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Air Dryer Bypass Demo

NOTE:  If you are unfamiliar with the air dryer bypass tool, see this topic:  Air won't build past 40psi, stuck by roadside

Don and Tys (acousticart) recent roadside experience with a malfunctioning air dryer was a wakeup call for me.  I decided I would go through my air system and replace or repair any questionable components, and in the process familiarize myself with the procedure required to use the Emergency Dryer Bypass (hereafter referred to as the EDB).  Those of you who have never had a dryer go bad may assume that using the EDB is pretty simple - you just remove the air lines from dryer and connect them.  Well, after simulating a "dryer failure" in my driveway (with safety stands in place) and attempting to use my EDB, I can tell you that it may not be quite that easy.  In fact, for me it was VERY difficult!  My sincere congratulations to Don for being able to accomplish this task under less-than-ideal conditions!

Your first problem will be access.  I know different model coaches have the dryer mounted in different places - yours may be easier to reach than mine.  Dryer failure usually means no air pressure, which means no lifting the coach to install safety stands.  My AD-9 air dryer is mounted high up in the driver side rear corner of the engine compartment, hidden behind one of the hydraulic tanks.  Reaching in through my engine cover, I can only touch it with one hand.  Crawling under the coach is the only realistic way to work on it, but with the coach sitting down on the mechanical stops, you will have very little room to maneuver.

Your second problem is tools, or rather lack of them.  I carry a pretty good selection of tools in my coach, but I only had one wrench that was big enough to remove the big air line connections: a 12" (300mm) Cresent wrench.  A adjustable wrench is not ideal when faced with VERY tight connections, but it will work.  Personally, I plan to buy several properly sized open end wrenches, so in the future I will be better prepared.  A couple 1 1/4" heavy duty spanners should do the trick.  A 2' "cheater pipe" would also be very helpful!

You will need some way to plug the small "control" air line that runs from the D-2 air governor to the air dryer.  It will probably be either a 1/4" or a 3/16" flare connection - I would carry both size plugs (or a selection of sizes) just to be safe.  See the photo of the required flare plug (below).

There has been some discussion recently about the "shape" of the EDB.  Some say a simple 1-piece double union connector would work.  In my case, it would not.  There is no way I could bend the big air hoses enough to make a straight connection.  Only a "U" shaped bypass would work for me.

On to the demo!  The photos below (hopefully in order) will show the following:

1.  AD-9 air dryer viewed from the engine hatch.  The small braided "control" hose just visible to the left of dryer is the one you need to remove and plug.
2.  Close up of small braided "control" hose.  The flare plug goes here.
3.  Photo of type of flare plug that is required.
4.  AD-9 air dryer viewed from under the coach.  The 2 big braided hoses (one in foreground, one in background) are the ones to remove and connect together.
5.  Big hoses detached from dryer and connected with EDB.
6.  Better view of "control" hose connection.  There is a "T" double flare connection at the base of dryer (below the white label).  Control hose connects to the "T".

Re: Air Dryer Bypass Demo

Reply #1 –
GREAT POST CHUCK !!!

Re: Air Dryer Bypass Demo

Reply #3 –
Chuck, thank you ^.^d

How often could this happen?

If its more than every 3-4 years; would it be possible to install a perminate bypass?

Re: Air Dryer Bypass Demo

Reply #4 –
Nice Job Chuck! ^.^d
Don

Re: Air Dryer Bypass Demo

Reply #5 –
 Chuck,
Great follow-up! 
On your coach, is the D-2 Governor easily accessible?  It doesn't matter which end of the pneumatic Governor "control" signal is plugged, as long as the Governor air escape is terminated.  On my coach, the Governor is very accessible.  Removing the flexible tubing (headed toward the Haldex Pure Air Plus Dryer) and using an 1/8" NPT plug in the Governor "control" port is the easiest way.
Thanks.  Very nice.
Neal
 

Re: Air Dryer Bypass Demo

Reply #6 –
 Now your turn Neal to beat me to it on posting about removing the D2 line and plugging.
I bought Friday the fittings to make a bypass etc "just in case" even though I regularily service the Dryer (every 18 months)  and hope never to need to use the "rescue kit" !!
Luckily the location of Dryer on our coach is very accessable on the rear crossbeam that contains the hitch, although you still have to get under this tube to undo lines.
Good posting Chuck.
JohnH

Re: Air Dryer Bypass Demo

Reply #7 –
Very informative and helpful post, including the need for proper tools.
Thanks,
Rodger

Re: Air Dryer Bypass Demo

Reply #8 –
Quote from: Neal Pillsbury –
On your coach, is the D-2 Governor easily accessible?

On my coach, it would be a toss up.  The D-2 is hidden behind the other hydraulic reservoir, on the passenger side of the engine compartment.  It would be equally easy (or difficult) to disconnect the hose and install the appropriate plug at either end of the "control" hose.  Might depend on what kind of plugs you have available, male NPT or male flare.  I will be adding a selection of both type plugs to my tool kit!

Re: Air Dryer Bypass Demo

Reply #9 –
Quote from: fouroureye –
...would it be possible to install a perminate bypass?

Almost anything is possible!  Would it be worth the effort?  Only you can answer that.  You would need 2 valves, one at inlet and one at output, on the dryer.  Then between both big hoses and the valves, you would install "T" connectors.  A cross pipe (or hose) with another valve in the middle would connect the 2 "T"s.  All these fittings would have to be fairly large gauge, to match the size of the air hoses.  Finally, you would install a small valve somewhere in the "control" line.

Normal operation: The "control" line valve open, the valve between the "T"s closed, and the dryer inlet and output valves open.

Emergency operation: The "control" line valve closed, valve between the "T's open, dryer inlet and output valves closed.

Give it a try, and let us know how it works!

Re: Air Dryer Bypass Demo

Reply #10 –
Chuck, how often is the possibility a EDB would be needed?

Re: Air Dryer Bypass Demo

Reply #11 –
Quote from: fouroureye –
Chuck, how often is the possibility a EDB would be needed?

One of those questions that is impossible to answer - maintain your air dryer as recommended (by the manufacturer, and on this forum) and you may never need one.

Re: Air Dryer Bypass Demo

Reply #12 –
Thats what i thought, but there are "gear heads" here like Don. If it happens to him and since i dont have his "roadside" skill set it, this is a good option that I need to consider.

I am at best an amature, my Dad is expert but 85 so looks like a hundred or so in the drive will probally net save $300-500 plus a tow, time, frustration etc, etc :o

Thanks Chuck! ^.^d

Re: Air Dryer Bypass Demo

Reply #13 –
Wow, nice write up.

Larry

Re: Air Dryer Bypass Demo

Reply #14 –
Howdy Chuck,
    Great write-up!!  I bought the fittings to make an EDB, and I'll be getting a set of the large wrenches.  Thanks for the link to HF. 
Thanks for all your great work on this issue.  Dave A

Re: Air Dryer Bypass Demo

Reply #15 –
Thank you!!!
I'm especially glad to learn about that small control line from the D2. I was confused about it until now.
Just a question about the large wrenches... a few days ago Roger Berke of Aquahot posted a HF link for some as well (15 Piece SAE Service Wrench Set). You mentioned a 2' cheater pipe, so I'm wondering if the pipe would be easier to use on this other set. Just curious about your opinion on which set. The price is the same; Roger's set only goes up to 1 5/8" though. Would that be big enough?
sure appreciate your photos!
Thanks, Dick

Re: Air Dryer Bypass Demo

Reply #16 –
Went to Home Depot and Lowes and could not find the parts to make the EDB.  Will be in Nacogdoches on the 11th of this month so will go by the hydraulic shop on the loop and see if they have the parts.  Can you give me again the list and size of the parts.  They have been mentioned here in so many sizes I am now confused.  Are there more than one size air dryer?  DAN

Re: Air Dryer Bypass Demo

Reply #17 –
 For me, when I serviced my first air dryer and didn't have wrenches big enough to do the job, instead of buying a set of large wrenches and most likely using only one or two of them, I bought a Hex wrench from Ridgid Tools. It's about 10 1/2 inches when fully opened, jaw size is from 1 1/8 to 2 1/2 inches. You don't have any hose fittings larger than that on our coaches. You will have to use a "cheater" pipe with it for the big fittings.

Re: "cheater" pipe "

Reply #18 –
I carry three(3) different size PVC pipes, about 18" long
They are labeled " Cheaters, do not remove "
Easy to cut off if they are to long to use, replace when you get home.
Save the old one too.

Re: Air Dryer Bypass Demo

Reply #19 –
Quote from: rbark –
I bought a Hex wrench from Ridgid Tools.

We used to use those in the oil field - it's a good tool (as is everything from Ridgid).  We would put too big a cheater on them, and bend the handle.  Ridgid would replace with a new one, no questions asked.  Only concern I would have is the size of the wrench versus the working space available.  I think you might run into situations where this adjustable wrench would not fit, but a standard open end would.  Best idea would be to have both!  Remember the old saying: "He who dies with the most tools, wins!".