PIPE AS-EXHAUST 3991365 - Caterpillar

Probable Causes
Low coolant level
Insufficient coolant flowRecommended Actions
Low Coolant Level
Check coolant level. If the coolant level is low, inspect the cooling system for leaks.If the coolant level is low, fill the cooling system. If leaks are found, perform the necessary repairs.Insufficient Coolant Flow
Use Caterpillar Electronic Technician (ET) to observe the pressure at the jacket water outlet while the engine is off. Then observe the reading during engine operation.If the reading is not reasonable or if the reading is not within specifications, install a pressure gauge near the pressure sensor at the jacket water outlet. Compare the gauge reading with the reading from Cat ET.If the reading from the pressure gauge does not agree approximately with Cat ET, troubleshoot the circuit for the pressure sensor at the jacket water outlet. Refer to Troubleshooting, "PWM Sensor".If the readings from the pressure gauge agree approximately with Cat ET, check the following components for problems:
Water temperature regulators
Radiator or the heat exchanger
Jacket water pumpMake the necessary repairs.