Air loss exiting highway.

[Brian J]

I had a large opportunity present itself on a current trip from California to Las Vegas.

I have a 05 Monaco Dynasty, ISL 400, Allison 3000.

When I exited the highway and was heading to Las Vegas Motorcoach resort. The low air pressure alarm sounded and I was losing rear tank pressure fast. I was able to limp into my site, having to stop and try and get pressure up, emergency brake was trying to engage. 

After some investigation utilizing a small compressor and a go pro I was able to find the leak/s. The yellow and orange lines have wear holes where it's been rubbing against some frame work, just under the rear bedroom hatch to the engine. Of coarse tucked back in an area impossible to reach to splice.

I have pictures to attach.

From what I can tell utilizing the 05 Monaco airline schematic and hands on tracing these lines under coach, I should be able to cut the lines before the leak and run new lines splicing back in along side the motor. These areas I can access without a lot of trouble.

My question is does this look as an acceptable fix or am I missing something in the schematic and with my looking at the actual airlines.

I appreciate any and all help.

Brian Jones

[dennis.mcdonaugh]

Running a new air line shouldn’t be an issue. All the air lines on my coach run through corrugated plastic conduit. It doesn’t look like yours does. 

Edited December 28, 2023 by dennis.mcdonaugh

[Frank McElroy]

On 12/27/2023 at 10:22 PM, Brian J said:

I had a large opportunity present itself on a current trip from California to Las Vegas.

I have a 05 Monaco Dynasty, ISL 400, Allison 3000.

When I exited the highway and was heading to Las Vegas Motorcoach resort. The low air pressure alarm sounded and I was losing rear tank pressure fast. I was able to limp into my site, having to stop and try and get pressure up, emergency brake was trying to engage. 

After some investigation utilizing a small compressor and a go pro I was able to find the leak/s. The yellow and orange lines have wear holes where it's been rubbing against some frame work, just under the rear bedroom hatch to the engine. Of coarse tucked back in an area impossible to reach to splice.

I have pictures to attach.

From what I can tell utilizing the 05 Monaco airline schematic and hands on tracing these lines under coach, I should be able to cut the lines before the leak and run new lines splicing back in along side the motor. These areas I can access without a lot of trouble.

My question is does this look as an acceptable fix or am I missing something in the schematic and with my looking at the actual airlines.

I appreciate any and all help.

Brian Jones

Doing the repair as you described is fine.

However you should do a check of the braking system after the repair.  Air up the system until the air compressor governor cuts out.  With the engine running, wheels chocked, and parking brake released, dump all air from the front wet air tank (drain valve with the male quick connect fitting) and rear main dry air tank. 

After doing that, you should have at least about 8 full brake applications using air from the front secondary air tank before the parking brake actuates.  (On my coach, I get 13 full brake applications before the parking brake automatically popped up.)  With the rear air tank empty, steer axle braking will be from the front secondary tank (same as if the main air tank was working).  Braking on the drive axle (your main braking axle) will be by the system modulating the parking brake release spring.  There are modules that automatically do that for you.  There will be no braking on the tag axle. 

While doing this test, if someone looks from the side of the coach, they should see the drive axle brakes being activated.  That's a good way to check that the parking brake modulating system is working should there be a failure of the rear main air tank.

Just to complete the story, if you air up the system and this time dump the wet and front secondary tanks, the rear main tank should have at least about 8 full brake applications of the drive and tag axles before the parking brake pops up.  (I get 12 full brake applications).  With the secondary air tank empty there would be no braking on the steer axle.

The system is designed such that in the event of a failure either the Primary or Secondary system you have enough braking applications to safely exit the highway and stop in a safe location vs just immediately pulling onto the shoulder of a busy highway.

[Brian J]

Thanks for the info, I did the bypass successfully.

The emergency/parking brake was popping up as I was driving through RV park, had to stop and run up rpms to get air pressure up.

I did notice a solenoid valve has a small leak from the bottom, I believe this to be the MAC valve referenced in the schematic.

From what I can decipher this is to lift the tag axle.

Has the valve gone bad? It's a very low volume leak.

Pic attached, this is inside rear engine hatch on left side.

 

I will be doing the brake test before leaving for home.

 

[Frank McElroy]

It is very common for this tag axle regulator to leak air and when it does it will need to be replaced. 

Below is a more detailed air brake system test that you should perform periodically.  

 

[Brian J]

Thanks for the invaluable help!!

 

Brian