I finally finished the repower on my Crown tonight and got it off the blocks.  My batteries are expected to arrive tomorrow afternoon, and I'll be able to assess my mechanical skills shortly thereafter. Post by: Uglydog56

Once I had it on the ground, I pressurized the air system with my little electric compressor to check for leaks, since I had changed the compressor configuration.  It aired right up, but was down to about 30 psi two hours later.  I looked around and found that my fast idle was on, and it was leaking, as well as the fact that I hadn't tightened one of the fittings on the transmission high-low switch.  So, I fixed those and aired it back up.  I don't have air ride.  I replaced a lot of lines, but didn't get them all.  I know it's pretty challenging to get these old buses air-tight.  How long does the air pressure have to last to be considered acceptable? 

Post by: bevans6

The DOT (Department of Transportation) spec is three psi per minute with the brakes fully applied.  You lost approximately 90 psi in two hours; three psi per minute is equivalent to 90 psi in 30 minutes.  It's legal, but it's still a lot more than I am used to seeing.  My bus tends to bleed down that far in about 12 hours, actually sticking at 60 psi due to the protection valve.  On the road, my compressor tends to cycle on and off about every 30 minutes in normal highway driving.

Post by: belfert

I'm not sure what normal is, but my bus typically maintains air pressure above 80 psi for weeks during the summer months.  It will bleed off in a day or two in the winter.  I only have airbags on the tag axle on my bus.

Post by: Lin

My dash gauge is off the accessory tank, which will bleed down to zero within an hour.  I believe that is due to leaks in the windshield wiper valves.  I have a separate gauge in the engine compartment that drops to 85 psi as the accessory tank empties, but then remains at that level for an extended period.

Post by: Uglydog56

My gauge has two needles, a red one and a white one.  The way this was explained to me was that the white one was the "normal" air, and the red one was for the emergency brakes.  The previous owner changed it.  It originally had two pressure gauges up front. He changed one to this dual gauge and hooked the other one up to the brakes so you could see how much brake pressure you were using.  I'm going to air it up and pay closer attention today. 

Is it three psi per minute with the parking brake set, or with the brake pedal held down?  I will have to get my wife to hold the brakes while I crawl all around underneath with my hearing aids turned up.  I wish I knew more about air brakes.  I have already spoken with the local truck/RV place here; they are going to conduct a safety inspection and brake tutorial with me as soon as I can get it there.

Post by: Oonrahnjay

It's not necessary, but I have two dual gauges: one for my "wet tank", one for my main tank (rear brakes), one for my secondary tank (front brake circuit), and one for my accessory tank.  The main tank (and its air supply to the service and parking/emergency canisters on the rear axle, as well as to the brake valve on the dashboard) is the critical reading. Still, I feel that watching the pressure rise when airing up and any difference in drop is valuable information when I'm driving, and also it will be helpful in troubleshooting.

Quote from: Uglydog56

There are different specifications for "brakes applied" and "brakes not applied" (I'm not sure if these are DOT inspection standards or industry engineering norms), so I'd suggest that you investigate this one and get complete data and also context so that you can be sure that you understand what you're considering. 

Quote from: Uglydog56

Additionally, consider exploring possible Bendix air brake school locations near you.  It requires a few days and $300, but it's very complete and well worth the investment.  It covers everything you'd need to know when operating a bus with air brakes.

Post by: bevans6

Glad to hear you are going to get a tutorial and inspection - the thing about air brakes is that they are "active" brakes - a lot has to be working right for them to do even the first thing about stopping, compared to hydraulic brakes that can work pretty well with absolutely nothing working but the pedal.  So, you need to know exactly what should be happening so you can tell if it stops happening before you need the brakes "right now".

The test is part of a DOT daily inspection for all air brake-equipped vehicles. It's just a matter of having the air at 100 - 120 psi, engine off, suspension fully up, all accessories off, foot fully on the brakes, parking brake off, and see what happens.  If anything bleeds down, you should notice. The US and Canada federal test rule is three psi per minute for a bus (different for a straight truck and a truck/trailer combo).  It is a test of the full air system, including the service brakes, but not a test of the emergency brake system (on DD3 systems like mine). 

As a DOT test, you can be pulled over and tested at any time on any road, regardless of whether you are driving a private or commercial vehicle.  Not that that happens all that often, I suspect.  As part of your tutorial/inspection, you should determine exactly which part of the air system your gauges are connected to.  Dual gauges are typically used for more modern spring brake systems that feature separate front and rear tanks, with one gauge for each tank.  Some buses have the gauge connected to the accessory system; it usually bleeds out first and takes the service tank down with it, to the point where a protection valve operates.  My bus has the gauge on the service tank, AKA the "dry tank"

Post by: luvrbus

Most gauges on your vintage year coach have one needle for air pressure and another for brake-applied air pressure. The original '05 Eagle dash had the two-needle gauge for the air system.

Post by: akroyaleagle

Try this DOT test!

AIR BRAKE TEST SINGLE VEHICLE

With the ENGINE OFF, the air pressure at MAXIMUM, the wheels chocked, the spring brake released, and the key on.

1)  Air Leakage Rate

   a. Watch the air supply gauge for 60 seconds; the air loss should be no more than two psi.

   b. Apply the foot valve fully. Watch the air supply gauge for 60 seconds; the air loss should be no more than three psi.

2) Air Warning Light

     Apply and release the foot valve until the air warning light comes on; this should happen before 60 psi.

3) Spring Brake

     Apply and release the foot valve until the spring brake pops out; this should happen between 20 and 45 psi.

4) Air Build-Up Rate

     Start the engine to build air pressure. When air pressure reaches 85 psi, the time required to build up to 100 psi at idle increases. It should take no more than 45 seconds.

5) Governor Cut Off

     The Governor should cut off at about 110 to 125 psi.  You will hear air release from the system.

6) Spring Brake

    a. Remove the chock blocks.

    b. Place the vehicle in drive.

    c. Attempt to pull the vehicle forward; the vehicle should not move.

    d. Place the vehicle back in neutral.

7) Service Brake

    a. Release the spring brake.

    b. Place your foot on the foot valve.

    c. Place the vehicle into drive.

    d. Put the vehicle in motion. When the vehicle reaches the speed of 5 MPH, apply the service brake to stop the vehicle. The vehicle should stop!

Post by: Oonrahnjay

I'd also note that it's essential to perform these checks regularly.  I had to almost completely replace the brake system on my bus (lines, tanks, protection valves, brake cans, etc.) - when I finished, I aired up to 120 with shop air; it dropped to about 116 or 117 psi after an hour.  I tried again a few days later, forgot to check after an hour, and it was still holding more than 115 after an hour and a half. 

That felt pretty good to me; then I got involved in a few projects for a few weeks that made it impractical to start my bus. However, when I did, I heard some minor leaks. I aired up to 120 again, and this time I lost about 20 pounds in an hour.  So, once you get a system pretty air-tight, things can change!  Based on what I found chasing leaks, I'm pretty sure that any changes were "settling in" but it took finding them and tightening them.

Post by: luvrbus

Most states have different tests for vehicles under 29,000 pounds and those with older systems. The Federal DOT test is not per se here in Arizona or in some other states.

The newer models have such large tanks and high-capacity CFM air compressors that it's hard for one to fail. Just keep your system in good working order, and if you notice a leak, repair it.

I doubt the DOT will ever check a motorhome; otherwise, there would be a lot of RVs with the pretty red tag in the windshield. Air pressure is just one small part of a complex system.

Post by: akroyaleagle

I am appalled by the individuals who purchase these buses without having received any air brake training. Most may have never driven anything bigger than a pickup!

I have served as Director of Training and Safety, as well as Driver Trainer for a bus company, and as Supervisor and Driver Trainer for a large fleet of commercial vehicles within a GSA motor pool.

I never checked a new driver with a CDL who performed the check correctly during the test drive. It was one of the areas where I placed emphasis. While I don't do it every day in my own coach, I perform it often. I am the only driver of my coach.

Folks, there is no substitute for doing this correctly. It is the only way to ensure the system's performance.

I have never seen an Eagle '01 conversion that did not have the brakes upgraded, which could pass this test. Nearly every one of them was dangerous (in my opinion). Most of them could not have avoided an accident at low speed by getting the coach to stop.

If you do not understand this test, please ask for help. It's pretty easy. Just do it, as my other post indicates.

Post by: Lin

Although I am not minimizing the importance of checking the brakes before starting out, I will say that when I air up, release the parking brake, and begin to move, I am trying to be aware of anything that may be different or amiss.  On the one-mile dirt road from my house to the highway, I believe I have a clear picture of anything wrong.  I think that one can say there is a difference in familiarity between someone who is assigned a vehicle and a bus enthusiast who works on the coach often and drives that one frequently.

Post by: luvrbus

I have always wanted all people driving RVs with an air brake system to have a CDL or an air brake endorsement, at the very least, so that they understand how the system is supposed to work. JMO

Nowadays, computers control your brakes, which scares me. My point is that people get so wrapped up in the DOT air test that nothing else seems to matter. Who cares if it holds air for months if it doesn't stop? Another of my opinions.

I saw a 4104 and a 4106 pass the DOT test here, but it was for the older systems. No way could it pass a standard DOT inspection of today, like the one posted, with the old ICC brakes and a mechanical parking brake; those are scary without air pressure.

For years, the tandem trucks never had brakes on the front axle. It was supposed to be safer to stop with two-axle brakes than with three-axle brakes. I never could figure that one out.

Just check your brakes. Throughout the years I've owned my trucks, we've never received a ticket for brake issues from the DOT, nor have we had any lost nuts and bolts. Yes, DOT has some reasonable rules, some suck, and don't make it any safer for the public or the driver.

Post by: lostagain

I have had a Class 2 license with an air endorsement for 40 years now. It is the Canadian equivalent of a CDL for commercial buses. It is renewable here in BC every five years.

While I do a complete pre-trip once in a while, I don't do it every day while on the road on a trip. I am the only one driving my bus. I do all the maintenance and repairs on it. I am very familiar with it and how it behaves normally. I can sense anything unusual immediately and have a reasonably good idea where it originates. Before I start it in the morning, I note how much pressure was lost overnight, then once running, how fast it builds. I am always aware of how often the compressor cycles. I regularly adjust the slack adjusters on the brakes, so if the brakes feel different, I would notice.

Doing a complete pre-trip every time I move my own private coach would be anal. That being said, when I drove the hockey team's bus, which also held a commercial charter license, I performed a complete pre-trip inspection and a post-trip inspection every day that I used the coach. It is required by law, has to be recorded in the logbook, and I also felt I had a moral responsibility.

Having said all that, I know several of you out there don't know very much about air brakes and air systems, so the least you could do is learn how to perform a proper pre-trip inspection. If you find a problem, don't move until it is fixed. Although it is not required in most American states, consider taking a course.

Post by: akroyaleagle

Well said lostagain!

My point was to know how to do a proper check. I also agree that we don't need to do them every day on our own coaches, which no one else drives, for the reasons you state.

Clifford: I have always been against the requirement for a CDL for private individuals. Mainly because the "Govmint" would be involved. We all know they can't run anything right. I believe there should be a way to educate people about air brakes and the dangers of low pressure or other faults.

I've had a commercial driver's license since 1969. I keep mine current, but finally let the HazMat endorsement go last year when I renewed. I'm a little south of you in age, so I decided I would not be hauling HazMat in my coach. (And if I do, I don't want the feds involved.)

I also recall many truckers backing off the front brakes. Those were usually the same guys who drove on ice with the Jake engaged! Unless one is in a position to back it up with action, comments to them fall on deaf ears!

A complete check takes only a few minutes. With practice, it is pretty short. It hardly seems to inconvenience anyone.

That kind of distraction causes many accidents.