A heavy-duty off-highway dump truck equipped with 'wet disc' service brakes reports inconsistent braking performance, especially during prolonged descents. The operator also notices that the hydraulic oil temperature for the brake system seems higher than usual. What is a probable cause for these symptoms?

Question: A heavy-duty off-highway dump truck equipped with 'wet disc' service brakes reports inconsistent braking performance, especially during prolonged descents. The operator also notices that the hydraulic oil temperature for the brake system seems higher than usual. What is a probable cause for these symptoms?

Answer options:

• Glazing of the wet disc friction plates. ✅ Insufficient cooling flow through the brake oil cooler.
• Excessive air in the hydraulic brake lines.
• Worn brake pedal linkage causing reduced travel.

Correct answer: Insufficient cooling flow through the brake oil cooler.

Explanation: Wet disc brakes rely heavily on proper hydraulic oil circulation for both lubrication and cooling. If there is insufficient cooling flow through the brake oil cooler, the oil temperature will rise, leading to reduced viscosity and potential boiling, which compromises braking performance and can lead to fade during prolonged use. Glazing is less common with wet discs than dry, air in the lines causes sponginess, and worn linkage would reduce application force but not directly heating issues.