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Old 04-06-2020, 08:03 PM   #1
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How do I service my air system?

I have a 2007 Winnebago Journey 34H on a Freightliner chassis.


I have read various threads, here, relating to the air system. I have looked for, but not found, a simple bulleted list of what I should do periodically to check and maintain my air system. I am pretty mechanically inclined but know nothing about the pneumatic system on an RV. According to my dash air gauges, I loose much the pressure in my system within 30 minutes. Using soapy spray, I did find one connection leaking a bit, but I am not even sure what I should be checking.



What things should do I do or check? Where are those "things" located under the coach?


What, if anything, should be replaced periodically? Where are those "things" located under the coach?


Thank you for your time.
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Old 04-06-2020, 08:11 PM   #2
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Run it through this series of tests first. Then you’ll know what you need to address. Pretty much the point of daily, weekly, and monthly checks.

5.1 – Parts of an Air Brake System

5.2 – Dual Air Brake

5.3 – Inspecting Air Brake Systems

5.4 – Using Air Brakes

Air brakes use compressed air to make the brakes work. Air brakes are a good and safe way of stopping large and heavy vehicles, but the brakes must be well maintained and used properly.

Air brakes are really 3 different braking systems: service brake, parking brake, and emergency brake.

The service brake system applies and releases the brakes when you use the brake pedal during normal driving.
The parking brake system applies and releases the parking brakes when you use the parking brake control.
The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure.
CDL Air Brake Requirements. For CDL purposes, a vehicle’s air brake system must meet the above definition and contain the following, which will be checked during the vehicle inspection test:

Air gauges.
Low pressure warning device(s).
If the vehicle you use for your driving test does not have these components, your vehicle will not be considered as having an air brake system and you will have a “No Air Brakes” restriction on your CDL.

Note: A full service brake application must deliver to all brake chambers not less than 90 percent of the air reservoir pressure remaining with the brakes applied (CVC 26502).

The parts of these systems are discussed in greater detail in the following paragraphs.

5.1 – Parts of an Air Brake System

There are many parts to an air brake system. You should know about the parts discussed here.

5.1.1 – Air Compressor

The air compressor pumps air into the air storage tanks (reservoirs). The air compressor is connected to the engine through gears or a v-belt. The compressor may be air cooled or cooled by the engine cooling system. It may have its own oil supply or be lubricated by engine oil. If the compressor has its own oil supply, check the oil level before driving.

5.1.2 – Air Compressor Governor

The governor controls when the air compressor will pump air into the air storage tanks. When air tank pressure rises to the “cut-out” level (around 125 pounds per-square-inch or “psi”), the governor stops the compressor from pumping air. When the tank pressure falls to the “cut-in” pressure (around 100 psi), the governor allows the compressor to start pumping again.

5.1.3 – Air Storage Tanks

Air storage tanks are used to hold compressed air. The number and size of air tanks varies among vehicles. The tanks will hold enough air to allow the brakes to be used several times, even if the compressor stops working.

5.1.4 – Air Tank Drains

Compressed air usually has some water and some compressor oil in it, which is bad for the air brake system. For example, the water can freeze in cold weather and cause brake failure. The water and oil tend to collect in the bottom of the air tank. Be sure that you drain the air tanks completely. Each air tank is equipped with a drain valve in the bottom. There are 2 types:

Manually—operated by turning a quarter turn or pulling a cable. You must drain the tanks yourself at the end of each day of driving.
Automatic—the water and oil are automatically expelled. These tanks may be equipped for manual draining as well.
Automatic air tanks are available with electric heating devices. These help prevent freezing of the automatic drain in cold weather.


5.1.5 – Alcohol Evaporator

Some air brake systems have an alcohol evaporator to put alcohol into the air system. This helps to reduce the risk of ice in air brake valves and other parts during cold weather. Ice inside the system can make the brakes stop working.

Check the alcohol container and fill up as necessary. (every day during cold weather). Daily air tank drainage is still needed to get rid of water and oil (unless the system has automatic drain valves).

5.1.6 – Safety Valve

A safety relief valve is installed in the first tank the air compressor pumps air to. The safety valve protects the tank and the rest of the system from too much pressure. The valve is usually set to open at 150 psi. If the safety valve releases air, something is wrong. Have the fault fixed by a mechanic.

5.1.7 – The Brake Pedal

You engage the brakes by pushing down the brake pedal (It is also called a foot valve or treadle valve). Pushing the pedal down harder applies more air pressure. Letting up on the brake pedal reduces the air pressure and releases the brakes. Releasing the brakes lets some compressed air go out of the system, so the air pressure in the tanks is reduced. It must be made up by the air compressor. Pressing and releasing the pedal unnecessarily can let air out faster than the compressor can replace it. If the pressure gets too low, the brakes will not work.

5.1.8 – Foundation Brakes

Foundation brakes are used at each wheel. The most common type is the S-cam drum brake. The parts of the brake are discussed below.

Brake Drums, Shoes, and Linings. Brake drums are located on each end of the vehicle’s axles. The wheels are bolted to the drums. The braking mechanism is inside the drum. To stop, the brake shoes and linings are pushed against the inside of the drum. This causes friction, which slows the vehicle (and creates heat). The heat a drum can take without damage depends on how hard and how long the brakes are used. Too much heat can make the brakes stop working.

S-cam Brakes. When you push the brake pedal, air is let into each brake chamber. Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake camshaft. This turns the S-cam (it is shaped like the letter “S”). The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. When you release the brake pedal, the S-cam rotates back and a spring pulls the brake shoes away from the drum, letting the wheels roll freely again. See Figure 5.2.

CamLaster. The CamLaster brake has 2 key design differences over traditional S-cam brakes.

One feature is a completely internal adjustment system which is designed to continually keep the brake in proper adjustment. S-cam brakes, on the other hand, require an external slack adjuster. The second feature is a unique cam design that applies the brake shoe. Unlike a standard drum brake that has either a single or double anchor-pin brake, the CamLaster slides the shoes down an inclined ramp on a cam to evenly contact the brake drum.

Wedge Brakes. In this type of brake, the brake chamber push rod pushes a wedge directly between the ends of 2 brake shoes. This shoves them apart and against the inside of the brake drum. Wedge brakes may have a single brake chamber, or 2 brake chambers, pushing wedges in at both ends of the brake shoes. Wedge type brakes may be self-adjusting or may require manual adjustment.

Disc Brakes. In air-operated disc brakes, air pressure acts on a brake chamber and slack adjuster, like S-cam brakes. But instead of the S-cam, a “power screw” is used. The pressure of the brake chamber on the slack adjuster turns the power screw. The power screw clamps the disc or rotor between the brake lining pads of a caliper, similar to a large c-clamp.

Wedge brakes and disc brakes are less common than S-cam brakes.

5.1.9 – Supply Pressure Gauges

All vehicles with air brakes have a pressure gauge connected to the air tank. If the vehicle has a dual air brake system, there will be a gauge for each half of the system (or a single gauge with two needles). Dual systems will be discussed later. These gauges tell you how much pressure is in the air tanks.

5.1.10 – Application Pressure Gauge

This gauge shows how much air pressure you are applying to the brakes. (This gauge is not on all vehicles.) Increasing application pressure to hold the same speed means the brakes are fading. You should slow down and use a lower gear. The need for increased pressure can also be caused by brakes being out of adjustment, air leaks, or mechanical problems.

5.1.11 – Low Air Pressure Warning

A low air pressure warning signal is required on vehicles with air brakes. A warning signal you can see must come on when the air pressure in the tanks falls between 55 and 75 psi (or 1/2 the compressor governor cutout pressure on older vehicles). The warning is usually a red light. A buzzer may also come on.

Another type of warning is the “wig wag.” This device drops a mechanical arm into your view when the pressure in the system drops between 55 and 75 psi. An automatic wig wag will rise out of your view when the pressure in the system goes above 55 and 75 psi. The manual reset type must be placed in the “out of view” position manually. It will not stay in place until the pressure in the system is above 55 psi.

On large buses, it is common for the low pressure warning devices to signal at 80–85 psi.

5.1.12 – Stop Light Switch

Drivers behind you must be warned when you put your brakes on. The air brake system does this with an electric switch that works by air pressure. The switch turns on the brake lights when you put on the air brakes.

5.1.13 – Front Brake Limiting Valve

Some older vehicles (made before 1975) have a front brake limiting valve and a control in the cab. The control is usually marked “normal” and “slippery.” When you put the control in the “slippery” position, the limiting valve cuts the “normal” air pressure to the front brakes by half. Limiting valves were used to reduce the chance of the front wheels skidding on slippery surfaces. However, they actually reduce the stopping power of the vehicle. Front wheel braking is good under all conditions. Tests have shown front wheel skids from braking are not likely even on ice. Make sure the control is in the “normal” position to have normal stopping power.

Many vehicles have automatic front wheel limiting valves. They reduce the air to the front brakes except when the brakes are put on very hard (60 psi or more application pressure). These valves cannot be controlled by the driver.

5.1.14 – Spring Brakes

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. They must be held on by mechanical force (because air pressure can eventually leak away). Spring brakes are usually used to meet these needs. Powerful springs are held back by air pressure, when driving. If the air pressure is removed, the springs put on the brakes. A parking brake control in the cab allows the driver to let the air out of the spring brakes. This lets the springs put the brakes on. A leak in the air brake system, which causes all the air to be lost, will also cause the springs to put on the brakes.

Tractor and straight truck spring brakes will come fully on when air pressure drops to a range of 20 to 45 psi (typically 20 to 30 psi). Do not wait for the brakes to come on automatically. When the low air pressure warning light, and buzzer first come on, bring the vehicle to a safe stop right away, while you can still control the brakes.

The braking power of spring brakes depends on the brakes being in adjustment. If the brakes are not adjusted properly, neither the regular brakes nor the emergency/parking brakes will work right.

5.1.15 – Parking Brake Controls

In newer vehicles with air brakes, you put on the parking brakes using a diamond-shaped, yellow, push-pull control knob. You pull the knob out to put the parking brakes (spring brakes) on, and push it in to release them. On older vehicles, the parking brakes may be controlled by a lever. Use the parking brakes whenever you park.

Caution. Never push the brake pedal down when the spring brakes are on. If you do, the brakes could be damaged by the combined forces of the springs and the air pressure. Many brake systems are designed so this will not happen. Not all systems are set up that way, and those that are may not always work. It is much better to develop the habit of not pushing the brake pedal down when the spring brakes are on.

Modulating Control Valves. In some vehicles a control handle on the dash board may be used to apply the spring brakes gradually. This is called a modulating valve. It is spring-loaded so you have a feel for the braking action. The more you move the control lever, the harder the spring brakes come on. They work this way so you can control the spring brakes if the service brakes fail. When parking a vehicle with a modulating control valve, move the lever as far as it will go and hold it in place with the locking device.

Dual Parking Control Valves. When main air pressure is lost, the spring brakes come on. Some vehicles, such as buses, have a separate air tank which can be used to release the spring brakes. This is so you can move the vehicle in an emergency. One of the valves is a push-pull type and is used to put on the spring brakes for parking. The other valve is spring loaded in the “out” position. When you push the control in, air from the separate air tank releases the spring brakes so you can move. When you release the button, the spring brakes come on again. There is only enough air in the separate tank to do this a few times. Therefore, plan carefully when moving. Otherwise, you may be stopped in a dangerous location when the separate air supply runs out.

5.1.16 – Antilock Braking Systems

Truck tractors with air brakes built on or after March 1, 1997, and other air brakes vehicles, (trucks, buses, trailers, and converter dollies) built on or after March 1, 1998, are required to be equipped with antilock brakes. Many commercial vehicles built before these dates have been voluntarily equipped with ABS. Check the certification label for the date of manufacture to determine if your vehicle is equipped with ABS. ABS is a computerized system that keeps your wheels from locking up during hard brake applications.

Vehicles with ABS have yellow malfunction lamps to tell you if something is not working.
Tractors, trucks, and buses will have yellow ABS malfunction lamps on the instrument panel.
Trailers will have yellow ABS malfunction lamps on the left side, either on the front or rear corner. Dollies manufactured on or after March 1, 1998 are required to have a lamp on the left side.
On newer vehicles, the malfunction lamp comes on at start-up for a bulb check, and then goes out quickly. On older systems, the lamp could stay on until you are driving over 5 mph.

If the lamp stays on after the bulb check, or goes on once you are under way, you may have lost ABS control at one or more wheels.
In the case of towed units manufactured before it was required by the DOT, it may be difficult to tell if the unit is equipped with ABS. Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.
ABS is an addition to your normal brakes. It does not decrease or increase your normal braking capability. ABS only activates when wheels are about to lock up.
ABS does not necessarily shorten your stopping distance, but it does help you keep the vehicle under control during hard braking.

5.2 – Dual Air Brake

Most heavy-duty vehicles use dual air brake systems for safety. A dual air brake system has 2 separate air brake systems, which use a single set of brake controls. Each system has its own air tanks, hoses, lines, etc. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle (and possibly one rear axle). Both systems supply air to the trailer (if there is one). The first system is called the “primary” system. The other is called the “secondary” system.

Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum of 100 psi pressure in both the primary and secondary systems. Watch the primary and secondary air pressure gauges (or needles, if the system has 2 needles in one gauge). Pay attention to the low air pressure warning light and buzzer. The warning light and buzzer should shut off when air pressure in both systems rises to a value set by the manufacturer. This value must be greater than 55 psi.

The warning light and buzzer should come on before the air pressure drops below 55 psi in either system. If this happens while driving, you should stop right away and safely park the vehicle. If one air system is very low on pressure, either the front or the rear brakes will not be operating fully. This means it will take you longer to stop. Bring the vehicle to a safe stop, and have the air brakes system fixed.

One-Way Check Valve

This device allows air to flow in one direction only. All air tanks on air-braked vehicles must have a check valve located between the air compressor and the first reservoir (CVC 26507). The check valve keeps air from going out if the air compressor develops a leak.

5.3 – Inspecting Air Brake Systems

You should use the basic 7-step inspection procedure described in Section 2 to inspect your vehicle. There is more to inspect on a vehicle with air brakes than one without them. These components are discussed below, in the order that they fit into the 7-step method.

5.3.1 – During Step 2 Engine Compartment Checks

Check air compressor drive belt (if compressor is belt-driven). If the air compressor is belt-driven, check the condition and tightness of the belt. It should be in good condition.

5.3.2 – During Step 5 Walk Around Inspection

Check slack adjusters on S-cam brakes. Park on level ground and chock the wheels to prevent the vehicle from moving. Release the parking brakes so you can move the slack adjusters. Use gloves and pull hard on each slack adjuster that you can reach. If a slack adjuster moves more than about one inch where the push rod attaches to it, it probably needs adjustment. Adjust it or have it adjusted. Vehicles with too much brake slack can be very hard to stop. Out-of-adjustment brakes are the most common problem found in roadside inspections. Be safe. Check the slack adjusters.

All vehicles built since 1994 have automatic slack adjustors. Even though automatic slack adjustors adjust themselves during full brake applications, they must be checked.

Automatic adjusters should not have to be manually adjusted except when performing maintenance on the brakes and during installation of the slack adjusters. In a vehicle equipped with automatic adjusters, when the pushrod stroke exceeds the legal brake adjustment limit, it is an indication that a mechanical problem exists in the adjuster itself, a problem with the related foundation brake components, or that the adjuster was improperly installed.

The manual adjustment of an automatic adjuster to bring a brake pushrod stroke within legal limits is generally masking a mechanical problem and is not fixing it. Further, routine adjustment of most automatic adjusters will likely result in premature wear of the adjuster itself. It is recommended that when brakes equipped with automatic adjusters are found to be out of adjustment, the driver take the vehicle to a repair facility as soon as possible to have the problem corrected. The manual adjustment of automatic slack adjusters is dangerous because it may give the driver a false sense of security regarding the effectiveness of the braking system.

The manual adjustment of an automatic adjuster should only be used as a temporary measure to correct the adjustment in an emergency situation as it is likely the brake will soon be back out of adjustment since this procedure usually does not fix the underlying adjustment problem.

Note: Automatic slack adjusters are made by different manufacturers and do not all operate the same. Therefore, the specific manufacturer’s service manual should be consulted prior to troubleshooting a brake adjustment problem.

Check Brake Drums (or Discs), Linings, and Hoses

Brake drums (or discs) must not have cracks longer than 1/2 the width of the friction area. Linings (friction material) must not be loose or soaked with oil or grease and must not be worn dangerously thin (less than 1/4 inch). Mechanical parts must be in place, not broken or missing. Check the air hoses connected to the brake chambers to make sure they are not cut or worn due to rubbing.

5.3.3 – Step 7 Final Air Brake Check

Note: All the air brakes system tests in this section are considered important and each can be considered critical parts of the in-cab air brakes tests. The items marked with an asterisk (*) in this section are required for testing purposes during the vehicle inspection portion of the CDL skills test. They may be performed in any order as long as they are performed correctly and effectively. If these items are not demonstrated and the parameters for each test are not verbalized correctly, it is considered an automatic failure of the vehicle inspection portion of the skills test.

Do the following checks instead of the hydraulic brake check shown in Section 2, Step 7: Check Brake System.

*Test Low Pressure Warning Signal

To perform this test, the vehicle must have enough air pressure so the low pressure warning signal is off. The engine may be on or off; however, the key must be in the “on” or “battery charge” position. Next, begin fanning off the air pressure by rapidly applying and releasing the foot brake. The low pressure warning signal (buzzer, light, or flag) will generally activate when the air pressure falls between 55–75 psi, but may activate at a higher pressure (80–85 psi) if specified by the manufacturer. The low air pressure warning signal must activate before the air supply pressure drops below 55 psi in the air tank (or tank with the lowest air pressure in dual air systems). The vehicle is not safe to operate if the low air warning signal does not activate before the air supply pressure drops below 55 psi.

For testing purposes, identify and verbalize the pressure at which the low air pressure warning signal activates and identify the parameter(s) at which this should occur. On large buses, it is common for the low pressure warning devices to signal at 80–85 psi. On large buses, it is common for the low pressure warning devices to signal at 80–85 psi. If testing in a large bus, identify the parameter(s) mentioned above (55–75 psi) and inform the examiner that your vehicle’s low pressure warning devices are designed to activate at a higher pressure.

If the warning signal does not work, you could lose air pressure and not know it. This could cause sudden emergency braking in a single-circuit air system. In dual systems, the stopping distance will be increased. Only limited braking can be done before the spring brakes come on.

Note: Farm labor vehicles and Type I school buses must be equipped with both an audible and visible type warning device.

*Check That Spring Brakes Come on Automatically

Chock the wheels. Release the parking brake valve (all vehicles) and the tractor protection valve (combination vehicles) and begin reducing the air pressure by stepping on and off the brake pedal. Then the air tank pressure has fallen between 20 and 45 psi on a tractor-trailer combination vehicle, the tractor protection valve and parking brake valve should close (pop out). On other combination vehicle types and single vehicle types, the parking brake valve should pop out. For testing purposes, identify and verbalize the approximate pressure at which the brakes activate and the parameters at which this would occur.

Note: The parking brake valve will not pop out on buses that are equipped with an emergency park brake air reservoir (tank). If your bus is equipped with an emergency park brake air tank, you must perform the spring brake test for triple reservoir vehicles to check the automatic actuation of the spring brakes.

Spring Brake Test for Triple Reservoir Vehicles

If the parking brake valve does not pop out when the air pressure has been reduced to approximately 20 psi, you must demonstrate that the spring brakes have activated. To do this, you must:

Remove the wheel chocks, if necessary.
Leave the parking brake valve in the open (released) position.
With the engine running, put the vehicle in a forward gear and attempt to drive forward.
The spring brakes should drag and prevent the vehicle from easily moving forward. If the spring brakes do not prevent the vehicle from easily moving forward, your driving test will be postponed.

Note: This test must only be performed on single vehicles designed with an isolated parking brake reservoir. Do not perform this test on combination vehicles.

Check Rate of Air Pressure Buildup

To perform this test, the engine must be running at normal operating idle, typically 600–900 rpms. Observe the air gauge to determine if the pressure builds at the proper rate. For dual air systems, the pressure should build from approximately 85 to 100 psi within 45 seconds. For single air systems (pre-1975), the pressure should build from approximately 50 to 90 psi within 3 minutes.

Test Air Leakage Rate

There are 2 tests as follows:

Static Leakage Test

With a basically fully-charged air system (within the effective operating range for the compressor), turn off the engine, release all brakes, and let the system settle (air gauge needle stops moving). Time for one minute. The air pressure should not drop more than:

2 psi for single vehicles.
3 psi for a combination of 2 vehicles.
5 psi for a combination of 3 or more vehicles.
Important: The maximum air loss rate for a combination of 2 or more vehicles is 2 psi if the towed vehicles are not equipped with air brakes.
An air loss greater than those shown above indicate a problem in the braking system and repairs are needed before operating the vehicle.

*Applied Leakage Test

To perform this test, the vehicle’s air pressure should be built up to maximum pressure (cut-out). With the air pressure built up, shut off the engine, chock the wheels if necessary, release the parking brake (all vehicles) and the tractor protection valve (combination vehicle), and firmly apply the foot brake. Then hold the foot brake for 1 minute after stabilization of the air gauge. Check the air gauge to see that the air pressure drops no more than 3 psi in 1 minute (single vehicle) or 4 psi in 1 minute (combination vehicle) and listen for air leaks. You must identify how much air the system lost and verbalize the maximum air loss rate allowed for your vehicle.

3 psi for single vehicles.
4 psi for a combination of 2 vehicles.
6 psi for a combination of 3 or more vehicles.
Important: The maximum air loss rate for a combination of 2 or more vehicles is 3 psi if the towed vehicles are not equipped with air brakes.
An air loss greater than those listed above indicates a problem in the braking system and repairs are needed before operating the vehicle.

If the air loss is too much, check for air leaks and fix any that are identified. For testing purposes, identify if the air loss rate is too much.

*Air Compressor Governor Cut-Out Pressure Test

To perform this test, the air pressure for the vehicle must be rising when the engine is running. Governor cut-out occurs when the needle stops rising. The air compressor should cut-out not higher than 140 psi (max).

Note: The air dryer exhausting should not be referenced as governor cut-out

*Air Compressor Governor Cut-In Pressure Test

To perform this test, the air pressure for the vehicle cannot be rising when the engine is running. With the air pressure at maximum pressure (cut-out), begin slowly pumping the brake pedal to reduce the air tank pressure. Watch the air pressure gauge between pumps to identify when the compressor cuts in (needle starts to rise). This must occur no lower than 85 psi for a bus, and no lower than 100 psi for trucks.

Test Parking Brake

Fasten your seat belt. Set the parking brake, and gently pull against it in a low gear to test that the parking brake will hold.

Test Service Brakes

Wait for normal air pressure, release the parking brake, move the vehicle forward slowly (about 5 mph), and apply the brakes firmly using the brake pedal. Note any vehicle “pulling” to one side, unusual feel, or delayed stopping action.

This test may show you problems, which you otherwise would not know about until you needed the brakes on the road.
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Old 04-06-2020, 08:23 PM   #3
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There’s a bunch more info on the subject from lots of users here:

https://www.irv2.com/forums/f258/air...ng-480401.html

Might be good to just read through the whole thing and see what you pick up.

And then I just saw this a few minutes ago. Very good bit of info to keep in mind:

https://www.irv2.com/forums/f278/air...or-484026.html
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Old 04-07-2020, 11:03 AM   #4
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Contact Freightliner's free help line with your chassis serial number, and ask for an air system diagram for your chassis. That diagram will give you an indication of all the parts involved in the air system in your coach.

Questions like yours , are the main reason that many states now require training and testing on air brake systems by all drivers operating vehicles equipped with the system.

Regular draining of the air system tanks and maintenance of the air dryer , checking the operation of the auto slack adjusters and proper lubrication of the " S " cam activation shaft are all important to the continued proper operation of the brakes on your coach.

Your 30 min. pressure leak down is a MAJOR concern , I'd say anything under three days a problem.
If I don't bleed my system down by dumping the air suspension , the tanks will be at 100 psi+ for a week or more.

1-800-FTL-HELP
1-800-385-4357

Do a Google search for a " Bendix Air Brake Handbook " for pictures and identification of all brake system parts. I have the pdf but it's too large a file to post here in the forums.
Attached Files
File Type: pdf Air brake testing.pdf (439.4 KB, 21 views)
File Type: pdf Air Dryer Maintenance web version.pdf (161.5 KB, 21 views)
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Old 04-07-2020, 12:27 PM   #5
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Thank you for the responses, above.
It will take me a while to digest all of this information. The information, above, seems to focus on the brakes, and does not address the suspension. Any additional information on the suspension?
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Old 04-07-2020, 12:28 PM   #6
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dmevis,

I used to have the '07 Meridian 34H and loved it. Stepped up to a 2011 Ellipse 42Q - only 6' longer but it sure looks bigger.

Your manual will give you a basic overview of the system and general location of each item: i.e. air tanks; wastegate; airbags; air dryer (which has a filter that needs to be replaced every 2 years); etc.

After the manual I started watching videos online and reading every post I could making notes as I went along.

With a 30" depletion time it appears you have a leak somewhere. My Meridian would stay inflated for several days if I didn't manually dump. With my current DP I manually dump when I'm going to be setting still for extended period of time - helps getting in and out as it settles about 6". If I use my jacks it automatically dumps prior to extending the jacks.

Recommend getting under DP starting at the front tire. Locate the air bag and follow the hoses down to the tank checking each connection for leaks as you go. From the tank follow lines to the and from the air compressor, the secondary tanks and to the back of the rig to the air dryer. It is easy to locate when you have aired up the lines with DP at ride height because you will hear it expel air with a pop and hiss about every 20 to 30 seconds - this is normal.

It's not as difficult to learn as it may appear. Just take your time and if you run into a problem take a picture and bring it and your problem back to the site for wisdom beyond mine. These guys are gracious and generous.

Be Safe - Stay Safe and Drive ON - Richard
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Old 04-07-2020, 01:58 PM   #7
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You have a 2007 coach. Do you know if the air system "filter"has ever been changed? It should be done every 3 years +_ or so.

You do have a significant air leak somewhere and I implore you to get it looked at. That leak can be anywhere from the filter back on the drivers side frame right behind the rear wheels, to the air tanks and beyond. I found several leaks in my 2006 coach when I was checking. The largest by far was the drain valve on one of the tanks. When I pulled the lanyards to expel a small amount of water illuminated in the tanks the valve did not seat properly. After pulling on the lanyards several time afterwards, the valve finally resealed itself.

Good luck and keep us informed as to what you find.
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Old 04-07-2020, 08:33 PM   #8
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let me give you a less technical response. When it comes to the air system. Lets start with the brakes there is a pre trip brake test that you should do before you depart. I don't always do it but you should. There are videos on line that walk you through the test. air up the system and hold the brake for 60 seconds you should not lose more that 3 to 5 lbs of air at full application. Then you turn off the motor press and release brakes to deplete the air in the system and make sure the emergency brake deploys. I like to monitor how frequently that system recharges itself as i am traveling down the road with no brake application. I can go about 25 to 30 min., between cycles.

All of the above is to make sure that you don't have any serious issues with the air lines in the brake system.

Its always a good idea to get under there with a spray bottle looking for leaks in the lines, relays, chambers, bags and holding tanks.
As someone said need to replace the air dryer filter at least every three years or less.

I recently found a leak in my rear spring brake chamber. With the coach aired up. power off, wheels chalked, you take off the emergency brake. that compresses air in the rear spring brake chambers, if you hear air leaking or see a loss of pressure you have an issue.

You check the service side of the brake chambers by having someone take off the parking brake and apply the service brakes, again with the wheels blocked, get under there to listen for air escaping from the brake chambers.

On the air bags you want to inspect for visible damage and use soap water to detect leaks. They generally will leak at the bottom of the bag and/or the top air connections.

lastly the coach has leveling valves that adjust the ride height of the coach as your driving down the road. you should check them for leaks and while your at it you should check that they are adjusted correctly.

You can call FL with your vin number they will give you the ride height of your chassis. the measurement is from the bottom of the frame rail to the center of the bottom bolt of the shock . This process is set out in the chassis maintenance manual. If your handy with tools, you can buy the FL workshop manual on line for like 25.00 its a worthwhile investment. Good luck and if you own a motor home its a good investment to learn your way around it.
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Old 02-13-2021, 04:11 PM   #9
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Just a heads up on a potential air system problem. Hearing a new sound in the driver's compartment of my 2012 Itasca Meridian 34Y, I proceeded to search. Finally found the source being a hairline crack in the rear of the instrument gauge containing the two air pressure displays allowing air from the air system to escape. A review of IRV2 found a rash of this problem around 2007-2008. A call to Freightliner found the cost of this gauge being $800 to $900. I am going to try to first inject some epoxy alongside the metal insert to see if that might plug the air leak before purchasing a new gauge. Was hoping that if anyone else had encountered this problem, they might advise of a better fix.

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Old 02-16-2021, 10:46 PM   #10
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Drain your primary/wet and secondary tanks every month or two ,especially in more humid conditions, change out your air dryer filter every year or two depending on mileage, and grease your brake pots once a year. Inspect your tanks, lines ,fittings and air bags when you grease your brake pots. This isn't necessarily the gospel, but it covers the basics.
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Old 02-17-2021, 06:11 AM   #11
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Drain your primary/wet and secondary tanks every month or two ,especially in more humid conditions, change out your air dryer filter every year or two depending on mileage, and grease your brake pots once a year. Inspect your tanks, lines ,fittings and air bags when you grease your brake pots. This isn't necessarily the gospel, but it covers the basics.
Could you explain how you grease the brake pot please?
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Old 02-17-2021, 09:48 AM   #12
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Could you explain how you grease the brake pot please?
It’s not the chamber, but all the exterior moving parts associated with it. This is the basic maintenance routine:

Slack Adjusters

Proper alignment plays a role in the effectiveness of your heavy-duty brakes. Slack adjusters are responsible for maintaining proper alignment each time your air brake is used.

Semi-trucks can be equipped with either manual slack adjusters or automatic slack adjusters. Since the automatic variety doesn't require frequent hands-on adjustment, it can be easy to overlook the importance of keeping the slack adjuster greased.

Slack adjusters are equipped with an operating rod that helps push out any slack on the adjuster. The movement of the rod activates the S-cam, which allows for proper braking. The rod needs to be greased often using a quality lithium grease to ensure it doesn't get stuck and leave you without the ability to bring your semi-truck to a safe stop.
S-Cams

Once the slack in the adjusters has been eliminated by the movement of the operating rod, the S-cams will begin to turn. The S-cams are what push the brake shoe into the brake drum to actually bring your semi-truck to a complete stop.

Bushings are included on each S-cam in your truck's braking system. You need to grease these bushings on a regular basis to ensure that they continue to function properly. If the bushings lock up due to a lack of lubrication, you will lose brake capacity. Dry bushings can also cause slack adjusters to begin overstroking, which can lead to premature wear of the brake drum and shoes.

Bushings should be greased a minimum of each time you change out the brake shoes on your truck. You should inspect the S-cams between shoe changes to see if additional lubrication is required to maintain braking performance.
Clevis Pins

Another critical component in the function of a semi truck's braking system is the clevis pin. Clevis pins are specialized fasteners that are designed to allow the parts connected to them to rotate or swivel around the connection point.

The clevis points in a heavy-duty braking system helps to detect and maintain stroke clearance of the operating rod within the slack adjusters. Clevis pins can seize up if they are not lubricated properly.

Seized clevis pins can compromise the entire braking system, which makes maintaining them a high priority for any driver. The best way to keep clevis points moving freely within your truck's air brake system is to apply an anti-binding lubricant directly to each clevis pin whenever you invest in a lube service for your truck chassis.

Page 5 of this: https://www.dexteraxle.com/docs/defa...rsn=3b75e148_0 (view from the other side of the chambers)
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Old 02-17-2021, 09:36 PM   #13
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Could you explain how you grease the brake pot please?
Yeah BigD,
I too was wondering what a "Brake Pot" was!
Scott
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Old 02-17-2021, 11:08 PM   #14
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