W22 Brake Caliper Overheating
We own a 2004 National RV Dolphin on a W22 Workhorse chassis manufactured in December 2003. It is among those included in an Office of Defects Investigation (ODI) notice as having a front brake caliper problem. Since National RV is no longer in business, they are of no help in getting information about the investigation. To complicate matters, we are traveling in Mexico in the state of Vera Cruz. So we would appreciate any technical advice you can give us.
Peter Michelsen, F255982, Peru, Vermont
According to a representative from Workhorse, the ODI campaign is investigating a front disc brake caliper overheating issue and poor brake performance on brake parts manufactured by Bosch that were used on Workhorse W20, W22, and W24 chassis. The campaign also involves numerous other trucks, buses, and motorhomes that used the Bosch calipers through 2003 VIN 356806 (2004 chassis models were not involved in the campaign and have the latest calipers). However, there is an open NHTSA investigation (no conclusions at press time) on units built with the improved caliper.
The Bosch brakes are very common. International (Navistar) uses the same caliper on a number of models, including school buses. Although Workhorse does not have any service centers in Mexico, the Workhorse representative suggested that you look for an International Truck dealer in Mexico. Most large International dealers would have the caliper and other parts needed to fix the brakes.
Overheating the brakes can bring on the problem. Drivers should be careful to use engine braking so as to not overheat the chassis brakes. Brakes should never be held on for more than five or 10 seconds, and then only hard enough to slow the vehicle to make a downshift.
Pumped Up
Your article on air compressors, “Pumped Up,” which appeared in the April 2009 issue (page 46), was informative and appreciated. It never occurred to me that I could use the on-board air compressor (for air brakes and suspension) for winterizing the RV’s plumbing. There are times when this would be convenient. For example, when returning home from a mid-winter trip I could blow out the water lines while I’m still in an area with above-freezing temperatures. However, I would be concerned about subjecting the plumbing to the more than 100 psi of pressure produced by the on-board air system. I use a pressure regulator to restrict water pressure to 45 psi when connected to a campground water supply. Could this regulator be used to limit the air pressure to 45 pounds when blowing out the water lines?
Keith Lynn, F182219
Swansea, Illinois
I am not well educated on the design limitations between pneumatic and hydraulic pressure (and volume) regulators, but a wild guess would be that they are nowhere near the same.
I suggest that you purchase a pneumatic regulator, rather than take a chance with the hydraulic one you have, and set it between 45 psi and 60 psi. Also, for what it is worth, it’s my opinion that air pressure does not do a good job of evacuating the water, as it leaves a film of water on the walls of the tubes, which later will accumulate at a low point. NEVER use air pressure to winterize the Aqua-Hot heating system, per instructions from Aqua-Hot.
Desiccant Cartridge
I have a 2002 Holiday Rambler 38-foot motorhome. I have a question regarding the desiccant cartridge on the Meritor WABCO air dryer installed in my motorhome, which has air-over-hydraulic brakes. The maintenance manual states that the cartridge should be changed every two to three years. Is it necessary to change the desiccant cartridge if there has never been any water in the air storage tanks when I drain them? What are the consequences of not changing the cartridge?
Thanks for this column in Family Motor Coaching magazine. It is a must-read for me each month.
Alan Hawkins, F330457
McDonald, Tennessee
Perhaps the reason you don’t see any water when you drain the air tanks is because the air dryer is doing its job. However, if you don’t change the cartridge on the manufacturer’s schedule, you’ll be taking a chance that water will collect in the air lines, which could lead to corrosion and potential brake malfunction. The reason the company recommends changing the cartridge every two to three years is the relative differences in humidity from one region to another. If a vehicle is used in an area with high humidity, the cartridge should be changed at the early end of the interval. For vehicles used primarily in low-humidity areas, the cartridge should perform fine for up to three years.
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