Beat the Heat

Are you ready? The creeper cops are planning a one-day brake inspection blitz called Operation Air Brake on Sept. 5. It’s a continent-wide endeavour, so the only way you’ll be able to avoid it is to book some vacation time. Or you can just prepare yourself for the inevitable. Time to tune up the truck and brush up on the trip inspections so everything is ship-shape when you get hauled around back of the scalehouse.

Operation Air Brake uses the CVSA Level IV inspection criteria, focusing on brakes. Inspectors will check your low-air warning device, brake pushrod travel, lining and drum condition, and air-loss rate if a leak is detected. That said, here’s a simple, six-step inspection routine you can use to keep your brakes effective and in compliance:

1. Physical condition. First, chock the wheels to prevent vehicle movement when the brakes are released. Release the parking brakes, then build pressure until the compressor cuts out. Shut off the engine, place the transmission in gear, and, using a stick, make a full pressure brake application and hold it. Now check all the air hoses and fittings for leaks, abrasions, bubbles, or bulges in the tubing. Look for places where the hoses may contact any vehicle part. Listen for air leaks all over the vehicle.

2. Low-pressure warning. You can check the low-pressure warning device by fanning the brake pedal until the warning comes on. The engine can be off, but the key must be turned on. The device must activate at or before 55 psi, although many will come on at around 60 psi. To test the pressure build-up rate, start the engine and allow the pressure to rise to between 80 and 90 psi, then make a full-pressure brake application. The air pressure must remain steady or continue to build while the engine is idling.

3. Cut-in/cut-out pressure. Test the governor cut-in/cut-out pressure by dynamiting the tractor and trailer brakes and building pressure to 100 psi, then fanning the brakes to lower the pressure. Note the pressure at which the compressor cuts in (the pressure gauges will jump slightly when the compressor does so, and the sound of the engine will change slightly). Let the pressure build until the compressor cuts out or the air dryer expels a burst of air. The cut-in pressure should be no lower than 80 psi, and it shouldn’t take any longer than two minutes to build full pressure at idle.

4. Air-loss rate. Check the air-loss rate by releasing the tractor parking brakes and charging the trailer system. Rebuild the system pressure to its maximum, stop the engine, and then make a full-pressure brake application. The pressure will drop with the initial application, but should then hold steady. Maintain the full application for a minute or two and check the air-pressure loss rate. The pressure shouldn’t drop more than 3 psi per minute for a single vehicle, 4 psi per minute for a tractor and a trailer, or 6 psi for a tractor with two trailers.

5. Tractor protection valve. Build the pressure back up to normal operating range and close the trailer-supply valve by pulling out the red button. Leave the cab and disconnect the service-line coupler from the trailer (the blue line) and place it close to the driver’s door. Climb back in and make a brake application. If any air can be heard leaking from the end of the hose, the valve is defective. Next, check the spring parking brakes. Reconnect the service line, release the tractor parking brakes and tug against the trailer. It shouldn’t move.

6. Brake adjustment. The final step is to measure the brake pushrod travel. First, you’ll have to release the brakes and mark the pushrods at a point right up against the brake chamber housing. Most modern pushrods feature a factory-installed mark, which will show on the pushrod as it emerges from the chamber if the brakes are beyond the adjustment limit. Having marked the pushrods, you’ll need a short stick or some other means of holding the brake pedal in a position that will make and hold a full-pressure application. Release all the parking brakes, build the pressure to 100 psi, shut off the engine, and apply the brakes. Measure the distance between the mark and the face of the chamber, then check the re-adjustment limit for the chamber you’re measuring.

A brake adjustment should be performed (by qualified personnel) on vehicles with manual slack adjusters. Automatic slack adjusters can be tightened up by making several full-pressure applications and holding for several seconds. If this still yields an out-of-adjustment condition, the auto slack may be defective, and should be inspected by a brake technician.

Ideally, you should install brake-stroke indicators on the truck to simplify these inspections, but they’ll need to be installed properly and checked periodically.

If you’re working on a vehicle you’re familiar with, you can do a manual tug-test of the slack adjuster. This procedure certainly isn’t as accurate as the mark-and-measure method, but it’ll give you a ballpark idea of how well the brakes are set up. Using nothing more than your own hand, pull the slack adjuster away from the brake chamber. It shouldn’t move any more than 3/8 to 3/4 of an inch. This little inspection can be conducted in a matter of minutes in most instances, except the mark-and-measure portion, and would be useful if it was done on a regular basis, not just before brake and inspection blitzes.

During last September’s Operation Air Brake campaign, nearly 18 per cent of vehicles checked were removed from service. Fully 75 per cent of these out-of-service orders were for brakes out of adjustment. Of the nearly 93,000 brakes checked, 29,000 were equipped with manual slack adjusters and about 64,000 had automatic types. Nine per cent of the brakes with manual slack adjusters and just 3.7 per cent of the brakes with auto-slacks were placed out of service. And these numbers come from a blitz announced weeks in advance.

So listen up. Be ready-not just to pass muster with the creeper cops for a day, but to run safe all year round.