Engine Noise Diagnostic Procedures – General Information
NOTE: When diagnosing engine noise problems, make sure that noises caused by accessories, such as the air compressor and power take-off, are not mistaken for engine noises. Remove the accessory drive belts to eliminate noise caused by these units. Noise will also travel to other metal parts not related to the problem. The use of a stethoscope can help locate an engine noise.
Engine noises heard at the crankshaft speed, engine rpm, are noises related to the crankshaft, rods, pistons, and piston pins. Noises heard at the camshaft speed, one-half of the engine rpm, are related to the valve train. A handheld digital tachometer can help determine if the noise is related to components operating at the crankshaft or camshaft speed.
Engine noise can sometimes be isolated by performing a cylinder cutout test. Refer to Procedure 014-008 in Section 14. If the volume of the noise decreases or the noise disappears, it is related to that particular engine cylinder.
There is not a definite rule or test that will positively determine the source of a noise complaint.
Engine-driven components and accessories, such as gear-driven fan clutches, hydraulic pumps, belt-driven alternators, air-conditioning compressors, and turbochargers, can contribute to engine noise. Use the following information as a guide to diagnosing engine noise.
Fuel Consumption – General Information
The cause of excessive fuel consumption is hard to diagnose and correct because of the potential number of factors involved. Actual fuel consumption problems can be caused by any of the following factors:
Before troubleshooting, it is important to determine the exact complaint. Is the complaint based on whether the problem is real or perceived, or does not meet driver expectations? The Fuel Consumption – Customer Complaint Form (on the next page) is a valuable list of questions that can be used to assist the service technician in determining the cause of the problem. Complete the form before troubleshooting the complaint. The following are some of the factors that must be considered when troubleshooting fuel consumption complaints.
Additional vehicle factors, vehicle specifications, and axle alignment can also affect fuel consumption. For additional information on troubleshooting fuel consumption complaints, see Troubleshooting Excessive Fuel Consumption, Bulletin 3387245.
Fuel Consumption – Customer Complaint Form
Customer Name/Company __________________________________________________________ Date ________________
Answer the following questions. Some questions require making an X next to the appropriate answer.
IF ANSWERED YES, FILL OUT THE DRIVEABILITY/LOW-POWER/EXCESSIVE FUEL CONSUMPTION CHECKLIST, AND GO TO THE ENGINE POWER OUTPUT LOW TROUBLESHOOTING SYMPTOM CHART.
IF, AFTER FILLING OUT THIS FORM, IT APPEARS THAT THE ISSUE IS NOT CAUSED BY VEHICLE FACTORS, ENVIRONMENTAL FACTORS, OR DRIVER TECHNIQUE, FILL OUT THE DRIVEABILITY/LOW-POWER/EXCESSIVE FUEL CONSUMPTION CHECKLIST, AND GO TO THE FUEL CONSUMPTION EXCESSIVE TROUBLESHOOTING SYMPTOM TREE.
This Page Can Be Copied for Your Convenience.
In addition to the information that follows, a service publication is available titled Technical Overview of Oil Consumption, Bulletin 3379214.
Cummins Inc. defines ”acceptable oil usage” as outlined in the following table.
Coolant Loss Pre-Troubleshooting Guide
Before troubleshooting, it is critical to know where the coolant is being lost. It is not always obvious where the missing coolant has gone.
Before troubleshooting, it is important to determine the exact complaint by interviewing the driver, looking at the service history and looking at the ECM information.
Driver Interview Questions
Engine Serial Number (ESN):
What is your complaint?
How is this engine used?
What sort of load factors?
Where is the vehicle driven?
Service History Review
Repeat cylinder head or cylinder gasket repairs can indicate the problem is likely not the cylinder head or cylinder head gasket. Repeat problems can indicate a deeper problem in the engine. Keep this information in mind while going through the troubleshooting procedure.
Look at the engine’s warranty claims history:
At this point, where is the coolant is going?
If not and the coolant loss is not severe, suggest mounting a catch bottle on the radiator overflow tube to catch any overflow that can possibly be blowing out and becoming lost while at speed. Send the vehicle out to collect more data about where the coolant is not going. If the catch bottle has some coolant in it, refer back to the Coolant Loss External (out the overflow) interview questions.