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Air leak in Brake system


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Hello Group.

 If I connect compressed air to the air connector up front for the tow truck brake release, does this charge the chassis air system just as if the engine is running?

I have a massive air leak that has developed as the coach has been sitting. I need to diagnose and need to keep the system charged without running the engine if this is possible?

2000 Dynasty HWH leveling system. The air bags stay up for months so the leak must be in the brake system?

Thanks.

 

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Everything past and including dry tank will work as usual once you get enough pressure in. It will bypass the compressor, governor, drier and wet tank connections. Brake system, leveling will have air as usual.

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Yes it will release the brakes. Is that your goal?? I would leave parking brake on (no air to braking system whick locks braked) Then run engine and look for leak. If you depress brake peddel and the pressure doesnt hold it is in braking system. Dont use the Tow Truck connection or your coach will roll. 

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Last year I developed a pretty bad leak that was inconsistent, sometimes my system would stay charged overnight and sometimes it would loose enough air in 1/2 hour so that when I turn the key the low air alarm would come on.  I had checked the system early last year and it would stay up for days.   I actually cut a trip short and headed back home to work on it, glad I did.

First thing I did was make a set of ramps to lift the coach 6" so I could completely dump air.   This way I could safely work under the coach without having to worry about the air bags dropping etc.   I have jacks but did not want to rely on those.

I had sprayed down all the fittings on the tanks and found all the PPV's leaking some worse then others.  Ended up replacing all of them and some the check valves (tank to tank).  I did not have any leaks on my air dryer. 

My coach air will stay up for weeks now, both air bags and in the tanks.

 

Edited by jacwjames
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1 hour ago, rusty@kramermetalfab.com said:

Ok thanks for the replies. My goal is to locate an air leak and try to prevent idling the engine too much. The air connector does not sound to promising. 

I will just need to run the engine.

 

thanks

 

Run your engine at hi-idle. 1000+ RPM.

Only issue is it makes it near impossible to hear leaks anywhere near the engine. You will need to spray everything with soap and look for bubbles.

12 hours ago, Ivan K said:

Everything past and including dry tank will work as usual once you get enough pressure in. It will bypass the compressor, governor, drier and wet tank connections. Brake system, leveling will have air as usual.

I've always thought that connector feeds the wet tank.

*edit* What am I saying! I know it feeds the wet tank because mine doubles as my wet tank drain.

Edited by 96 EVO
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19 minutes ago, 96 EVO said:

Run your engine at hi-idle. 1000+ RPM.

Only issue is it makes it near impossible to hear leaks anywhere near the engine. You will need to spray everything with soap and look for bubbles.

I've always thought that connector feeds the wet tank.

*edit* What am I saying! I know it feeds the wet tank because mine doubles as my wet tank drain.

Certainly shows how different the implementations are from coach to coach. Yours would be safer to use but it still skips the dryer.  I feed mine with filtered dry air from paint room in my shop and use it often. BTW,  the park brake does not release just because there is air in the tanks, it still needs manual action. At least in my case...

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Ok Guys thanks. Went home for a bit and put the coach up on my ramps got everything ready and shut it down and found two fittings leaking. The plastic covers installed over the airline itself can make it difficult to detect with soap when the cover is right up to the fitting.  

I will replace these and see what I get.  I did not try to air it with the fitting I was just nervous about it. 

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Most of the fittings on my air lines were push to connect type.  If you have this type you can pull the airline out of the fitting, clean it, and push it back in and see if it seals.  It may not, you may have to cut ~1/2 of the old tubing off and see if you can get it to seal.

After working on mine I had several fitting that were hard to seal.  I had even replaced the fittings with new ones (kept the old as spares).  On one 1/2" push to connect fitting I could not get it to seal, one problem was that the tubing was coming in from at angle.  I finally just went and bought a compression fitting and that stopped the leak.  I think if I were to do it again I'd just use the compression type fittings, cheaper, readily available, and pretty much fool proof.

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1 hour ago, rusty@kramermetalfab.com said:

   I did not try to air it with the fitting I was just nervous about it. 

Your call!

The few times I've used my portable compressor to charge my tanks, I just let things sit for about an hour after without changing the air-leveling, or touching the brake system, then briefly cracked each of the tank drains. Never observed any moisture.

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21 hours ago, Larry Maida said:

Yes it will release the brakes. Is that your goal?? I would leave parking brake on (no air to braking system whick locks braked) Then run engine and look for leak. If you depress brake peddel and the pressure doesnt hold it is in braking system. Dont use the Tow Truck connection or your coach will roll. 

I think the tow truck connection just charges the air system as normal, so if the parking brake is set, it will remain set.

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Not sure about your system, but my air fill line in the front goes into the wet side of the front air tank.  I would think that for the minimal amount of air you may use the moisture would be minimal unless you were using the compressor during very high humidity conditions and a long time.  Anyway, if your set up is the same, you should be able to blowdown the wet tank afterwards.

Also just a thought, you may want to check your air ride levelers and fittings as well as the braking system.  Those can leak as well and not affect the coach level when parked.  I found most of my leaks at the swivel connections of the air fittings.  Replaced all those fittings with non-swivel connectors.

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If you haven't done it yet down load one of the files in the Air Systems sections of the download section.  I had one that I used when I worked on my coach, until I spend time working on it I really didn't understand how everything works.  After spending days working on my air system I'm pretty confident on how it works and how to track down problems.

One thing that was helpful was that the schematic show what color tubing was used for the different areas.  If the schematic said green tubing my rig had green tubing.  Right off hand I know there was red, green, blue, black, silver tubing (and others).  All the fittings and locations were the same as the schematics.  I did take pictures of everything as I was taking it apart to make sure all the pieces went back together they were suppose to.

Fortunately I wasn't in a hurry so I could remove a part and look for the best source for replacement.  I also found a local supplier of the fittings and tubing that had good prices.  I just took the fittings down there and got new ones.   

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2 hours ago, rusty@kramermetalfab.com said:

Thanks to all. I would agree that the crimp type would be better.  Most of mine are blowing out of the fitting where the hose is inserted. 20+ years and the o-ring seals show there age. 

Is it cold where you are?

Sometimes those press fit connections can leak a bit when it gets real cold, and seal back up as the temperature climbs!

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10 hours ago, dl_racing427 said:

I think the tow truck connection just charges the air system as normal, so if the parking brake is set, it will remain set.

The rear (parking) brake canisters should be caged if you do not want the parking brake to be activated.

Gary 05 AMB DST

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On 2/22/2022 at 10:43 AM, 96 EVO said:

Is it cold where you are?

Sometimes those press fit connections can leak a bit when it gets real cold, and seal back up as the temperature climbs!

It is cold outside but the coach is in a heated shop. Got the big leaks fixed still have others to search out.  Big Gas bubbles spray works well for checking leaks. Seems to cling better and last longer than soapy water mix I have tried. 

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Not sure what happen with my system but early last year I did a test to see how long my system would stay charged.  It went for almost a week with pressure high enough that my low air alarm would not come on with key on.

Then I took a trip and noticed that sitting overnight the air would drop quickly.  Sprayed down air connections and found all my PPV valves leaking and at one point when I stopped the pressure dropped within 30 minutes of stopping.  I cut my trip short and headed home to work on the problem. 

I replaced all the PPV valves and did replace all the check valves also since they are similar function.  When I pulled the old PPV I took them apart.  All of the springs and plates were extremely rusted.  The were all oriented in the wrong direction, the vent hole is suppose to be pointed down, all mine were pointed up (but this was the way the Monaco schematics showed).  I found installation instructions showing the right direction. 

 

PPV2.jpg

PPV correct orientation.jpg

PPV installation instructions.pdf

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  • 4 weeks later...

Don't forget the air connections to the parking brake button, tag axle regulator if you have one and the regulator for the step cover.  The air horn solenoid is one more place.   I have found leaks in some of these areas that tend to get overlooked.

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23 hours ago, granvillebarker said:

Don't forget the air connections to the parking brake button, tag axle regulator if you have one and the regulator for the step cover.  The air horn solenoid is one more place.   I have found leaks in some of these areas that tend to get overlooked.

Yeah, my rig had a fairly large leak last fall when I got it would lose air overnight. The step cover also wouldn't retract reliably so I pulled the step cover valve that mounts in the front bay (with the generator out) and sure enough the housing was cracked. Replace it with a new one and now holds air perfectly overnight. The step  cover works great too, maybe a little too aggressive worried about cutting my dog in half! I think there might be adjustment screws on the valve I'll have to investigate to see if I can dial it back a bit.

641714011_ScreenShot2022-03-23at8_49_38AM.png.280ba8b62ff6006c381860120a0f7429.png

Edited by RoadTripper2084
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On 2/20/2022 at 11:40 PM, rustykramermetalfab said:

Hello Group.

 If I connect compressed air to the air connector up front for the tow truck brake release, does this charge the chassis air system just as if the engine is running?

I have a massive air leak that has developed as the coach has been sitting. I need to diagnose and need to keep the system charged without running the engine if this is possible?

2000 Dynasty HWH leveling system. The air bags stay up for months so the leak must be in the brake system?

Thanks.

 

You could buy a air dryer filter for your compressor.

Gary 05 AMB DST

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