Recommended Diagnosis Procedure

TMC recommends technicians use the following diagnostic procedure:

1. Check if the vehicle was in for previous EGR system or performance repairs. This may provide a clue as to the problem at hand.
   1. Take special note of any turbocharger failure on the vehicle; if the cooler is contaminated with oil, it will attract soot.
   2. Always clean an EGR cooler following any major turbocharger failure during which debris could potentially enter the intake manifold.
   3. Always clean the EGR cooler whenever work was done to repair oil passing into the exhaust.
2. If the data is available, check engine oil soot rates. Soot rates vary among engines; however, if the rate determined through oil analysis increased for the engine being checked, it may indicate an EGR cooler problem.
3. Review any engine ECU fault codes that may be present.
4. Look for obvious problems, such as loose clamps, wires, external leaks (especially from the EGR system), intake leaks, etc.
5. If there is loss of coolant and no external source can be found, pull the EGR cooler inlet and outlet pipes and check for coolant contamination. Be careful not to confuse condensation in the EGR cooler for coolant. Inspect the diesel particulate filter (DPF); an EGR cooler leak can cause significant deposits to form in the DPF, and subsequent DPF regeneration problems. (See Fig 1
   Fig 1: Checking Diesel Particulate Filter Inlet Coolant Deposits

   
6. Verify the complaint. If possible, hook up to a loaded trailer and road test with a diagnostic tool connected to monitor performance and faults.
7. Verify the EGR system sensors and other engine system sensors are free from damage and are functioning properly.
8. Verify the variable geometry turbocharger is calibrated and functioning properly, if so equipped.
9. Verify the EGR valve is functioning properly as per original equipment manufacturer (OEM) specifications.
10. Verify the EGR flow sensing device is functioning properly as per OEM specifications.
11. With the engine at normal operating temperature, verify the EGR gas temperature is within the normal range.
12. If the complaint is verified and no problems were found using the steps listed above, check the EGR cooler exhaust inlet and outlet fins for signs of plugging as follows:

1. Remove the exhaust inlet and outlet hardware while leaving the EGR cooler still mounted to the engine, if possible.
2. Inspect the exhaust inlet and outlet using a small 'dental' mirror and a flashlight. A black, powdery coating of soot on the EGR cooler fins is normal. Plugging is indicated when a significant number of the passages are bridged over with a heavy coating of soot. If the coating is wet and appears like sludge, there may be an internal EGR cooler leak. If the wetness is at the EGR cooler inlet, it may indicate another engine problem which should be checked accordingly.
3. If the cooler is dry on the inlet and wet on the exhaust outlet, follow the leak test procedures described on page 4 of this RP.