and puts a safer vehicle on the road.
Len Gonzalez is Southeast Regional Sales Manager for MGM Brakes (Charlotte, NC)focusing on the waste industry. He has worked in the heavy-duty vehicle business for more than 30 years after being exposed to trucks at an early age at his family’s truck repair business in West Tampa, FL. Since than time, Len has been involved in vehicle maintenance management, procurement, vehicle and parts specification, fleet management, leasing, logistics sales and equipment use for companies such as Southern Wine and Spirits, Ryder and Penske. Len can be reached at (813) 476-1534 or email [email protected].