Saturday, December 27, 2014

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.

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