Mechanic Repairs In The School Bus Garage

Various School Bus Repair Photos From The Bus Garage

Every day mechanic duties change and this video is a small example of what goes on in our school bus garage. The diesel mechanic jobs involve the ISC Cummins and Mercedes MBE 900 diesel engines. These 2 engines are the oldest in our fleet and have given us some trouble because of age and mileage but we always repaired them as needed with the proper tools and software.

There are also small repairs which include oil and coolant leaks, Air brake system leaks and periodic brake jobs. Electrical problems are consistent with multiplex wiring on the newer models that use modules to run lights, motors and accessories.

One important tool that every diesel mechanic must have is the appropriate software for troubleshooting engine codes and performing static and running tests to find out what diesel component is failing or has failed completely.

Many times the engine code will tell the mechanic that the EGR exhaust gas recirculation valve is not in the right position. That's one of the easiest problems to have since 9 times out of 10 the EGR is sticking because of a heavy soot buildup.

Multiplex Wiring

Multiplex wiring is a common problem in the electrical department. Using the AccessFreightliner website is essential. If you go into the "PartsPro" section and enter the last 6 digits of the vehicle ID you can find an excellent schematic of the modules and other wiring systems. Doing a "search" and entering a keyword like "ABS" for example will bring up a schematic for the antilock brake system.

If you don't have a user and password for accessfreightliner phone the dealer and ask them about getting one. I'm not sure what the rules are but it's worth a try especially if you own Freightliner trucks or buses. In our case the buses are the C2 conventional saf-t-liner. They came to our fleet in 2005. Before that year the freightliner school bus was made out of the FS65 medium duty truck chassis.

The EOS Electronic Oil Separator

The video shows an EOS (electrostatic oil separator). This piece is part of the valve cover and separates the crankcase gases from the liquid which is funneled back into the crankcase while the vapors are routed back into the intake. This component costs 800.00 if it comes time replace it. If you get an EOS engine code you're stuck with ordering a new one. That's the downfall of getting into emission controlled engines. You need a healthy budget to repair them.

The Cummins VGT

The Cummins B 6.7 liter diesel engines in our fleet are great runners but if you have to replace the turbocharger in our case there was oil leakage into the intake side (compressor wheel). It cost 2400.00 for the VGT variable geometry turbocharger reman and a fair bit of labor to do the re and re.

The VGT is a great design and not only changes it's angle to act as an exhaust brake but also helps the engine do a regen by blocking the exhaust flow to develop engine heat for a faster and more efficient regen. That's all I want to say for now ...thanks for the visit and please leave a comment below. I would like to hear some feedback from you.

School Bus Garage Photos

I've been taking photos in our school bus garage since 2005 and didn't want them to go to waste so here is a short video with RANDOM pics. There's everything from instant snow chains to engine repair.




 2005...I remember it well, we still had mechanical diesel engines in the fleet. They were semi-retired as spare buses and just this year we are auctioning off our last mechanical engine equipped units (Cat 3116 models). The 3116 Cat gave us pretty good service but nothing stellar to speak of.

 I believe there were 4 engine rebuilds because of the exhaust valve dropping at a very bad moment. Usually the high heat pulling full load would cause the mishap. It was a lot of work since the block was solid without removable piston liners. The entire engine had to be removed from the chassis, stripped down and rebuilt from scratch. The rebuilt head ran about 1500 dollars Canadian, if the cylinder wall was scored then the block was sent to a machine shop which MUST know the repair steps when boring and re-sleeving these engines.

There is a special jig to be used to secure the block so it doesn't warp during the re-bore. It adds up to about 5K labor and parts. This of course is far less than buying a long block. The top end on the 3116 was the weakest part of the engine so valve adjustment is crucial. The engine operating temperature is a factor as well so they need TLC or they start to heat up over 200 degrees.

The engine fan in the pusher school buses were transversely mounted so it was hard to keep the temperature down especially in warmer months. We disabled the shutters (opened permanently) and installed an over riding dash switch to turn the engine fan on full which took some horsepower out of the engine. In the video you'll see the coolant sensor that runs the hydraulic fan solenoid.

When you unhook the sensor wire the fan runs full on. The dash switch we installed for the driver just caused a break in the circuit. It should also be mentioned that the cooling system also had to cool the transmission oil which could get up to 200 degrees. The radiator mounted sideways at the back of the bus had a hard time cooling especially when the bus was in 3rd gear with a full load climbing a hill in 80 degree weather. Thanks for viewing this post and I hope you liked the video.