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Old 09-08-2019, 10:06 PM   #1
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Surprising failure of Bendix AD-IS mounting bracket almost left me stranded

I'm a little embarrassed that it took me 4 years to find this problem. Fortunately it didn't leave me stranded, because I fixed it in time.

Most of our coaches have a Bendix Air Dryer Integrated System (AD-IS). This is the unit that removes moisture from our compressed air to avoid corrosion in crucial parts like brake systems, air tanks, and apparently even the DEF dosing system.

I was greasing the drive line of my coach and noticed that a large metal can was rubbing against the universal joints of the drive shaft (going over bumps, I guess). I noticed that a strap was supposed to hold it in place, and it was missing. Looking at PartsPro, the item comes with an Air Dryer Mounting Bracket Clamp Kit BW 5002080. Initially, I thought I only needed the clamp, but it seems that I had to buy the brackets to go with it. But, when I set about installing the clamp, I realized that the lower mounting bracket was broken on one end and cracked on the other. I attach a photo for your interest. Looking at the corrosion around the cracks and break, it looks like the problem dates back to the original delivery of my coach. The part is made by Bendix.

What would happen if the drive line had ruptured the AD-IS can? Well, I would have lost air in my system and the air pressure would have fallen. Warnings of low air pressure would sound, and eventually, the emergency parking brake would engage. So, when the warnings sound, one should park the coach in a safe place before the parking brake kicks in.

The problem is even worse, because this is the point where there is a Schrader valve that is presumably used by tow truck drivers to put air into the system and keep the emergency brake from engaging while they tow. They wouldn't be able to do this if the AD-IS can is leaking. They would have to go with the official procedure of "caging" the parking brakes. It's in the air brake manuals, but I've never heard of anybody who had a tow truck driver who had to do this.

Why am I embarrassed about this? Replacing the AD-IS desiccant cartridge is an annual chore and I've never done it. I would have noticed the problem if I had changed the cartridge, which I did on the weekend.

–Gordon
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Gordon Sick, Calgary
2015 Berkshire 34QS
The Manual I wrote for our 34QS:
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2005 Acura EL (aka Honda Civic)
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Old 09-08-2019, 10:19 PM   #2
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Quote:
Originally Posted by gordonsick View Post
<<<<<So, when the warnings sound, one should park the coach in a safe place before the parking brake kicks in.>>>>>


<<<Why am I embarrassed about this? Replacing the AD-IS desiccant cartridge is an annual chore and I've never done it. I would have noticed the problem if I had changed the cartridge, which I did on the weekend.>>>
Yes, when the horn goes off you get off the road. My CDL instructor mercilessly beat that in to me......

You sure filter replacement is annually? I thought it was much longer. Have to research.
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Old 09-08-2019, 10:29 PM   #3
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Ah, you are right. It is to be done every 36 months or 45,000 miles. It is MOP 42-03 in the Freightliner RV Chassis Maintenance manual.

So, I was only 12 months late. I'm not such a delinquent owner as I originally thought.

If anybody is under their coach doing maintenance, look near the drive shaft for a black can that is about 8" tall and 7" in diameter. Make sure there is a clamping band on top and the lower parts of the mounting bracket are in good condition. It sure looked like mine would have come from the factory like this.

–Gordon
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2005 Acura EL (aka Honda Civic)
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