By Truck Parts & Service Staff
Pressure Sensor Hose & Clamp
Effective April 22, 2008, the coupling hoses and hose clamps used to connect the pressure tubes to the differential pressure sensor on Mack MRU and LEU model chassis equipped with the non-catalyzed diesel particulate filter, were changed to smaller clamps (labeled 1 in Figure 1) and a smaller inside diameter hose (labeled 2 in Figure 1). This was done to eliminate leakage.
Prior to this implementation date, leakage could occur if the clamps were not tightened adequately, but the clamps could be damaged when tightened sufficiently in an attempt to stop the leakage.
If you find leakage at the differential pressure sensor tubes on a chassis manufactured prior to April 22, 2008, replace the existing coupling hose and clamps with the new components: Part No. 83AX968 (hose clamp, maximum diameter 0.63 inch, minimum diameter .38 inch) replaces Part No. 83AX782; Part No. 160AX567F (hose, 3 inches long) replaces Part No. 243AX16.
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, then shut it off.
Exhaust Manifold With Stainless Steel Rings
To provide improved sealing at the exhaust manifold joints, Mack is offering a revised exhaust manifold assembly (Part No. 21113789). It utilizes stainless steel rings at the slip joints.
The revised manifold is available as a complete assembly only, and is to be used if you find exhaust leakage at the slip joints or if any one of the three manifold sections requires replacement.
Note: The revised manifold assembly (Part No. 21113789) consists of the three manifold sections assembled together with stainless steel seal rings at the slip joints, and is ready for installation on the engine. Do not dismantle the sections, as this would result in damage to the stainless steel seal rings and the seal rings are not available separately.
Reman Fuel Injectors Improved
There have been some issues with Caterpillar mechanical unit injectors on models: 3114 ATAAC NA D1 (S/N: 5YL1-Up); 3114 (S/N: 9LL1-Up); 3116 ATTAC D1 (S/N: 2BK1-Up; 7SF1-Up); 3116 (S/N: CSM1-Up; 2FR1-Up; 7HS1-Up; 9Gk1-Up; 7HJ1-Up and 9CJ1-Up); 3116 ATAAC (S/N: 7JL1-Up) and 3116 T (S/N: 9LN1-Up and 9YN1-Up).
The remanufactured mechanical unit injectors now are shipped with the rack in the fuel “off” position in order to eliminate the need to move the fuel rack before installation into the cylinder head.
The fuel rack on the mechanical unit injectors should not be moved without compressing the tappet spring.
The issue is the dragging of the fuel rack and was caused by the process of remanufacturing the cones for the fuel injectors. The remanufactured cones were causing the rack to drag. The cones now are remanufactured in order to prevent the fuel rack from dragging.
The change in the process of remanufacturing the cones for the injectors has caused the cones to have some discoloration. The change in the appearance of the remanufactured cones is normal. The discoloration will not affect the performance of the fuel injectors.
Lube Pump Assembly Instructions
Use the following procedure to assemble the Dana On-Demand design lube pump and related side-gear components on all D170, 190 and D40K models built after June 16, 2008:
- Install the lube pump into the output side gear so that the pump shaft is pointed upward, in the same direction as the teeth end of the side gear, as shown in Figure 2.
- Install the pump locking dowel pin into the hole in the output side-gear hub. Make sure the pin is lined up with the machined slot in the pump body.
- Install the output shaft side-gear bearing cone and press until fully seated. Use proper press tools.
Safety Recalls
The National Highway Traffic Safety Administration (NHTSA) has issued the following recalls:
- More than 350 Bendix T-14 service brake chambers used on some Bendix ADB22X air disc brakes installed on steer axles on some Daimler trucks are being recalled. The lubricant used as an assembly aid for the T-14 service chambers does not evaporate as intended and can migrate between the pushrod base and the rubber diaphragm. This can cause the pushrod base to become misaligned and lodged in the chamber body after a brake application, resulting in the brake not fully releasing.
If a brake on the steer axle remains partially applied, vehicle steering ability and stability can be affected on slippery road surfaces, possibly resulting in a vehicle crash.
- On 238 model year 2008 Sterling 360 trucks, improperly aligned bolt holes on the turbocharger mounting bracket may lead to cracking in the turbocharger housing. Exhaust gases can be released from the crack in the turbocharger housing, which in the worst case, could lead to a fire.
- The bolt holes in the turbocharger bracket where the turbocharger is affixed on 2,957 model year 2008 Mitsubishi Fuso FE83D, FE84D, FE85D and FG84D trucks were manufactured with insufficient clearance. As a result of insufficient clearance between the affixing bolts and the bracket holes, stress is placed on the mounting boss when the bracket is affixed to the turbocharger. In this condition, expansion and contraction of the turbocharger housing mounting boss during normal engine operation may cause thermal fatigue of the turbocharger housing. The turbocharger housing may crack, releasing exhaust gas that could cause a fire.
- 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 properly tightened.
