Mack ASET AC, Service Manual, Page: 109 / 536

Page 96
TROUBLESHOOTING
HIGH EXHAUST TEMPERATURE
Possible Cause Correction
1. Operating chassis in wrong gear ratio for load,
grade and/or altitude.
1. Instruct operator on correct gear selection for load and grade
conditions.
2. EGR gas too hot. 2. EGR gas flow rate too high or poor heat transfer due to EGR
cooler fouling. Check EGR cooler to ensure debris in the coolant
has not become lodged in the cooler fins, restricting coolant flow.
Check EGR valve operation to ensure full operation.
3. Restrictions in the air induction system. 3. Inspect air induction system. Remove restrictions and/or replace
defective parts.
4. Air leaks in the air induction system. 4. Check pressure in the air intake manifold. Look for leaking piping
and/or loose clamps. Make necessary repairs.
5. Leaks in the exhaust system (before the
turbocharger).
5. Check exhaust system for leaks. Make necessary repairs.
6. Restrictions in the exhaust system. 6. Inspect system. Make necessary repairs.
7. Improper valve lash adjustment. 7. Adjust valve lash setting to specified clearance.
8. Defective fuel injection nozzle assembly. 8. Isolate defective nozzle. Refer to item 8 in ENGINE MISFIRES —
NO CODE(S) chart.
High Pyrometer — Normal Boost
9. Loose ducting. 9. Repair loose connections.
10. Intercooler core fin obstructions. 10. Clean intercooler fins.
High Pyrometer — Low Boost
11. Intercooler core leakage. 11. Pressure-test intercooler. Remove, repair or replace intercooler if
test results are unsatisfactory.
12. Dirty turbocharger. 12. Remove turbocharger and clean.
13. Leaks in the pressurized side of the air induction
system.
13. Check for leaks. Repair as required.
14. Blockage in ducting between the air cleaner and
the turbocharger.
14. Check for blockage and repair.
If VTG turbocharger vans are open more than desired, pre-turbine temperatures increase:
15. Leaking actuator diaphragm. 15. Replace actuator.
16. Chassis air supply leaks causing low pressure. 16. Repair air leak.
17. Seized vane assembly. 17. Free up vane assembly.
5-111.bk Page 96 Monday, July 10, 2006 2:26 PM