Well... I don't know how it got away from me, but I,ve not thought to check/change the desiccant cartridge and coalescing filter on the air dryer for some time, and had a hell of a time getting the coach home recently. (That's a story unto itself, but I'll spare the details.) The bottom line is that when I removed the old desiccant cartridge, it looked like a large container of talcum powder had been poured into every port, inlet, and crevice, and then hosed down with a healthy spray of water. IT WAS A MESS!
I had some problems changing out the relieve valve from Desiccant Kit # DQ6026, but other than that, things went better than I would have expected for the first time.
But after getting it all put back together, I'm getting a constant air leak from the purge valve on the very bottom of the dryer. After looking at the trouble shooting guide on Barry Beam's website (THANK YOU BARRY), the problem appears to be a damaged purge valve seal, or perhaps just foreign particles on that seal. At any rate, I' guess I'm going to have to take that Purge Assembly appart, and probably replace.
It can be changed on the coach, remove black plastic cover on the bottom, than remove retaining clip and purge valve will come out.
I already had the plastic cover off. I was having a heck of a time getting the snap ring off. It had evidently rotated into a position that would not let me use the snap-wring pliers. I got frustrated enough that I ended up disconnecting the air hoses and removing the air dryer.
I went ahead and removed the old Purge Valve and clean the chamber since the sun was shining this afternoon.
I used patience, a can of aresol degreaser, and paper towels. I was reluctant to spray the degreaser into the purge valve housing, as I was concerned that it would drain further into the air dryer. So I tore off small pieces of paper towels, saturated them with the degreaser, and used a small screw driver to work the paper towels into the edges and corners of the housing.
It was slow and tedious, for sure, but I feel pretty good about getting all that grunge cleaned out.
Air Dryer (bottom) before w purge valve
Air Dryer (bottom) w-o purge valve
Air Dryer (bottom) with purge chamber cleaned
I was able to pick up the DQ6020 (Major Repair Kit) from NAPA this AM and will try to further disassemble the air dryer when it warms up.
HOLY COW, was it a mess! No wonder it didn't seat and was leaking air.
Posting some before/after cleaning in case any one who has not torn into their air dryer might be curious as to what it's NOT supposed to look like.
My AD9 has at least 8 nuts at the base, and 2 wide bands around the cannister that have to be loosened. In our coach, the dryer is tucked away in the far passenger-side corner of the engine compartment behind the hydraulic reservoir for the power steering pump. The only way to get clear access to the dryer is to drop it out of the bottom of the compartment. Not an easy task in the '92 U-280.
My impression has been that the outer cannister just protects the other components (heater, dessicant, purge valve, etc.), so I don't know why it would hurt to open it up, but again, others on this forum are more qualified to answer this. Don Hay 1992 U280
Turns out I have a Haldex Pure Air Plus in my 1999 U-270.
It took a turn for the worse a few weeks ago and started sounding
like a gun going off in rapid fire. It was a little disconcerting.
Figured that reliable air was a good thing to have on a coach with
Air suspension and brakes. So we called Haldex and they felt
that the unit needed to be rebuilt. They were very helpful and
suggested that if we were to do the job, the rebuild it ourselves was
the way to go. If we were having a shop do it, they said buy a new
one and have them do a remove and replace. It would probably work out
to about the same total cost than buying the rebuild kit and paying
the labor for a mechanic to rebuild it.
So with my trusty friend Bob Cramer we took on the job
yesterday. A little intimidating since everything was old, rusty, big,
and covered with grease. Plus if we didn't get it done right,
't have air, and therefore probably wouldn't be able to move.
Here is what we (Bob Cramer and I) did yesterday in about 5.5 hours
(BTW, last week I cleaned bottom of the coach with Solvent
sprayed with on with compressed air. I bought sprayer and solvent.
Menards- sprayer was $11 and the solvent (mineral oil basically) was
$38 for 5 gallons. I used about two quarts. Then I put "Mouse
Milk" on everything that needed to come loose. Mouse Milk is a great
penetrating oil used in aircraft industry (Chief Aircraft
Parts always has it in stock - get some) in preparation for
With some trepidation, off we went, chocked front and rear
wheels, and then used air suspension to pick up rear of coach - then
blocked it up with wood 4 x 4's to keep it up for sure.
On my coach there were four 9/16 head bolts holding the unit
to the coach with 7 different air lines connected to the unit. Mark the
lines in some fashion - colored tape, etc., take a picture,
draw a diagram so it will go back together easier. We didn't and I
ended up reversing the main air lines at re-install. It didn't hurt
anything, but wasted 45 minutes figuring it out and switching.
BTW - The rebuild kit lists for $55 or so. I bought it online
for $44 and $5 shipping. (New Dryer is $299 and a rebuild I saw on
line was $229). This of course does not include the expensive filters,
Found system drain in front of drivers side rear tire and drained system.
I fought the little sucker out of the coach (clearly the
hardest part of the job - rust, rust, rust)
This took about 3 hours and some ingenuity, hammers, a big
pipe, the 1 1/14 wrench and three pipe wrenches. The two large air
lines were the biggest issue they were very rusted, especially the
input side as you might imagine since it was the "wet" compressed
I carefully followed the instructions on the rebuild kit and
rebuilt the unit changed out the parts in three different areas of
the dryer (really well written and easy to follow instructions. If
you get to the rebuild part, you will be able to successfully get this
job done. It is more of a light disassembly and reassembly with
a few new parts and o-rings.
Going back in was the easy part. (Except if you didn't
make a sketch or take pictures so you would know which direction
the fittings faced, etc.) Next time we will take pictures and a
diagram. It is pretty hard to screw up, it just took a
little more time to get the fittings facing the right direction,
and all the lines back where they belong.
Once we did that and started the coach, did the
"operational check" per the instructions, which is let the pressure
build and when it reaches the upper limit, and fairly loud burst of
air comes out followed by about 30 second of air hissing.
All good and coach is back in service.
Hard stuff in this job.
Dealing with rusty lines - needed ingenuity to get them off.
Some while still on coach, others after we got it partially
out.The two big ones required 1 1/4 inch wrench. If you have that
and a few pipe wrenches, a piece of pipe to increase leverage, and
typical sockets, pliers, screw drivers, vise, bench you have the
tools you need. You also could use a set of snap ring pliers. Not
everyone has those , but we ended up using a pair of needle nose
Tight quarters to get work done.
Grease and dirt everywhere and everything you touch..
Figuring out how to block up coach - used air suspension -
(check valve holds up airbags even when no pressure on system, and
I actually fit well under the coach - but wouldn't want that
Not sure "Diesel mechanic" title is for everyone - but
thanks to my friend Bob Cramer we "got her done" Tim Fiedler 1999 U270 7/07
A couple of important things we can comment on based on our (Steve's) experience working on the Haldex air dryer on our 2003 U320.
To change the filter, you will need to dump the air completely out of the coach. No air brakes, no air bags, no air anything. Make sure you are level, CHOCKED, and have completely dumped the air out of the air bags first. Steve dumped the air using the front "air dump" switch, then opened all the valves around the coach.
The filter itself comes off just like an oil filter.
There was also a coalescing filter that fits down the middle after you unscrew the main filter. It pulls straight out for replacement.
Steve says it will take longer to fully dump the air than it will to replace the two filters. Ours also came as a kit with instructions. We got it from FT parts, who had the best price at the time we were shopping. Michelle & Steve 5/16/2009
The filter spin on and coalescing filters cannot be salvaged. You would not
want to take the chance of getting junk in the brake lines. Also while
rebuilding the my unit (1995) I found that some parts had been upgraded.
Since I now know that mine is completely clean, and working correctly, next
time I will just replace the spin off filter kit and not have to completely
remove the unit and fight a huge fitting with a large pipe wrench to replace
the internal parts. About a day after I did mine I found that the entire
unit can be purchased rebuilt for about 50.00 more that the three kits cost,
so for the less technically determined individuals I believe the already
rebuilt unit is the way to go. Since the unit has to come off to replace
the pop off valve anyway. But if your only needs the filter, then the
filter kit is the way to go. But I would imagine that anyone with a vintage
of 2000 or older really should rebuild the entire unit, not just replace a
filter. Each kit came with the necessary instructions and all grease and
seals was included. Greg Jones 1995 U280 5/17/2009
Cummins South called and told me I could bypass the dryer as see if air would build up to test it. Couldn't do that, but I was able to disconnect the two large hoses. Started the coach back up and I was getting good air 'chuffing' out the compressor outlet hose. I'm now much more satisfied that the air dryer is indeed the culprit.
FYI, the Cummins guy said the most they almost ever have to do on a compressor is replace a head.
Spoke to Derek at MOT he advised me to also get the lower repair kit
Dave Head 95 U320C SE 40 1/4/10
At a past Foretravel Mid-South Rally in Amarillo, TX; one coach had a similar problem. The air dryer had not been changed and thru time and aging the internals blew up, plugging the system; it was a mess with desiccant powder distributed throughout the RV’s air system.
James Triana was attending the meeting to give his technical presentation; he changed it to the air dryer system (Haldex) and shared with everyone the system is overlooked and should be changed on an annual basis; as part of the repair / replacement kit is a pop off valve, the gaskets, the desiccant, etc. As I recall both John, Jack and James were working to pull air lines and trying to purge desiccant powder from them – it was a mess.
You will need a ground down (thinned) open end or boxed end (best) wrench to remove the unit; I cannot find my notes from the meeting, but John Hughes was the person who changed unit out which was on a ‘95 coach. I remember this since I had a ’95 coach at that time.
You will need a thinned down wrench. I do remember that much from when John Hughes showed it to me. The wrench size was removed but I think it was 9/16; Triana can confirm.