Under the Hood – April 2008

Interference Between Hood Spring & Charge Air Cooler Hose
On Mack CTP, CHN and CT models manufactured before April 16, 2007, there may be an interference condition between the hood assist spring and the coupling hose on the charge air cooler inlet. When the hood is closed and the vehicle is in operation, spring oscillations result in a wear mark and an eventual hole being worn into the coupling hose, allowing unfiltered air to enter the air intake system.

To correct this condition, a replacement hood spring (Part No. 57QL262BM) is available. (See Figure 1.) If you see a wear mark in the charge air cooler inlet side coupling hose, replace the existing hood assist springs on both sides of the chassis with the new springs. The hood assist springs must be replaced in pairs.

Saftey Recall
The National Highway Traffic Safety Administration has issued the following recall:

On certain 2006 to 2008 Mack CHN, CL, CT, CTP, CV, CXN, CXP and CXU truck models and certain 2007 to 2008 Volvo VHD, VNL, VNM and VT truck models equipped with an SAF Holland Simplex fifth wheel, the lever arm pivot bolt may have been over-tightened. An over-tightened pivot bolt can distort the pivot bolt spacer sleeve, which may prevent the fifth wheel latch jaw from closing and latching securely around the trailer king pin.

The pivot bolt could become loose without the driver’s knowledge. The driver could drive away and the trailer could become disengaged. To fix the problem, replace the pivot bolt and sleeve with a hex head shoulder bolt and washer.

Tips To Prolong Lighting
Grote offers the following tips for prolonging equipment lighting:

Don’t Pierce The Insulation
When troubleshooting lighting complaints, never pierce the wire insulation because wicking can occur, which causes moisture to travel along the wire strands and corrode critical connections. This is called salt creep.

The company recommends that if you are unable to avoid probing a harness or wire, you should make sure that the puncture is sealed properly. Testing should occur at each termination point along the main, rear sill, jumpers, pigtails and lamp itself so that only the damaged extension area is replaced.

Check Discarded Lamps
Grote recommends that when solving lamp problems, take the time to identify the true cause of the complaint to avoid simply fixing a symptom of a greater problem.

First, test the lamp with either a meter, power supply or battery. Next, open the lens and examine the bulb for clues as to why the lamp failed.

A bulb with stretched or broken filaments may have been subjected to heavy vibration. A yellow, white or blue glaze on the bulb indicates a rupture in the bulb glass envelope and a possible leak. A dark, metallic finish indicates old age while a black, sooty bulb indicates a poor seal.

Improper Ground Connections
Improper ground connections are major causes of lamp failure, especially when the trailer is used for a ground. When lamps are grounded through the lamp housing, make sure there is a clean connection. A fifth wheel ground strap may be used for added protection on the chassis ground system, according to the company.