This particular school bus had to be towed in because it quit on the road an hour out of town. The diesel engine is a 2011 DT MaxxForce which uses high pressure oil to operate the electronic injectors controlled by the engine computer. The problem we found was loose injector hold downs with faulty sealing washers between the injectors and sleeves where the injectors sit in the cylinder head.
The sleeve is brass and press fits into the cylinder head to accommodate the lower section of each injector. Once the injectors became loose excess fuel got into the combustion chambers and the engine could not run properly. The first step was to remove the valve cover and doghouse from the inside of the cab. We borrowed the tools from our local international dealer. The relationship between us and the dealer is friendly and pays off if we need something like a specialty tool which would normally take weeks.
As described in the video the sleeves are threaded with a tap and removed by threading in an adapter that hooks onto a slide hammer. We found the three cylinders under the fire wall very difficult to access so pulling the head was not an option and decided to clean up the seats on cylinders 4, 5, and 6 instead of replacing them. They looked good once cleaned up so we did not hesitate to carry on with the injector installation.
The new set of injectors come with a new sealing washer and o-rings so all it took was to carefully slide them into the bore of the head and torque the injector hold downs. We took extra precautions and added an extra 5 ft. lbs. to the torque specifications 35 ft. lbs. along with some medium strength loctite to secure the hold down bolt even more. Loctite is a fluid that is applied to the threads of a fastener and once it sets up locks the mating threads securely but the fasteners are removable for the next time.
Since this engine has been reassembled it’s running fine after the fuel system was recalibrated using the engine software and the excess fuel was burned out of the exhaust system. I had thoughts of the fire department showing up due to the clouds of smoke coming out of this bus and wouldn’t you know it I heard sirens coming down the road. The emergency vehicles kept going thankfully…. on their way to a real fire. This is another job out the door and I can see a lot more work coming with these MaxxForce diesel engines.