What are some potential causes for a Volvo VNL to keep purging air? There are several potential issues that can cause a Volvo VNL semi truck's air dryer to keep purging. These include: Faulty air dryer filter: The air dryer filter is responsible for removing moisture and contaminants from the compressed air as it passes through the purge system. If the filter is clogged or otherwise faulty, it may cause the purge system to initiate more frequently. Air leaks in the brake system: If there are air leaks in the brake system, it may cause the pressure in the air tanks to drop, which can trigger the purge system. Faulty air compressor: The air compressor is responsible for generating the compressed air used in the brake system. If the compressor is faulty or not functioning properly, it may cause the purge system to initiate more frequently. Faulty purge valve: The purge valve is responsible for allowing a small amount of air to flow through the air dryer filter during the purge cycle. If the purge valve is faulty or not functioning properly, it may cause the air dryer to initiate the purge more frequently or for longer periods of time than necessary. Faulty turbo cut-off valve: The turbo cut-off is located in the air dryer base as well, along with the purge valve and works in sync with the other valves, if any of the parts inside of the air dryer base are malfunctioning it can cause frequent purges. Faulty air dryer base: The air dryer base is responsible for supporting the air dryer, containing all of the valves, ports, sensors and tubing, connecting it to the brake system. If the base is faulty, clogged or not functioning properly, it may cause the air dryer to initiate the purge more frequently. Faulty or failed air compressor governor: The air compressor governor is responsible for controlling the output of the air compressor. If the governor is faulty or has failed, it may cause the air dryer to initiate the purge more frequently. Blocked or leaking air compressor signal line: The air compressor signal line is usually a small tube that connects the air compressor to the air dryer. If this line is blocked or leaking, it may cause the air dryer to initiate the purge more frequently. Blocked or leaking air compressor discharge hose: The air compressor discharge hose is responsible for carrying compressed air from the compressor to the air dryer. If this hose is blocked or leaking, it may cause the air dryer to initiate the purge more frequently. Air leaks in the suspension system: If there are air leaks in the suspension system, it may cause the pressure in the air tanks to drop, which can trigger the purge system. Air leaks in the transmission system (if applicable): If the Volvo VNL semi truck is equipped with an air-assisted transmission system, there may be air lines that run from the air tanks to the transmission. If these lines are leaking, it may cause the air dryer to initiate the purge more frequently.
Shop Talk
Volvo D13 Most Common Failing Points
1 comment
Overview The Volvo D13 Pre and Post DEF and other aftertreatment equipment both have their own issues. Below are a list of some in depth failing points and descriptions most shops may not take the time to tell you about. 1. Injector Sleeves aka Cups Leak This is arguably the most talked...
Semi Truck Air Dryer Filter Troubleshooting & Tips
One of the most obvious signs that your air dryer may be bad is if you notice a lot of water draining from the air tanks when you use the drain valves. This could be an indication that the air dryer filter needs to be replaced. In addition to the filter needing to be replaced due to moisture etc a failed filter can physically fall apart and clog the air system. Another issue to watch out for is oil in the air brake system. If your air compressor is failing, it may introduce oil into the system, which can clog the air dryer filter and cause problems with the brakes, suspension, transmission (if applicable) etc. If you notice oil in the system, it is important to troubleshoot the issue and possibly consider replacing the air compressor. Reduced air pressure: If you are experiencing reduced air pressure in your truck's air brake system, it could be a sign that the air dryer is faulty. Reduced air pressure can cause the brakes to feel "spongy" and can lead to longer stopping distances. Leaks: If you notice any leaks in the air dryer or its components, it could be a sign that the air dryer is faulty. Leaks can cause air pressure to drop and can lead to reduced braking efficiency. Excessive brake wear: If you are experiencing excessive brake wear, it could be a sign that the air dryer is faulty. A faulty air dryer can cause the brakes to be applied more frequently, leading to increased wear and tear on brake components.
How do you measure the brake shoes on a semi truck?
On the steering axle of a semi truck, the minimum required thickness for brake shoe lining is 4.8 mm (3/16 inch) at the shoe center for a shoe with a continuous strip of lining, 6.4 mm (1/4 inch) at the shoe center for a shoe with two pads, or worn to the wear indicator if the lining is so marked, for air drum brakes. For air disc brakes, the minimum required thickness is 3.2 mm (1/8 inch). On non-steering axles (also known as drive axles or tag / additional axles) of a semi truck, the minimum required thickness for brake shoe lining is 6.4 mm (1/4 inch) or to the wear indicator if the lining is so marked (measured at the shoe center for drum brakes). For disc brakes, the minimum required thickness is 3.2 mm (1/8 inch). If your measurement is less than the minimum required thickness, the brake shoe lining may need to be replaced.
