Diagnose This! Three puzzles, one winner

Diagnose This! is a new regular feature in Truck Parts & Service. Below are the answers to the January, February and March Diagnose This! puzzles. If you have a service scenario you would like to submit for consideration in an upcoming issue or to submit an answer for a Diagnose This! puzzle, please e-mail Dsmith@rrpub.com. All three Diagnose This! puzzles were submitted by ASE master technician and owner of Fleet Guardian, Damon Russell.

Bearing Failure – January, Page 63
Problem: Transmission output bearing failure occurs shortly after truck was repaired for an engine shutdown issue while in PTO mode. Truck has a split-shaft PTO before the tandem and operates an air compressor which requires the truck to operate in ninth gear for PTO operation.

Solution: The Spicer transmission rear bearing has to be set up. If the bearing is loose it has to be re-established correctly. If you just tighten the nut the rear bearing will scald. I suppose the tone ring got to slipping and they tightened the nut and replaced the sensor.

Winner: Dave Mason, truck service manager, Midway Motors Supercenter, McPherson, Kan.

Dead Miss Detective – February, Page 47
Problem: Customer complained of a sudden weak engine brake and odd engine sound on a Caterpillar C12 with 690,000 miles. The truck clearly had a dead miss.

Solution: Cat advised service personnel through a Truck Service Bulletin to replace the followers if the injector experienced a hard seizure (i.e. plunger stuck in the down position). While this truck did not have a seized injector, it was determined to be binding and was the cause of the follower failure. The follower simply experienced excessive load and the follower trunnion suffered an early demise.

Winner: There were no correct submissions.

Knock, Knock – March 2008, Page 55
Problem: A 2005 International 4300 developed a sudden moderate engine knock at all engine speeds. Noise was originating from the air compressor area. The air compressor and power steering pumps were removed from the engine and the engine was run for verification. The knock persisted.

Solution: This engine saw a prior air compressor seizure that was repaired under OEM warranty early in its life. The compressor locked after shutdown and the engine was locked on a restart attempt. The crankshaft gear had suffered the effects of the start attempt, a few teeth were slightly displaced and this damage was undetected when the compressor was replaced. The engine continued to run for several thousand miles afterward until the displaced tooth broke away from the gear entirely, which occurred at the weakest point in the gear – the alignment notch. The noise immediately followed.

Winner: There were no correct submissions.

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