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Working on a PACCAR MX Engine

By on September 15, 2010
RoadKing Mag

I have a newfound respect and appreciation for professional truck technicians.

This comes from my participation in a hands-on engine tear-down and rebuild at Peterbilt’s Training Center in Denton, Texas. It was part of a training session on Paccar’s new heavy duty MX engine, which was launched in January.

The Paccar MX is an in-line 6-cylinder, 4 valves per cylinder, 12.9-liter engine that comes standard with an integral engine compression brake. The engine uses selective catalytic reduction (SCR) in combination with exhaust gas recirculation (EGR).
My training session was a special condensed version of the hands-on engine training all Peterbilt and Kenworth (Paccar divisions) dealer salespeople and technicians are receiving on the new engine.

The first part of my training included disassembling the oil pan, oil pump, stiffener plate and main bearing. If that wasn’t challenging enough, these all had to be reassembled.

I should note that I am not among the most mechanically inclined or gifted. I am happy to report, however, that with occasion guidance of Peterbilt service and training personnel, the engine did get put back together, although it was a couple of bolts short. (They must have fallen inside the engine because they weren’t on the floor. Good thing this engine wasn’t going back into service.) Upon looking over the “rebuilt” engine, one of the service trainers quipped: “Don’t quite your day job.”

The next task was disassembly and reassembly of the valve cover, rocker assembly, high-pressure fuel system, engine brake and pump module. I also managed this — with help — and once again, somehow misplaced a couple of bolts.

It also needs to be pointed out that all this engine work was done with a cleaned up, dry (all fluids removed) engine in an engine lab. The engine was mounted on a stand allowed the engine to be rotated using a cranking mechanism. As I was doing my engine work, I realized even more clearly just how difficult a truck technician’s job is, and how skilled and talented they need to be to properly inspect, maintain and repair vehicles. Unlike working in a clean, temperature-controlled lab – which I did for the training, truck technicians work in real-world conditions under time pressures.

Wearing a lab coat and technician gloves, I remained clean. When’s the last time you saw a technician that didn’t have dirt and grease on his uniform or under his or her fingernails?

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  1. mike prue

    February 3, 2012 at 4:57 pm

    you siad it. i work on mx engines in the real world for a kenworth dealer in omaha. paccar has a good product but they stuffed it between the frame rails and its not a very “clean” engine to begin with, theres so much stuff on it its almost ridiculous. im sure working on an engine in the lab is great for the engineers, but i can say, without too much doubt, that the same engineers who think this is the best thing since sliced bread dont ever work on their invention in the real worl conditions theyve seen fit to subject the techs to. it amazes me at times the gap between the real world and the drawing table. i can say however, the engine itself is a good engine and in my opinion will only get better with time, (as long as those same engineers take heed).

    • Rachel Lex

      July 1, 2016 at 9:37 am

      Hi Mike,

      Quick question for you: I’ve been hearing about technicians struggling with valve adjustments on 2015 or newer PACCAR engines. Have you also had trouble? If so, do you believe there is a tool (already available or one that could be invented) that could alleviate this difficulty?

      Thanks for your time!

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