Under the Hood – August 20071

Camshaft Inspection
Hendrickson has developed the following maintenance procedure for inspecting the camshaft and camshaft bushings (or camshaft and cam tube on cam tube system models).

• On all except cam tube system models, check the camshaft axial end play. The total movement should not exceed 1/16″.

• On all models, check for radial play between the camshaft and camshaft bushings. Use a dial indicator rigidly secured to the axle or suspension beam to measure the up and down movement of the camshaft. (See Figure 1.)

The company said that testing shows that radial end play up to .06″ has no significant adverse effect on brake performance.

If you perform a routine inspection without replacing brake shoes or linings and find less than .06″ of radial end play, you do not need to replace the camshaft bushings (or the cam tube assembly).

But, if radial end play is more than .06″, the bushings (or cam tube assembly) should be replaced and the camshaft should be inspected for signs of journal wear, corrosion and cracks.

• On all except cam tube system models, inspect the camshaft for cracks, excessive wear or corrosion.

• On all models, check the S-cam head for damage or excessive wear.
• If camshaft or camshaft bushing replacement is not necessary, continue brake service.

False Reporting Of High Temperature
On certain Mack CV model chassis equipped with an Allison automatic transmission, the vehicle electronic control unit (VECU) might incorrectly detect a transmission oil temperature that is above normal.

Should this condition occur, proceed as follows. Using V-MAC Online, upgrade the VECU software to step 12A. Download the software and the OEM datafile.

Using V-MAC Dealer Programming software, read and save customer data. Using V-MAC Dealer Programming software, reflash the VECU per the instructions outlined in the V-MAC Support Software User’s Guide, 8-353.

Reprogram the VECU and restore customer data using the V-MAC Dealer Programming software per the instructions outlined in the same user’s guide.

Calibrate the throttle pedal. The throttle pedal can be recalled manually by slowly depressing, and then releasing the pedal three times. The throttle pedal also can be recalibrated by using VCADS Software. Clear any fault code and then perform a short road test.

Transmission Fluid Change
Mack Trucks has announced that effective December 12, 2005, DEXRON III is the factory fill for the power steering system on all CXP, CXN and CHN model chassis. Chassis using the new fill in the power steering system can be identified by the label affixed to the power steering reservoir.

Tube Installation Procedure
Caterpillar has released the following installation procedure for its 235-1448 Tube AS in its C11 and C13 engine models:

• First install the Tube As into the oil filter base. This allows the correct alignment of the tube to the bore in the oil filter base.

• Tighten the bolts at the base of the tube to 21+/-5 lb.-ft.

Note: Oil leaks may occur if the tube is not reinstalled properly after the initial failure.

Cylinder Head Part Numbers
A revised inlet valve seat insert was introduced into OEM cylinder head production during January 2005, and revised inlet valves were introduced during June and July 2005.

The cylinder head and valve assembly part numbers are to be used for field replacements that fall within the following guidelines:

• Use a remanufactured cylinder head and valve if available.

• If a remanufactured cylinder head and valve assembly are not available, use a new OEM cylinder head and valve assembly instead.
• Make sure not to use a cylinder head that does not include the valves and related components.

Mack ASET and AMI engines do not require the revised inlet valve seat inserts or the revised inlet valves. Changes were made to the ASET, AI and AMI production and OEM cylinder heads for standardization purposes only.

EGR Cooler Hose
According to Mack, EGR cooler internal leakage in which exhaust gases have contaminated the engine coolant can result in damage to the liner inside the EGR cooler coolant outlet hose in vehicles with Mack ASET-AC engines.

This is the 90 degree hose located at the front of the cooler that is connected to the coolant return tube at the front right corner of the engine.

To avoid subsequent failure of the hose, the hose must be replaced whenever the EGR cooler is replaced.

Retrofitting Cam Enclosure
The following procedure should be used to retrofit cam enclosure manual purge plugs to pressure relief valves on Meritor trailer axles.

• Check to ensure that the snap ring is installed correctly into the camshaft groove next to the slack adjuster. The snap ring may either be tight or free to rotate in the groove depending on the slack adjuster position on the S-cam.

• Remove the pipe plug from the cam enclosure.
• Install the adapter. First hand-tighten it into the threaded hole in the cam enclosure. Then use a wrench to tighten it to 36 lb.-in.
• Install the relief valve. First hand-tighten the relief valve into the adapter. Then use a wrench to tighten it to 36 lb.-in.
• Apply grease to the grease fitting at the cam bushing located at the brake spider until grease purges from the relief valve. Apply grease to the grease fitting at the cam bushing located at the slack adjuster end until grease purges from the relief valve.

Manually Checking Tire Pressure
Hendrickson recommends always disconnecting the tire hose from the tee fitting when manually checking the tire inflation pressure on the company’s TIREMAAX-equipped suspensions. Also, check the tire pressure at the hose end.

When the manual pressure check is complete, reattach and tighten the tire hose to the tee fitting. Do not over-tighten with excessive force.

Check valves in the tire hoses help prevent air loss when a tire hose is disconnected. However, when the system is powered, air loss may occur at the tee fitting. In this case, a blink code will occur if the tire hose is disconnected during a system tire pressure check.

Improved Software Now Used
Caterpillar has announced that the C9 powered RV and fire trucks with 400 hp engine ratings have experienced black smoke occurring both at start-up and on acceleration and complaints about surges that occur around 1200 rpm to 1300 rpm when the vehicle is in cruise.

The company said that there are 213-14 logged faults that cannot be solved by troubleshooting.

The company has introduced new software to reduce the amount of black smoke during start-up and operation. The software also addresses the elevated idle surge, the driving surge and the logged faults.

The software part numbers are 290-9008 engine ratings electronic software and 289-1223 engine ratings electronic software.

Canceled Service Bulletins
Mack Trucks has received complaints about the copper coated exhaust manifold nut (Part No. 189AM2) loosening in service when used with the 616GC279AM exhaust manifold stud on ASET AC engines.

Because of these complaints, Mack has requested that the information released in service bulletins SB 214-029 dated June 6, 2006 and SB 214-039 dated June 6, 2006 only be used in cases where the exhaust manifold studs have failed and must be replaced.

Proactive replacement of the exhaust manifold studs without a failure is not recommended until Volvo Powertrain Engineering has released a new nut that will retain the torque applied at installation.

The company has cancelled the two service bulletins and once a new nut is released, will disperse new service bulletins with updated bulletin numbers.

Replacing ECUs
Unlike previous generations of electronic control units (ECU) where antilock braking system (ABS) units could be switched-out, Bendix EC-60 Advanced ECUs are vehicle specific. Because the company customizes the stability system for the actual vehicle configuration and its sensors, the VIN is required to order replacement ECUs.

Bendix Advanced ABS ECUs intervene based on feedback from expected sensor locations and orientations. Install sensors in their original position and orientation on the vehicle, and recalibrate the sensors after related maintenance work.

Maintenance procedures that require recalibration are steering wheel replacement, steering angle sensor or yaw rate/lateral acceleration sensor replacement, any maintenance that involves opening the connector hub from the steering angle sensor to the column, maintenance or repair work on the steering linkage, steering gear or other related mechanism replacement, wheel alignment or wheel track adjustment and accident repairs.