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On the subject of air dryers

In over 10 years of owning, driving abd maintaining my semi truck 95 Peterbilt 379 Detroit Series 60. Driving over a million miles, Never have I had air dryer issues. I don't  hear about air dryer issues from other Truck owners either. No white dust,nothing. But on the Foretravel forum here it seems you guys have all kinds of dryer issues.White dust,dryers coming apart, governor issues,etc.
Why is that?
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: On the subject of air dryers

Reply #1 –
I don't know.  On my drier the mobile tech who helped me until midnight pulled out what he called the mounting screw for the purge flapper valve.  With it was what looked like the fractured boss that the screw attached to.  Since you can only get reman'd driers of this vintage, and I bet no one is replacing internal castings, we are living on borrowed time unless we want to convert our plumbing to use current drier designs.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: On the subject of air dryers

Reply #2 –
I'd love to hear this answer myself, as I never have any dryer problems on the small fleet of trucks we run here.  Never. 

My only guess is that everyday use is much better for a dryer than the occasional use of most of our coaches?

Chris
1996 U295 36' WTBI

Re: On the subject of air dryers

Reply #3 –
Quote from: bogeygolfer –


My only guess is that everyday use is much better for a dryer than the occasional use of most of our coaches?

Chris
I also believe that is the issue.

Roland

1993 U280 4341
2010 Jeep Liberty
The Pied Pipers

Re: On the subject of air dryers

Reply #4 –
Has to be. The driers were invented for the trucking industry with instructions to service YEARLY. Well, they run a minimum of 125K miles per year and we will probably not go 125K in our lifetime. A few might, but according to the instructions most of us should NEVER have to service them. Yet they still break.
1994 U280, Build 4490
Deming, NM.

Re: On the subject of air dryers

Reply #5 –
I think it's the old thing of use it or loose it.  With all the fleets I ran it was the hanger queens that required the most maintenance.  Everyday use equipment started right up and ran without problems.  No matter how well we looked after the stand-by and occasional use items they were the ones to give us the most trouble and bizarre ones at that.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: On the subject of air dryers

Reply #6 –
But aren't the air dryers that are failing Haldex driers? Has anyone had a Bendix drier fail on this forum?
Scott Cook
1991 U300 36' 6V92TA
Old Town Penobscot 16
1984 Honda VF1100C (V65 Magna)

Re: On the subject of air dryers

Reply #7 –
Quote from: stump –
In over 10 years of owning, driving abd maintaining my semi truck 95 Peterbilt 379 Detroit Series 60. Driving over a million miles, Never have I had air dryer issues. I don't  hear about air dryer issues from other Truck owners either. No white dust,nothing. But on the Foretravel forum here it seems you guys have all kinds of dryer issues.White dust,dryers coming apart, governor issues,etc.
Why is that?
Stump,

Pretty easy actually.

First major point;
The Pure Air Plus DA33100/N4250  was designed to be used where available space (volume) is critical and therefore it is a smaller overall package.  Being smaller, compared with most over-the-road-truck and newer air dryers (like the Bendix AD9 family of dryers), the Pure Air Plus has considerably less desiccant and its coalescing filter is much smaller.  So then, a smaller volume, plus intermittent use with long idle periods, plus less capacity to absorb moisture/petroleum products = earlier breakdown of the absorbent medium.

The Haldex /Midland Grau Pure Air Plus is also a fifteen (plus) year old discontinued technology and only reman'd units remain available, most of which have been reman'd MANY times, so the basic core may have numerous metallurgical weakness that would only show up in ultrasonic or radiographic NDE (which of course is never done).  Brett's core failure may have been associated with that, allowing control air to return to the D2's port that was continually discharging on two separate D2's.

Second major point;
motorhomers are different from truck owners/operators;  Motorhomers tend to fall into one of three groups; (1) DIY's that may know what they are doing or (2) may not know and (3) those that don't have a clue.  The first group is the overwhelming minority of all motorhome owners.
Conversely, a trucker's down time is usually painful, dollar or otherwise, so they pretty much take care of business.  They take care of the maintenance that will make the vehicle reliable and DOT inspectable; they regularly blowdown the service air tanks, they react to moisture and desiccant dust in the tanks, they service dryers when things aren't right, they lose time and income if they don't. etc.

Motorhomers may or may not take care of business, mostly not.  Many don't know where the tank drains are, don't even know where or how many air tanks they have, don't know what is normal blowdown indication, even good DIY's often don't know when the last air dryer service was done and certainly don't service the dryers annually or every 125K miles, whichever occurs first, IAW manufacturer's requirements.  Many defer taking care of business until the budget is more favorable or it just plain breaks.

Living in the arid Southwest regions eases service requirements.  Operating in high humidity conditions with long down times and low temperatures increases service requirements.

Our brake service air compressors receive their intake air from the engine turbo pressurized air plenum.  Desiccant that is consistently "swept" by turbo and compressor heated air on a daily basis (think OTR truck operated daily) will decompose less rapidly than desiccant that is moisture laden and only exposed to moving air for 30 minutes during a monthly exercise or worse.  Everything decomposes (oxidizes) and moisture is generally a catalyst.  Desiccant decomposes more rapidly in moist, low temperature conditions than in dry, high temperature (Turbo/Compressor heated) conditions.

So, what to do;  change over to a larger desiccant volume, newer technology, Bendix AD9 family series air dryer, travel more frequently, and take care of business (momentarily open the test drain cocks regularly and service your air dryer if you see ANY moisture/desiccant dust out of "wet" tank drains).  If you see moisture out of your front and rear (brake service) tank drains, your aux compressor desiccant is shot, so take care of it.  If your aux compressor runs more frequently than daily, you should be seriously considering taking care of air system leaks.

Neal



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Neal (& Brenda) Pillsbury
'02 U320 SPEC, 4200, DGFE, Build #5984
'04 Gold Wing
'07 Featherlite 24'
'14 Jeep Grand Cherokee Summit
MC #14494
Exeter, NH & LaBelle FL
Quality makes the Heart Soar long after Price is Forgotten

Re: On the subject of air dryers

Reply #8 –
Neal,

Thanks for your informative and well-written post. I went to Nac&Back overnight to MOT and serviced my Pure Air dryer and some other items. Your idea regarding the three different Owner Groups got me thinking about where I fit in. I am trying to move from Group Two (May Not Know) to the First Group. I find that I am evolving, albeit somewhat slowly, with the help of folks like you on this Forum and the casual education we can get from some of the talented Folks at businesses like MOT and other specialty shops.

Stump,

Nice way to get things going and start people thinking! Keep it up. Best! P
Paul & Kathleen
1995 U320c SE 40'
Build 4681 --Cummins M11 /17511
"That Irish Girl"
Red MINI " 40"

Re: On the subject of air dryers

Reply #9 –
Interesting post on this subject.  I change out my cartridge and screw on filter every year.  I have 182K miles on my coach so far.  I wonder if the coaches that have this happen have much less miles for the number of years. I know that for the most part my coach is run for at least a week a month and many times much more. I have been on the road for 6 weeks and moving most of that time.  I like to travel cross country so that explains a lot.   
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon
 

Re: On the subject of air dryers

Reply #10 –
Neal that makes perfect sense. Great post. This is my first motorhome, first 2 stroke diesel, a lot of firsts with this thing. Even though I have been working on engines, building them and repairing anything that can be repaired. I never looked at it in that aspect. I think I will research a AD9 dryer for mine It would be easier to service with a spin on cartridge. I think I can get a used setup from the truck salvage yard for cheap. I run one on my Peterbilt. I have plenty of room on my 91 for it to mount.I'll put it on my to do sometime list ,in the meantime other things other things to do, lets see...................'sigh' where to start.........
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit