Identifying Duramax Diesel LB7, LLY, LMM, LBZ Overpower Engine Breakdown or Non-Function Due to Aftermarket Power-Up Devices vs. Non-Overpower Engine Non-Function of Pistons, Cylinders and Valvetrain

This bulletin is being revised to add additional information on identifying fuel related Aftermarket Power-Up Devices. Also a Caution statement was added regarding likely Powertrain damage and warranty. Please discard Corporate Bulletin Number 06-06-01-007A (Section 06 -- Engine/Propulsion System).

Caution: Customers should be informed if a hard part failure is observed in the engine, transmission, transfer case and/or other driveline components, it is likely that powertrain components were weakened to the point of premature failure, while subjected to the higher stresses from Aftermarket Power-Up Devices. Failures associated with the installation of Aftermarket Power-Up Devices, which have been verified, are not covered under the terms of the New Vehicle Warranty.

Important: General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. Refer to bulletin number 04-06-04-054 -- Warranty Admin. - Non-GM Parts and Accessories (Aftermarket).

Important: For further information on aftermarket power-up kits, refer to February 2006 Emerging Issues Course Number 10206.02D. In Canada, information on aftermarket power-up kits will be covered in the April 2006 TAC TALK program.

Aftermarket power-up devices are non-approved by General Motors. These devices are usually piggy-backed in the main engine harness or remain connected to the diagnostic connector to upload the calibration to the ECM. Recent warranty reviews of returned engines show engine breakdown or non-function due to power-up devices that are utilized for increased horsepower and torque. The following information will assist technicians in identifying overpower engine breakdown or non-function due to aftermarket power-up devices vs. non overpower engine breakdown or non-function.

Non-GM parts can alter the design of the vehicle. GM dealers need to be aware of the quality of parts being installed on vehicles. If failure occurs as a result of installation of sub-par parts, warranty coverage may be denied. Refer to Service Bulletin Number 04-06-04-054 Warranty Admin. -- Non-GM Parts and Accessories (Aftermarket).

Installed Power-Up Kit

Aftermarket power-up kits have become a very popular add on for performance-minded customers. These devices can add horsepower and torque and can add additional stress to the engine. These aftermarket calibrations take the Duramax™ powertrain outside of its design torque and horsepower rating. They do this by altering air/fuel ratios and injector timing, resulting in excessive cylinder pressure and temperature. When these calibrated parameters are altered, it will upset the design balance and can lead to a reduction of engine life expectancy. Generally, in inspection of Duramax™ engine failure due to power-up failures, two or more cylinders will be affected.

Installed Power-Up Kit

Duramax™ Powertrain Horsepower / Torque Ratings

The following horsepower and torque increase over the past years required new internal components to accommodate the increase.

LBZ Improvements

To reliably achieve an increase in 50 horsepower with 45 ft/lb torque, the Duramax ™ diesel had to be revised in many areas. A few of the revisions on the 2006 LBZ were:

Duramax™ Life Expectancy

The Duramax™ 6.6L V8 Turbo Diesel Engine is sold with a warranty of 100,000 miles/160,000 kilometers. The Duramax™ has been tested to survive upwards of 200,000 miles/320,000 kilometers. The Duramax™ powertrain is designed for reliability, peak horsepower and torque within its design limits. When a customer installs a power-up device, it drastically reduces the mileage ratings.

Important: Cylinder Wall Spotting (commonly referred to leopard spots) is from the induction hardening process of the top 1/3 of the cylinder wall. This is normal for the Duramax ™ Diesel.

Identifying Fuel Related Aftermarket Power-Up Devices

Aftermarket companies have developed a performance pressure relief fuel valve for Duramax™ diesel engines. Refer to above graphic illustration. The performance pressure relief fuel valve attaches to the fuel rail in place of the OEM valve and will not allow any fuel return to the tank, giving 100% of the fuel to be available for additional engine performance. This may cause additional fuel related driveability concerns and may set the following DTC'S:

Aftermarket companies have developed a replacement performance/economy fuel injector nozzle. Refer to above graphic illustration. The performance/economy fuel injector nozzles replace the OEM fuel injector nozzles. The aftermarket companies claim increased horsepower, improved fuel atomization, lower exhaust gas temperatures and increase fuel economy. This may cause additional fuel related driveability concerns and may cause internal engine damage to the pistons and fuel injector nozzles.

Identifying Overpower Engine Premature Wear and Breakdown

When premature wear and breakdown is encountered due to an aftermarket power-up device, it has some very specific characteristics to the internal engine components. The following list will assist in identifying these characteristics as you tear down the engine.

The following pictures show results of overheat, overspeed, low/no oil pressure or injector breakdown and how they differ from aftermarket power-up device premature wear and breakdown.

Engine Overheat

Overheat can be caused by a loss of coolant or a general cooling system failure. Some of the indicators of overheat are:

Engine Overspeed Causes

If an engine has been run faster than design capability (redline), and has caused damage as a result, it may be a result of one of the following conditions:

Engine Overspeed Results

The following are indicators that an overspeed event took place:

Lack of Oil Pressure

Lack of lubrication causes rapid bearing wear or bearing to seize.

Bearing failure. Spun main bearings.

Engine Premature Wear and Breakdown Due to Improper Function of Fuel Injector

A fuel injector may fracture a piston or melt a piston but the damage will be limited to that cylinder only and all other pistons and cylinder walls are OK. In some cases hydraulic lock will occur on the suspected cylinder with an over-fueling fuel injector. Hydraulic lock on the suspected cylinder will cause a bent connecting rod. This can be verified with piston protrusion measurements.

Important: Copy aftermarket power-up kit check list when performing an engine disassembly investigation of overpower engine breakdown or non-function.

Aftermarket Power-Up Kit Check List

1. Piston cracked parallel to wrist pin.

•	Piston cracked in lip area.

•	Hole in piston connecting top of piston to oil cooling channel.

2. Melted Pistons.

•	Lip of combustion bowl melted.

•	Top of piston melted / missing.

3. Cross hatching polished off cylinder wall. Cylinder wall missing crosshatch on major thrust face of cylinder below ring belt travel.
4. Piston pin bore, Wrist pin, and Rod bushing.

•	Scoring in upper piston pin boss/black discoloration/oil coking.

•	Wrist Pin Wear.

•	Rod bushing surface worn and discolored.

5. Carbon coking to underside of piston.

•	Discoloration of underside of Piston.

•	Discoloration and carbon coking buildup on underside of piston between piston pin bosses.

6. Accelerated rod / Main Bearing wear.

•	Fretting on backside of bearing.

•	Bearing surface distressed.

How to handle an engine failure suspected due to a power up Device

Dealers should not automatically decline warranty assistance on engine failures due to the fact that a power-up device or modification is evident or suspected. The technician must identify that the failure is due to a power-up device by teardown analysis and diagnosis of the engine components. The following steps should be taken if an engine failure occurs and it is suspected that the modification or addition of a power-up device maybe the cause of the engine failure. If unclear of this process or direction feel free to contact your District Service Manager (DVM) (in Canada, DSM) for further support.

1. The technician should use proper engine diagnostics to lead him/her to the failed engine components. The attached check sheet should be followed and if it is determined that at least three of the check sheet items match the engine component failures then it can be decided that the failure is not a warrantable claim.
2. Engine failures that meet at least three criteria of the check sheet are considered failures that are not manufacturers defects in workmanship or materials
3. The dealership should contact the PQC, open a case to review the findings and make the final decision on warranty coverage. The DVM (in Canada, DSM) should be notified of the PQC decision.
4. Denied claims should be documented as follows:

a. The check sheet completed with the technicians detailed written findings of his diagnosis on the repair order.

b. Photographs of the failed parts should be maintained in the RO file.

5. The customer should be advised that the failure of their engine was not due to a manufacturer's defect in workmanship or materials and therefore the warranty claim is denied on this failure.