Steering Column Inspection
On certain Mack CXN, CHN, CV and CL models manufactured between January 1, 2006 and September 30, 2006, and equipped with a TRW GEN II tilt/telescopic steering column, side-to-side movement of the steering wheel may be noticed. This condition is caused by a loose tilt joint pivot.

Procedures for inspecting the steering column to verify this condition are as follows:

  • Park the vehicle on a level surface, apply the parking brake and shut the engine off.
  • Position the steering column to the fully down (compressed telescopic) and neutral tilt positions.
  • Using your two fingers and thumb of each hand placed at the 3 o’clock and 9 o’clock positions as shown in figure 1, apply a light load (less than 5 lbs.) vertically upward to one side and downward to the other side. Repeat applying the load to the steering wheel several times.
  • Excessive side-to-side deflection is evidence of an improperly seated rivet at the steering column pivot joint (see figure 2).
  • To visually confirm this condition, remove the steering column upper cover and reapply the same load as described earlier. If the condition is caused by an improperly seated rivet, you will see movement at the pivot relative to the tilt housing.

If you confirm that the rivet in the pivot joint is loose, replace the steering column.

Repairing Rocker Arms
If the rocker arm on Caterpillar C15 (S/N: SDP1-Up and B5R1-Up) engines is replaced, you also should replace the associated unit injector. Rocker arms that need to be replaced can cause damage to the internal components of the injector.

The height of the injector should be documented and the height of the injector should be adjusted on the remaining cylinders.

HEUI Fuel System High Pressure Oil Pump
For Caterpillar C7 (S/N: FML1-Up; FMM1-Up; KAL1-Up), C9 (S/N: MTB1-Up; CKP1-Up; 9DG1-Up), 3126E (S/N: HEP1-Up) engines, the sealing joint for HEUI fuel system’s high pressure oil pump has been redesigned in order to improve the sealing characteristics at the pump’s mounting flange.

The new design utilizes an O-ring face seal that will make pump installation onto the engine easier (see figure 3).

Shift Lever Detent Spring
In certain instances, gear lever disengagement may be experienced in Mack model chassis equipped with Eaton Fuller FR model transmissions. If your customer experiences this condition, an optional detent spring (Part No. 3088-4303135) is available.

The optional spring is added along with the existing gear lever detent spring.

ABS Sensor Mounting Bracket
Effective August 29, 2007, a different ABS wheel speed sensor mounting bracket (Part No. 11MN45M) was implemented into production on all Mack chassis equipped with an S462 or S522 rear axle. This change was made to eliminate an interference condition between the mounting bracket and tone wheel.

If there is contact between the mounting bracket and tone wheel, an ABS fault (MID 136, SID/FMI 003/000, 003/008, 004/000, 004/008, 005/000, 005/008, “Sensor Air Gap too Large,” “Air Gap too Large or Sensor Shorted”) will be logged.

If you encounter this condition on a chassis manufactured prior to August 29, 2007, replace the existing sensor bracket (Part No. 11MN43M) with bracket Part No. 11MN45M.

If there has been contact between the wheel speed sensor mounting bracket and the tone wheel, inspect the tone wheel for damage and replace as required.

Applying Sealant
Use the following procedure when applying Loctite Ultra Grey Flange Sealant 5699/ Meritor Part No. 2297-Z-7098 to axles.

  • Remove all old gasket material from both the axle and the carrier surface (see figure 4).
  • Clean the surfaces where you will apply the silicone gasket material, remove all oil, grease, dirt and moisture.
  • Dry both surfaces
  • Apply a .125-inch diameter continuous bead of Loctite Ultra Grey Flange Sealant 5699/Meritor Part No. 2297-Z-7098, around one surface. Also apply the gasket material around the edge of all fastener holes on the surface (see figure 5). The amount of silicone gasket material applied must not exceed a .125-inch diameter bead. Too much gasket material can block lubrication passages and result in damage to the carrier.
  • Assemble the components immediately to permit the silicone gasket material to compress evenly between the parts. Tighten the fasteners to the required torques for that size fastener.
  • Wait 20 minutes before filling the assembly with lube.

Shift Bar Housing
Mack MR and MRU models used in certain vocational applications (predominantly concrete pumping operations), may experience oil leakage at the transmission shift bar housing-mounted breather when the engine is operated in PTO mode at a steady-state high idle.

If you discover this condition, a revised aluminum shift tower space plate (Part No. 31KD336M), which provides a port to relocate the breather to the shift tower, is available.

The existing breather (Part No. 3088-4304602) can be reused.

Aluminum Radiators Need Extra Care
With aluminum radiators and heater cores becoming more common, the National Automotive Radiator Service Association (NARSA) in Pennsburg, Pa., cautions that these components require more detailed attention than their traditional, copper/brass counterparts. Aluminum radiators and heater cores provide better heat transfer than copper/brass, says NARSA, and can reduce vehicle weight and packaging requirements. They are susceptible, however, to conditions that are not as critical in traditional systems and can fail if technicians overlook specific maintenance details.

NARSA recommends using a 50/50 mix of organic-acid-technology (OAT) coolant and water; checking the system every two years or 24,000 miles; not mixing coolant types; and adhering to manufacturers’ recommendations.

Two checks technicians are probably not accustomed to making on traditional systems – but which are important for aluminum systems – are pH level and electrolysis.

Incorrect pH levels (too acidic or too alkali) will accelerate cooling system corrosion causing aluminum components to pit and flake. The flakes enter the coolant and remain in suspension until they reach a cooler area, where they drop out and build up until the system is clogged. This is called transport depositing.

A pH reading between 7.7 and 9.3 is considered acceptable.

Electrolysis means there is stray electrical current within the cooling system – often because of poor grounds at major electrical components. Excessive voltage (over 0.1 volts) causes the coolant to become an electrolyte, promoting galvanic corrosion and, often, system perforation.

A low pH level in a system that contains aluminum and one or more other metals exacerbates electrolysis because putting dissimilar metals in an acidic solution is the recipe for a battery. To demonstrate, try pushing a penny and a nickel into half an orange, about an inch apart. You’ll get a voltage reading across the two coins.

To learn more about the proper care of aluminum radiators and heater cores, obtain a NARSA brochure and caution labels. For more information, call (800) 551-3232.

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