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Topic: Narrowing the Air Leak Search (Read 993 times) previous topic - next topic

Narrowing the Air Leak Search

I have searched the topic, "air leaks" and my head is spinning with all the places that air leaks on these machines.  I am hoping that given my symptoms someone can point me toward what areas are more likely culprits or what areas are highly unlikely problematic, thus narrowing my search. 

My symptoms: When I shut the engine down after a trip the gauges for both front and rear tanks drop precipitously (one pound every minute or two) until it reaches about 50psi.  At that point the pressure in both tanks holds and only loses a pound every hour or two, requiring several days to go all the way to zero. 

I have sprayed soapy water on various locations to no avail so any guidance would be appreciated. 

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Narrowing the Air Leak Search

Reply #1 –
I would say you probably have two leaks if both the front and rear tanks are going down.  The leak has to be after the protection valve that cuts off the air to auxiliary items at around 60 psi to insure enough air for the air brakes.  Looking at my air diagram the possibilities for the rear air tank are the air lines to the retarder accumulator, air hose quick connection for tires, and rear HWH air bag manifold,  For the front the possibilities are the front HWH air bag manifold or the regulator to it.  One thing that could cause both tanks to leak is a bad check valve at HWH compressor allowing the air in tanks to back feed to compressor and leak somewhere there, assuming your year coach is tied into the HWH compressor, not all are.
2002 36' U270 Foretravel

Re: Narrowing the Air Leak Search

Reply #2 –
This is assuming both check valves on the front and rear tanks are in working order.  You can check this by opening the water drain valve on wet tank (the air tank near rear wheels) and see if one or both tanks' pressure falls.  If they don't fall the check valves are good if one or both fall then you will need to replace the check valves on your tanks before you can narrow down where your leaks are coming from.  Since you say it holds pressure after 50 psi the check valves are probably good, but I would start there first.
2002 36' U270 Foretravel

Re: Narrowing the Air Leak Search

Reply #3 –
You really can't safely go under coach to check for leaks without safety blocks.
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: Narrowing the Air Leak Search

Reply #4 –
A pressure gauge that reads the wet tank pressure can be useful in these situations.  I have one in my engine compartment that is connected to a unused RES port on my D2 governor.  Another handy place to attach a gauge is on the end of the tire filler hose (assuming that hose comes directly off the wet tank like it does on my coach).

Comparing wet tank pressure action to the front and rear brake tank pressures can sometimes help identify faulty components.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Narrowing the Air Leak Search

Reply #5 –

I just replaced six check valves and both pressure protection valves.  There is definitely a leak at the step cover slide controls that will be very hard to fix so I am adding a NC 12v solenoid valve at the tank to close that line (39)  when ignition is off.  I attached a copy of my air system schematic.  Yours will be similar except for the slide parts.

I have found this to be pretty effective at detecting leaks
Amazon.com: Snoop Leak 8OZ-Snoop Snoop Leak Detector, 8 oz.: Industrial &...

Use pipe thread sealer rather than tape.  Something like this.
Amazon.com: Rectorseal 23631 1/4 Pint Brush Top T Plus 2 Pipe Thread...

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Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Narrowing the Air Leak Search

Reply #6 –
On our 99 270 found some air leaks and still had a pressure drop, went to H&H who discovered that the 6 packs were leaking and needed all new O-ring rebuild kits. Problem solved, might want to give the 6 packs an extra squirt of leak detector
David & Emma Roche
Dino (Golden Doodle)
1999 U270 WTFE 36' Build # 5534
Xtreme "Lights, Stripes & Roof"
Motorcade# 18321
Dayton, Ohio
Towd: Jeep Grand Cherokee
Two Townie Electra Bikes

Life is made to enjoy, the Foretravel helps!

Re: Narrowing the Air Leak Search

Reply #7 –
Quote from: "Irish" –
The m out 99 270 found some air leaks and still had a pressure drop, went to H&H who discovered that the 6 packs were leaking and needed all new O-ring rebuild kits. Problem solved, might want to give the 6 packs an extra squirt of leak detector
I found one of my front 6 pack was leaking using a ultrasonic tester.
Steve

1997 U270 36' build 5179
Motorcade #18147
1980 CJ5

Re: Narrowing the Air Leak Search

Reply #8 –
I have now located three air leaks, two minor and one more significant.  The larger one is on some kind of a valve on the port side forward air tank.  This valve looks generally like a propane regulator.  Pictured here, it has a pressure release port on the right end where the numbers 59DG and 348K are located.  Besides air coming out there, it is leaking out the sandwiched area where it appears to me there is an internal diaphragm.  I located this item on my air system schematic where it is labeled "H" but I cannot find a key which tells me what "H" is. 

So, I need to know the name of this item so I can replace it.  Thanks in advance.

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Narrowing the Air Leak Search

Reply #9 –
Richard,

They are protection valves. Here is a link to look at. 
90555396 - Pressure Protection Valve - Haldex product

Your  replacement P/N should be 90555396 or the 9055399 (the old number) There are some cheep knock off out there if you look around BUTTTT???

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Narrowing the Air Leak Search

Reply #10 –
Thanks Mike,

I followed your link to the Haldex web site and found a distributor near where I am camped in Rhinebeck, New York.  The facility was a truck service center and Cummins rep.  Although the parts department had computers, when I gave the parts guy the parts numbers you gave me, he pulled out the old paper Haldex catalogue.  On the one hand it was nostalgic to see the six foot long row of catalogues, on the other hand I had my doubts about the place being in the modern world.  The part numbers did not match any he had. 

If I had had the opening and closing pressure requirements, I might have been able to choose l the proper Pressure Protection Valve.  As it was, I just thanked him for his time and left.  I will try again somewhere down the road.  My pressure bleed-down is still twice the minimum DOT requirements. 

So now the question is, "What should be the correct the opening and closing pressures?" 

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Narrowing the Air Leak Search

Reply #11 –
Richard,

After a phone call or 3,  I found out that the newest number that is used is  90555400.    If you look on eBay there are several listed of both numbers. Pressures should be #65 open #70 close.    Make sure that you get ones with 1/4" NPT.

Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Narrowing the Air Leak Search

Reply #12 –
Thanks again Mike.

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
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Re: Narrowing the Air Leak Search

Reply #13 –
Here is the pdf ftom haldex
Shows part numbers and closing pressures
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: Narrowing the Air Leak Search

Reply #14 –
These are available at napa. My local napa had to get it overnight, at $45.  If you have more time, I ordered 2 more on ebay for $25 each.
Napa was able to cross reference the old number with the new haldex part #90555396 with no problem. So far, napa has been able to get everything I have needed overnight.
Kathy
05 36' U270
 

Re: Narrowing the Air Leak Search

Reply #15 –
Quote from: Roger & Susan in Home2 –
I have found this to be pretty effective at detecting leaks
Amazon.com: Snoop Leak 8OZ-Snoop Snoop Leak Detector, 8 oz.: Industrial &...
X2 on Snoop Leak

see ya
ken
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