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Topic: Air Dryer By pass (Redux) (Read 814 times) previous topic - next topic

Air Dryer By pass (Redux)

Back in August there was a thread on Air Dryer By Pass kits Air Dryer Bypass Demo prompted in part by Don's Canadian experience.

Having just had fun times in a parking lot Another Air Problem I thought I'd pass on some of my observations.

Observation #1
There appear to be enough variants of dryers and their associated plumbing that a 'one-size fits all' kit will only work if you know what 'size' you are.  On mine there are at least 4 connections in addition to the two big ones.

Observation #2
Related to Observation #1. Since your dryer may be configured differently from those pictured and/or described on other coaches, a detailed plan is necessary. I think Chuck was right when he said he wanted to do a dry run.

Observation #3
I carry a couple of big tools but they would have been completely inadequate for the task on my coach. I have seen some coaches that boast a reasonably accessible dryer. Mine is not one of them. It sits above the skid protecting the end of the engine. There was very little room to 'twist' anything.

Observation #4
Certainly, collecting the critical fittings is worth doing. Collecting the necessary identification of the crucial steps is worth doing.
For me concluding that I will probably have to have a 'wrencher' along side is worth doing.

Your mileage may vastly differ.
Elliott & Mary Bray
ex. 1996 36' U295 - Build 4879
ex. 2018 Coachmen Leprechaun 319MB
 

Re: Air Dryer By pass (Redux)

Reply #1 –
I just had a new air dryer put on, and at one point BOTH of the mechanics were on one connection, trying to break it loose. The both had pretty large wrenches in their hands, too, much larger than anything I have. I'm sure glad those two young guys were able to break it loose. I'm afraid to crawl underneath and see if they put things together as tightly as they found them.

Re: Air Dryer By pass (Redux)

Reply #2 –
When I replaced mine, the fittings came lose pretty easy (big wrench) but when I took out the two 90's I had to brake out the tourch to heat them up a bit.
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Air Dryer By pass (Redux)

Reply #3 –
It is ridiculous to over tighten JIC fittings >:D
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Air Dryer By pass (Redux)

Reply #4 –
Aren't the 90 degree fittings NPT pipe thread into the air dryer which can be pretty tight? JIC is the flare on the other end of the 90's, which loosen easily?

Re: Air Dryer By pass (Redux)

Reply #5 –
The air dryer's JIC fittings were pretty tight, but I was able to do it with very little clearance from under the coach with an open end wrench. I won't say it was easy, but they had been on probably since new and perhaps a bit of oxidation thrown in. The other side of those 90º fittings were ½" pipe thread, and it was another matter altogether to break those loose so I could use them to make a bypass by the side of the road. However, the good news is that you won't need to extract those 90º pipe thread fittings out of the air dryer if you put together the necessary parts to make a bypass ahead of time.
Don
Quote from: rbark –
It is ridiculous to over tighten JIC fittings >:D
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Air Dryer By pass (Redux)

Reply #6 –
Yes Barry they are,  and will leak if not tight :o
Andy & Eileen
MONTROSE COLORADO
1992 U300  40' 6V92 TA
2016 4 Runner
1998 Jeep Grand cherokee

1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: Air Dryer By pass (Redux)

Reply #7 –
You are right about the NPT fittings Barry, also should always use a thread sealant for those, but not on JIC, they should be dry.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Air Dryer By pass (Redux)

Reply #8 –
I thought one more missive re: Dryer By-pass was in order

Now that I have paid someone to swap out my Air Dryer I don't expect to ever have to worry about it again (said with shy sideways slump and hands in pocket- kinda like a rotund Will Rogers).
However, I realized that I didn't know enough about the system, particularily about the system installed on my 1996 U295.

Disclaimer: 
From previous posts it seems that different year coaches have different 'boxes' installed but I think the principles are the same and many coaches are 'wired' the same. 

General Principles:
There is the Wet tank which is pressurized by input from the Air Compressor via the Air Dryer.
There is the Air Compressor which feeds the Air Dryer on orders from the Air Governor.
There is the D-2 air governor which accepts compressed air from the wet tank and tells the Air Compressor to either generate more compressed air or not depending on the governors programming and the air pressure in the wet tank.

Specific to my (and several other)coach:
There is also a brass fitting which sits between the main air line from the compressor and the dryer called an ECON Valve.

Aside:
I once installed a 15 rank Reuter electro-pneumatic pipe organ in my living room. The more I look at this the more they look the same.
If compressed air is on both sides of a diaphragm nothing happens. Allow one side to exhaust to atmosphere and  a valve gets opened.
I give you this tidbit for free.

Explanation of attached Drawings
I have attached two copies of an abstract from Foretravel Drawing B-2036 (U280-U295  E21 Air Schematic)
The lines in Blue are compressed air
The lines in Red are open through the D-2 Exhaust port to atmosphere.

Drawing #1 The status prior to reaching the Cut-Out pressure as defined by the D-2.
Obviously then once Cut-out is reached, things settle down until enough air has been used from the wet tank to go below the Cut-In (the lower) pressure.
Drawing #2 Shows that the D2 has now quit accepting compressed air from the wet tank and  has opened the 'Unloader' lines to atmosphere through it's exhaust port.

Note that both the ECON valve and the Air Dryer share a line from the D2. More later.

Look at the ECON valve in drawing #2. The way I read it, when the Air Compressor is instructed to take a break, pressure from the wet tank is probably on one side of a valve and atmosphere is on the other (through the unloader and hence through the exhaust port).This now 'isolates' the Air Dryer from the Air Compressor - something Cummins felt was a good thing (beyond the scope of this thesis). Not surprisingly the ECON valve is also called the 'Isolator' valve.

Conclusion (at last):
So now I think I know the theory behind how to by-pass the Air Dryer on my coach rather than relying of a cookbook written by someone whose system might be different.
I suspect it applies to the coaches that have the external ECON valve.

In addition to connecting  the large 5/8" hoses (boxes 1 and 2 on the drawing) I think I would cap off the 1/4" line (square 3) from the air dryer and also the 3/8" (square 60) from the ECON valve.

At least, I might acquire the parts to do this. I'll still have to think about the tools and muscle.
hth

OBTW My resonator reminds my of an 8' Vox Humana
Elliott & Mary Bray
ex. 1996 36' U295 - Build 4879
ex. 2018 Coachmen Leprechaun 319MB