Muffler-To-Vertical Exhaust Pipe Clamp
On January 15, 2001, on Mack CX and CH models and January 29, 2001, on all other models, a new five-inch exhaust pipe clamp (Part No. 11ME348M) was phased into production and replaces the previously used clamp (Part Nos. 11ME330M and 11ME330M3).

This clamp, which is used at the connection between the muffler and the vertical exhaust pipe, provides a more positive seal and a more secure joint. When replacing an existing 11ME330M or 11ME330M3 exhaust pipe clamp, use the new clamp and tighten it to 35 to 45 lb.-ft.

Effective June 11, 2007, a five-inch U-bolt style exhaust pipe clamp (Part No. 83AX840) was implemented into production on CXN model chassis. This U-bolt style clamp is used in addition to the existing clamp and is installed below the existing clamp.

When used in conjunction with the existing clamp, a more secure exhaust pipe-to-muffler joint is provided. When installing the U-bolt, install it on the muffler outlet above the weld and below the existing clamp. Orient the clamp in any position. The torque specification for the U-bolt style clamp is 40 lb.-ft.

Revised Oil Filter Mounting Bracket Gasket
After an extended period of time in service, oil seepage may occur at the oil filter mounting bracket-to-cylinder block on Mack E-Tech and ASET engines. To eliminate this condition, Mack has a revised oil filter mounting bracket gasket (Part No. 590GB345A).

The revised gasket is made from an improved material that includes an anti-stick coating and has a steel core to provide less fastener torque loss and improved sealing.

Service gasket kits which include this gasket have been updated to include the revised gasket. To reflect this change, an “A” has been added to the end of the service gasket part numbers.

O-ring Aids In Break-in
On Caterpillar C-15 (S/N: MBN1-Up; 6NZ1-Up and 9NZ1-Up), C-16 (S/N: 7CZ1-Up), C-18 (S/N: MEP1-Up), C11 (S/N: KCA1-Up), C13 (S/N: KCB1-Up and LEE1-Up) and C15 (S/N: BXS1-Up; MXS1-Up and NXS1-Up) on-highway engines, the O-ring on the tip of the fuel injector does not cause the fuel injector to fail.

The O-ring is only an aid during the break-in period of the engine. It is only needed until a “carbon-dam” is built up during break-in. It is normal for this O-ring to be burnt, cut and damaged after it has been run in the engine.

Engine Oil Dye
Dye has been added to the engine oil on Caterpillar C7 (S/N: C7S1-Up) and C9 (S/N: C9S1-Up) engines in order to help detect oil leaks. The dye, which is added at the factory, can be used to detect oil leaks during early hours of operation. Use a black light to detect the leaks. The dye will appear bright yellow under a black light.

Improved Oil Level Gauge
Caterpillar now is using an improved oil level gauge in C7 (S/N: C7S1-Up) and C9 (S/N: C9S1-Up) engines. The previous gauge was difficult to insert into the tube assembly resulting in bent gauges and difficulty keeping the gauges locked in place.

An improved oil level gauge is being used to prevent the gauge from bending in the tube assembly. The gauge was modified by adding an additional twist and increasing the size of the ball at the tip of the gauge to one-quarter inch.

Valve Yoke Installation
Mack MP7 and MP8 engines utilize pinless valve yokes at the inlet and exhaust valves, similar to the pinless yokes used on previous Mack engines such as the ASET and E-Tech. The holes on the bottom of the yoke that fit over the valve stem tips are round on one end and elongated on the other. The yokes are not symmetrical. From the centerline of the yoke pad, the end with the round hole is shorter than the end with the elongated hole.

It is extremely important that the valve yokes be installed with the elongated hole over the outboard valve, away from the camshaft (toward the inlet manifold). If the end of the valve yoke with the elongated hole is installed over the inboard valve (toward the camshaft), contact with the rocker arm will occur resulting in a dropped valve and significant engine damage.

An engine failure resulting from improper valve yoke installation is not warrantable.
During rocker shaft removal, reinstallation or repositioning, a valve yoke may become disengaged from the valve stem tip. If this is not corrected prior to starting the engine, major engine damage will result.

Take extra care during rocker shaft removal and reinstallation to ensure all yokes are engaged properly with the valves, and valves must be readjusted whenever the rocker shaft has been removed and reinstalled.

Exhaust valve yokes used on PowerLeash-equipped engines are of a different design and not subject to the improper installation described above.

The National Highway Traffic Safety Administration (NHTSA) has issued the following recalls:

  • On certain Caterpillar C7 diesel engines that were installed in 2008 Blue Bird Vision school buses, the oil fill cap may separate from the oil fill tube allowing engine oil to be emitted from the tube. Oil could wet the left front brake resulting in reduced braking capacity. This has the potential to lead to a vehicle crash. To fix the problem, the oil fill tube assembly must be replaced.
  • On certain 2005 to 2008 model year Freightliner Century ST, Classic XL, Columbia and Coronado trucks equipped with rack and pinion steering, the tie rod arm may have been installed incorrectly. The threaded end of the ball socket assembly may fracture and separate. A fractured tie rod assembly will make the vehicle more difficult to control at higher speeds and a crash could occur. Incorrectly installed steering arms need to be replaced.
  • On certain 2002 to 2007 model year Mack CH, CHN, CX and CXN trucks equipped with ASET AC model engines, the engine is configured with an external exhaust gas recirculation system which makes it difficult to service the fuel injection lines when using traditional tools. Therefore, it is possible for fuel leaks to develop when removing and installing the fuel injection lines. A leak in the fuel injection line may spray fuel on the hot surfaces of the exhaust gas recirculation system, which could result in an engine fire. Defective lines need to be replaced.
  • On certain 2008 model year Peterbilt Models 367, 386, 387, 388 and 389 trucks, the longitudinal seams on the fuel tanks were fabricated using an incorrect weld speed for the given material thickness. This resulted in a weld which did not completely penetrate the entire material thickness. In the event of a crash, fuel tanks with this defect can leak diesel fuel. Defective tanks need to be replaced.
  • On certain 2008 model year Volvo VHD, VNL, VNM and VT trucks, the hood restraint cylinder does not contain enough dampening to adequately restrain the hood. The cylinders could separate, which would leave the hood unrestrained when opening and closing. Hood restraint cylinders with this problem need to be replaced.
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