Under the Hood – December 2008

Safety Recalls
The National Highway Traffic Safety Administration has issued the following recalls:

• Seven model year 2007 and 2008 Western Star 4900EX trucks fail to comply with the requirement of Federal Motor Vehicle Safety Standard 108 (Lamps, Reflective Devices and Associated Equipment). Additional marker lamps were installed between the required identification lamps and clearance lamps on the top of some truck cabs. Additional lamps located on the same horizontal line near the identification lamps may make it difficult for other drivers to distinguish larger vehicles under some conditions. The additional marker lamps must be removed.

• The size 14 service chamber of certain Bendix front air disc brakes on 86 model year 2009 Kenworth T660, T800, W900 and Peterbilt 386, 365 and 388 trucks may have been contaminated with grease between the piston head/plate and the diaphragm. When braking pressure is applied, the grease may allow the piston head/plate to slip off center and catch on the reducing ring of the size 14 service chamber. The catching of the piston head/plate on the reducing ring may lock up the corresponding front air disc brake, which may impact the operator’s ability to steer or control the vehicle.

  Both front air disc brake size 14 service chambers need to be replaced.

• The castle nut that retains the steering drag link to the pitman arm on 5,606 model year 2006 to 2008 Workhorse W42 commercial chassis may have been tightened improperly during assembly. The improper torque may have damaged the castle nut and compromised the integrity of the connection. If the drag link were to separate from the pitman arm, the driver would not have directional control of the vehicle possibly causing a crash. The castle nut that retains the steering drag link to the pitman arm needs to be replaced and tightened properly.

Revised Battery-To-Battery Connector Cable
A revised battery-to-battery cable (Part No. 21178749) for Mack CXU, CXP, CXN, CHU, CHN, GU, CTP, CT, MRU, MR, LEU and LE chassis equipped with a three-battery arrangement is available.

The revised cable, which connects the batteries of a three-battery arrangement together in parallel, does not have the rubberized plastic material molded over the brass terminal ring on the center terminal. (See Figure 1.)

The absence of this material allows stacking of other cables on the battery terminal.

Low-lube Transmission Failures
There have been several instances of transmission failures caused by lack of lubricant, according to Roadranger.

Many OEMs have incorporated the transmission oil cooler in the radiator sump. When a radiator of this design is repaired or replaced, a significant amount of lubricant can be lost through the transmission cooling system and the lube level in the transmission can run low.

Transmissions operated with that low level of lubricant will fail prematurely.

Use the following procedure to ensure the transmission lubricant level is full:

• Check the transmission lube level and fill with compatible lubricant.

• Run the engine for five minutes.

Exhaust Tie Rod Mounting Bracket
A revised frame-mounted exhaust tie rod bracket (Part No. 21159945) for Mack CXN and CHN models equipped with either single or dual exhaust systems is now available to replace the original bracket (Part No. 19QL462M).

This new bracket is of a more robust design to prevent bending fatigue failures which can occur in certain severe applications.

If you encounter a broken frame-exhaust tie rod mounting bracket, use the revised bracket as a service replacement. (See Figure 2.)

Rocker Shaft Oil Transfer Tube Installation
On Mack MP7 engines, it is possible to install the rocker shaft oil transfer tube between the engine brake control valve or intermediate section (non-brake engine) and the rocker shaft incorrectly when reinstalling the oil transfer tube.

Failure to follow the proper installation procedure may result in engine failure.

If you find an incorrectly installed oil transfer tube is the cause of engine failure during a failure analysis, the warranty claim may be denied.

Use the following procedure to install the oil tube:

• Replace the O-ring at the bottom of the control valve.

• Clean the control valve oil tube and replace the O-ring.
• Lubricate the tube hole in the rocker arm shaft and the O-rings on the tube.
• The oil tube has a flange and a bead on each end. While the flanges are the same size, the beads differ. One bead is 15.4mm, and the other is 17.3mm. Insert the small diameter beaded end of the oil tube into the oil hole of the control valve. Position the larger diameter beaded end of the oil tube toward the rocker shaft. (See Figure 3.)

  If the oil tube is installed incorrectly with the large end in the control valve and the small end in the rocker arm shaft, oil leaks will occur. This may cause oil starvation in the rocker arms, resulting in possible engine failure.

To correct:

• Seat the large end of the oil tube in the rocker arm shaft by pressing on the control valve with the heal of your hand. This allows the control valve mounting bolts to be installed. Torque-tighten the bolts to the proper specification.

Servicing Cam Brakes
According to ArvinMeritor, when servicing cam brakes, take time to replace all the springs, anchor pins, bushings and rollers. This includes replacing the cam brake return springs each time cam brakes are relined.

The return springs are critical to the alignment, the accurate return of the brake away from the drum and brake adjustments with the automatic slack adjuster.

Inspect the entire brake structure for wear, cracks or other damage. Replace damaged parts with new rather than welding or repairing. Lubricate the cam brake assembly as required.