July Pre-Trip Inspection at 47°C
It is 06:30 in July and the outside temperature is already 47°C. You are due to take a refrigerated 18-tonne rigid truck from Shuwaikh to Doha Camp, a 90-minute run. During the pre-trip inspection you find: coolant at the MIN mark; the left front tyre has a bulge the size of a golf ball on the sidewall; with the engine off, the air-pressure gauge falls from 8.5 bar to 6.8 bar in three minutes; the brake-pad wear warning lamp is on; and the refrigerant unit starts but cuts out after 30 seconds. The truck started normally and the engine idles smoothly. The delivery is pharmaceuticals and the customer has a 09:00 appointment. Your company defect policy says any tyre with a sidewall bulge, any air leak exceeding 0.5 bar per minute, and any red brake warning are no-go defects. You have a phone and a workshop 12 km away.
1. Sort the findings into no-go, monitor, and service-item categories, and justify each.
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No-go defects: the left front tyre sidewall bulge, because a bulge means internal casing damage and the tyre can fail at speed or under heat; the air-pressure loss, because 8.5 to 6.8 bar in three minutes is 1.7 bar in three minutes, or about 0.57 bar per minute, which exceeds the company's 0.5 bar per minute limit; and the brake-pad wear warning lamp, because it indicates a brake system fault or worn linings and the vehicle may not stop safely. Service or monitor items: coolant at MIN should be topped up and the system checked for leaks, but it is not by itself a no-go if the engine is cold and the level can be corrected; the refrigerant unit cutting out after 30 seconds is a cargo-protection problem and must be fixed before loading pharmaceuticals, because the cold chain may fail even if the truck drives. The engine idling smoothly does not clear any of these defects.
2. What brake and air tests should you perform, and why is the 3-minute leak-down result significant?
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Build air pressure to the governor cut-out, stop the engine, and watch the gauge without touching the brake pedal to check for system leakage. Then apply and hold the service brake and watch for a further pressure drop. Listen for leaks around the brake chambers, hoses and drain valves, and check that the low-pressure warning and protection valves work. The 3-minute result matters because it is a measured leak rate, not a guess: 1.7 bar lost in 3 minutes is about 0.57 bar per minute, above the company limit. A system that leaks that quickly may lose pressure during repeated braking, cause the spring brakes to apply unexpectedly, or reduce braking performance on a hot run. The vehicle should not be loaded or driven; the defect needs workshop diagnosis.
3. The dispatcher suggests swapping the tyre and topping up coolant to save time. What is your response and what should be documented?
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A tyre swap may be acceptable only if a correctly rated spare is fitted and the workshop checks the wheel and hub, but it does not address the air leak or the brake warning. Topping up coolant does not prove the cooling system is sound in 47°C heat, and the refrigerant unit still needs attention before a pharmaceutical load is accepted. My response is that the vehicle is not roadworthy for this trip as presented. Document each defect with a photo where possible, the pressure readings and timings, the warning lamp, and the refrigeration cut-out. Raise a work order, notify the dispatcher in writing, and request a replacement vehicle or a workshop repair. Do not sign a pre-trip sheet as 'roadworthy' to save the delivery slot.