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deandec · 10-05-2019, 07:57 PM

This is a new situation for us!

Rig is parked with house battery shut off so the little electric leveling air compressor does not operate.

Both the Primary and Secondary Reservoirs Leak down to empty in less than 24 hours. Actually dropped to 30 psi after eight hours.

The rig passed the DOT Pre-Trip air brake test procedure with nary a hiccup.

The automatic air drains function properly and shed no water in our low humidity climate.

The air leveling system maintains ride height level for well more than 24 hours.

The air throttle works once the compressor restores air to the accessory tank at startup.

The only new event is the air tanks not retaining air! (This includes the accessory reservoirs for Air Throttle and Leveling.)

It appears the Compressor, Governor, and Air Filter are working as designed as 120 psi air pressure is restored reasonably quickly at engine start.

I can detect no leak by sound.

I would guess the leak must be very slow and somewhere between the the air lines into the air tanks and the dash air gauge?

Does anyone have experience or recommendations with this type of event?

BrianGlenn · 10-05-2019, 08:30 PM

You have covered off the major troubleshooting items. Now it requires detailed leak testing at fitting connections in the pneumatic brake systems and the leveling system.

Getting under the coach and testing fittings is a difficult, labor intensive task.

pumper9x9 · 10-06-2019, 08:42 AM

If your air dryer has failed it will send desiccant powder all through your air system and may be gumming up the works.

deandec · 10-06-2019, 09:56 AM

Quote:

Originally Posted by pumper9x9

If your air dryer has failed it will send desiccant powder all through your air system and may be gumming up the works.

What are the symptoms of the Air dryer failing?

TR4 · 10-06-2019, 10:22 AM

Use dishwashing liquid in a spray bottle, spray all lines and fittings. I found my leaks at the pressure gauge and low air pressure switch. You won’t be able to hear small leaks.

It’s strange that both primary and secondary tanks are loosing pressure since the have check valves. I’d look at the pressure gauge behind the dash, they have both lines connected. Sounds like you have more than one leak.

Bill

deandec · 10-06-2019, 02:15 PM

Thanks for the specific pointers. I guess I will start behind the dash as that is easiest to get to then go under with my bottle of soap.

Most likely on Monday.

BonS · 10-06-2019, 03:00 PM

I've been having a very similar problem. The diagnosis for my coach is a bad check valve and a leaky pressure relief valve. The parts are in and I hope to have those replaced tomorrow. Fingers crossed.

Roy1 · 10-06-2019, 06:23 PM

My neighbor is a retired diesel mechanic he said when he worked at LAX they would add a small amount of refrigerant too the air systems too locate small leaks and leak check with an a/c leak detector. Never tried it but it would be an easy way to leak check if it worked.

pumper9x9 · 10-07-2019, 09:26 AM

Quote:

Originally Posted by deandec

What are the symptoms of the Air dryer failing?

Look for powder residue around automatic bleeders and around the cans for the sir brakes. It's recommended you replace them about every 2 yrs. I was ignorant that they even existed.

deandec · 10-07-2019, 09:44 AM

Ok, thanks I will take a look while under there.

CC put ours in such a difficult place to access.

deandec · 10-07-2019, 01:36 PM

Quote:

Originally Posted by deandec

Thanks for the specific pointers. I guess I will start behind the dash as that is easiest to get to then go under with my bottle of soap.

Most likely on Monday.

Well not today for checking the system from down under.

I did spray soapy water and touch the connections in the front basement compartment, below the front bumper, at the dash and in the engine compartment. I could not hear, feel or see any air escaping today from those connections.

So I will have to get to the air bags, brake pods, air tanks and air dryer another day.

deandec · 10-07-2019, 01:39 PM

Quote:

Originally Posted by BonS

I've been having a very similar problem. The diagnosis for my coach is a bad check valve and a leaky pressure relief valve. The parts are in and I hope to have those replaced tomorrow. Fingers crossed.

Did they tell you which check valve and pressure relief valve they are replacing?

Hope they achieve success.

BonS · 10-07-2019, 07:10 PM

Quote:

Originally Posted by deandec

Did they tell you which check valve and pressure relief valve they are replacing?

Hope they achieve success.

No, but they did it today. I'll have to wait 24-48 hours before I'll know if they were successful. I'm going back next Monday for other work and I'll press them to ID it. I have a pneumatic schematic and they might be able to point to it. I can call them sooner if you think it would help.

Spk64 · 10-07-2019, 07:26 PM

When I had a leak it was a check valve and pressure protection valve that fixed most of it. Soapy water showed them leaking badly.
Also had replaced a rear ride height valve that was also leaking the year before.
This is on a Spartan chassis but same principles on the CC.
Check valve and Pressure Protection valve were at the tanks.