Air Brake System Maintenance and Air Dryer Cartridge Replacement for NEWMAR DUTCH STAR
This comprehensive guide will walk you through repairing air brake system maintenance and air dryer cartridge replacement on your NEWMAR DUTCH STAR. Follow each step carefully and gather all required parts before beginning.
Required Parts
- Air dryer cartridge/desiccant – Part Number: Bendix 065225 or equivalent, Alternative: Meritor R955300, Price Range: $45-$85
- Air brake antifreeze – Part Number: CRC Sta-Lube Air Brake Antifreeze, Quantity: 1 pint, Price Range: $12-$18
- Air line fittings (if damaged) – Part Number: DOT-approved brass push-to-connect fittings, Sizes: 1/4″, 3/8″, 1/2″ as needed
- Brake chamber diaphragm kit (if needed) – Part Number: MGM 30/30 or 24/24 (size varies by axle), Price Range: $35-$75 each
- Slack adjuster (if manual adjustment needed) – Part Number: Haldex automatic slack adjuster, Price Range: $60-$120
- Air pressure gauge (for testing)
- DOT-approved thread sealant – Part Number: Permatex 56521
- Rubber mallet
- Wrenches (combination set metric and SAE)
- Air tank drain valve replacement (if needed) – Part Number: Bendix 065601
Step-by-Step Instructions
Step 1: Understanding Your Air Brake System
The Newmar Dutch Star, like most Class A diesel pushers, utilizes a sophisticated air brake system that provides superior stopping power for the vehicle’s substantial weight (typically 35,000-45,000 pounds GVWR). This system differs fundamentally from automotive hydraulic brakes and requires specialized knowledge for proper maintenance. The air brake system consists of several critical components: an engine-driven air compressor that generates compressed air, air storage tanks (typically primary and secondary tanks) that hold air at 90-135 PSI, an air dryer that removes moisture and contaminants from the compressed air, brake chambers at each wheel that convert air pressure into mechanical force, slack adjusters that maintain proper brake shoe clearance, and a complex network of valves and lines that control air distribution. Understanding this system is crucial because improper maintenance can lead to brake failure, which is obviously catastrophic. Most states require a special air brake endorsement on your driver’s license to operate these vehicles, reflecting the importance of understanding the system.
Step 2: Pre-Service Safety Checks and System Testing
Before you start any air brake maintenance, you must perform comprehensive system tests to establish baseline performance and identify specific problems. Park the motorhome on level ground, set the parking brake (which is spring-applied on air brake systems), and chock all wheels with heavy-duty wheel chocks rated for the vehicle’s weight. Start the engine and allow the air system to build to maximum pressure, which should be between 115-135 PSI depending on governor settings – this typically takes 2-4 minutes from a completely depleted state. Monitor both the primary and secondary air pressure gauges (all Class A motorhomes have dual air systems for redundancy) to ensure they build pressure simultaneously and equally. With the engine idling, release the parking brake and apply full foot brake pressure while observing the pressure gauges – pressure should not drop more than 3-4 PSI in one minute, indicating acceptable system leakage. Turn off the engine and continue holding the brake pedal for an additional minute – pressure loss should not exceed 2-3 PSI. If you hear any audible air leaks (hissing sounds), use soapy water to identify leak locations before proceeding with service.
Step 3: Air Dryer Cartridge Access and Removal
The air dryer on the Newmar Dutch Star is typically mounted on or near the chassis frame, usually in the engine compartment area or along the driver’s side frame rail. This cylindrical component is about the size of a large coffee can and is easy to identify by the air lines connected to it and the purge valve at the bottom. Before servicing, the air system must be completely depressurized to prevent injury from sudden air release. To depressurize, turn off the engine, release the parking brake (which will cause air to exhaust), and repeatedly pump the brake pedal until both air pressure gauges read zero PSI – this may require 20-30 brake applications. Locate the air dryer cartridge housing – it’s typically secured by a large threaded ring or several bolts around the perimeter. Using the appropriate wrench (often a large adjustable wrench or specialized spanner wrench), loosen the retaining ring by turning counterclockwise. Be prepared for some residual air and moisture to escape when you break the seal. Once the retaining ring is removed, the old cartridge should slide out of the housing – you might need to rock it gently or tap the housing with a rubber mallet if the cartridge is stuck.
Step 4: Cartridge Inspection and Housing Cleaning
With the old air dryer cartridge removed, this is your opportunity to thoroughly inspect the entire air dryer system for problems. Examine the old cartridge carefully – a healthy cartridge will be relatively dry with purple or blue desiccant beads visible. If the desiccant is saturated and appears pink or white, the cartridge was overdue for replacement. If there’s excessive oil contamination (black, oily residue), this indicates a problem with the air compressor allowing oil to pass into the air system, which is a serious issue requiring professional attention. Inspect the interior of the air dryer housing using a flashlight, looking for corrosion, cracks, or damage to the o-ring seating surfaces. Use compressed air (from a shop compressor, not the vehicle’s system) to blow out any debris or moisture from the housing. Clean the o-ring grooves with a lint-free cloth, being careful not to scratch the sealing surfaces. Check the purge valve at the bottom of the air dryer – this valve should operate automatically to expel moisture. Manually activate it by pulling the cable or pressing the valve to ensure it moves freely and fully closes.
Step 5: New Cartridge Installation
Unpack your new air dryer cartridge and inspect it for shipping damage. Verify that all o-rings and seals are properly positioned on the cartridge – these are usually pre-installed and should not be removed. Apply a light coat of clean air brake-approved grease or the lubricant provided with the cartridge to all o-ring surfaces. Carefully insert the new cartridge into the air dryer housing, ensuring it slides in straight without cocking or binding. The cartridge should seat fully with minimal resistance – if you encounter significant resistance, remove the cartridge and check for obstructions or misaligned o-rings. Once seated, thread the retaining ring onto the housing by hand, turning clockwise. Tighten the retaining ring to the manufacturer’s specified torque (typically 20-30 ft-lbs), or if torque specifications are unavailable, tighten hand-firm plus one-quarter turn with a wrench. Do not overtighten as this can crack the housing or damage threads. Reconnect any air lines that were disconnected, ensuring all fittings are secure and properly seated.
Step 6: System Recharging and Testing
With the new air dryer cartridge installed, you’re ready to recharge and test the air brake system. Start the engine and monitor the air pressure gauges as the system builds pressure. During initial pressurization, you should hear the air dryer purge valve activate several times as it expels moisture from the initial air charge – this is normal and expected. The system should build from 0 to 90 PSI within three minutes at idle speed; if it takes longer, there may be a compressor problem or significant leak. Once pressure reaches cutout (typically 125-135 PSI), the compressor should stop pumping and go into an unloaded state. Let the system sit with the engine running for 2-3 minutes, then perform the leakage tests described in Step 2. Apply the foot brake firmly while the engine is running and listen for the air dryer purge valve to activate – it should purge periodically during braking as system pressure fluctuates. Check all connections you serviced for leaks using soapy water solution, looking for bubbles that indicate escaping air.
Step 7: Post-Installation Break-In and Ongoing Maintenance
New air dryer cartridges require a brief break-in period to achieve optimal performance. During the first 100 miles of driving, the desiccant material needs to condition and adapt to the system. You may notice more frequent purging from the air dryer during this period – this is normal as the fresh desiccant absorbs accumulated moisture from the air tanks. After the first trip, manually drain all air tanks by opening the drain valves at the bottom of each tank – these are typically accessed from underneath the motorhome or from inside wheel wells. Hold each valve open until only air (no moisture) is expelled. This prevents water accumulation that can overwhelm the new dryer cartridge. Going forward, establish a maintenance schedule: manually drain air tanks monthly during active use season, inspect the air dryer cartridge annually, replace the cartridge every 2-3 years or whenever you notice excessive moisture in the air tanks, and immediately address any air leaks or unusual noises from the brake system. If you notice the low air pressure warning activating frequently, the parking brake auto-applying during normal driving, or unusual brake pedal feel, have the system professionally inspected immediately as these indicate serious problems.