Take Care of Your Air

by John G. Smith

TORONTO, Ont. – Brake adjustment tends to be the focus of inspections that determine whether your equipment can stop on demand. Measure the distance a pushrod has to travel before pressing a brake shoe against a brake drum, and you can tell if the remaining “reserve” stroke is long enough to make a heavy brake application.

Yet the unseen force behind this stopping power is often overlooked.

“If you don’t have air in the system, you don’t have anything,” says Dale Holman of Truck Watch Services, a Georgetown, Ont. company specializing in brakes. “But we’ve had that so beat into our heads, that brake adjustment is everything.”

However, there are some simple steps you can take to ensure that your brakes aren’t starved of the air that controls them.

1. Clear your gladhands

It may be a small hole, but there’s plenty of room for debris in the gladhand opening that connects trailer brakes to their supply of compressed air. Holman has found the orifice clogged with everything from grass to beehives, bugs and cigarette butts. (Apparently someone was too lazy to stroll over to a yard’s ash can.)

Clogging can mean a slower brake response, says Rolf VanderZwaag, the Ontario Trucking Association’s manager of maintenance and technical issues. A gentle brake application can still send air through a soft mass of grass like a breeze through a wheat field. But a hard brake application will compress the debris and block the passage altogether.

“You have a small air line at the end of that (gladhand),” Holman explains. “As soon as you take that wadding and drive it in there, nothing is going to get through.”

Instead of limiting yourself to traditional gladhand seals, consider versions that incorporate protective flaps. (However, the flaps themselves can rip off and offer their own form of debris, so VanderZwaag also suggests placing a screen between the seal and the airline.) A variety of products, such as the Sloan Gladhand Pacifier – which, as its name implies, looks like a baby’s pacifier – will protect openings when tractors and trailers are uncoupled.

At the very least, ensure gladhands are free of debris before twisting them in place.

2. Thaw with care

Alcohol is often used to thaw frozen brake components, but it can choke air supplies when used incorrectly.

Approved de-icers should only be poured into the emergency side of an air system, identified with a red gladhand. Haldex, a maker of brake components, approves methyl alcohol, but bans everything from isopropyl alcohol to ethylene glycol antifreeze.

The latter fluids will swell O-rings within brake valves, and will break down the lubricants that protect internal pistons controlling the flow of air.

Fluids poured into the blue gladhand marking the application side of your brake system will only sit on top of a valve’s piston and keep it from opening when air should be allowed to pass.

Meanwhile, the alcohol also needs a path to travel. “If you don’t drain an air tank first, you’re going to pour gallons of alcohol in the front, and it’s not going anywhere,” Holman says, referring to the way air can fill a reservoir and not allow anything else to pass. “It (the alcohol) is just going to go to the lowest point in the air line and sit there.”

A little solution will also go a long way since it’s the vapor – and not the alcohol itself – that thaws the frozen components.

“I’m saying use an eighth of an ounce, not half the jug,” VanderZwaag says. “Besides, if you’re considering it in the first place, what you should be asking yourself is, ‘Why do I have moisture in the air brake system?'”

3. Keep it dry

Air dryers are standard equipment in northern climes.

After all, it’s the moisture in the air that can freeze, and even the smallest particles of ice can jam the internal workings of a brake valve.

Still, that doesn’t mean an air dryer can be forgotten. VanderZwaag recommends replacing its desiccant during annual winter maintenance schedules, even though manufacturers might be willing to let you adopt longer intervals.

All cartridges filled with this water-absorbing material aren’t created equal, he adds, recommending Original Equipment replacements. Cheaper materials are prone to breaking down under the stresses of the job.

4. Spec’ the right supply

Compressors and air dryers come in different sizes for a reason. A 13.5 cfm compressor that offers plenty of air for a tandem-tandem combination’s brake applications may not be able to keep up with the needs of a multi-axle “Michigan combination” trailer – even if you do have a drivetrain capable of pulling the load.

“This system is going to be strapped to the limit,” VanderZwaag says. With more than eight axles, a tractor-trailer needs a compressor that can pump out 20cfm of air. “And you need to the air dryer to go with it.”

At the wheel, you may not notice much of a difference if your components are under-sized, although the air gauge will show the compressor kicking in more often than usual.

But the brakes may be starved of air when you begin applying them on a regular basis, travelling down a hill or snaking through stop-and-go traffic.

Meanwhile, under-sized air dryers will run hotter, break down their desiccant and feed it through the air system, where it can clog the tiny orifices within an ABS valve and rob you of your brakes.

5. Question your gauges

A glance at the air gauge can’t be your only test of air supplies, Holman adds, referring to one tractor that he inspected.

Even when the air was drained, the needle still pointed at 120 psi.

“The line had been pinched and air was getting in and staying, keeping the pressure up,” he says.

The solution is to fan your brakes during a circle check – simply pump away at the brake pedal until the warning buzzer sounds – and watch the needle climb back.

“When you hear the air dryer blow off, you hear that ‘psew,’ how far up is it going?” he asks, referring to the sound created when an air dryer expels moisture with a blast of air once the compressor reaches its cut-out pressure.

“If it’s only going up to 100 or 105 psi, you haven’t got enough air. Two or three brake applications and it’s toast. If you do two or three brake applications and your low air warning buzzer comes on, you’ve got a problem. You should be able to do seven full brake applications.”

6. Take care with a torch

An open flame of a torch can be your air system’s worst enemy. While some truckers and mechanics might think of using a torch to thaw a frozen brake valve, the heat can melt the rubber O-rings inside.

A torch can also cause grief when it’s used to repair a nearby frame.

“Air’s only as good as the smallest hole it has to travel through,” Holman says, referring to one fleet that unknowingly damaged dozens of service lines when it welded brackets to trailer coupler plates. The plates heated up, and the adjacent lines melted inside.

“Because they didn’t put direct flame on it, it didn’t get a hole in it and they think it’s fine,” he says.

His solution is to place a piece of wood between the frame and the airline before applying the torch.

They’re simple steps, but they’ll all help ensure that your brake system isn’t choked of the air that gives it life.

Next month: Better brake

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