“No Power” 2008 International MaxxForce 7 Diesel Engine – No Turbo Boost
This is what we discovered on our one and only International hybrid school bus equipped with a MaxxForce 7 diesel engine. The complaint was the ever so common “no power” problem so we hooked up the laptop and the diagnostic software and went to work. We found there was zero turbo boost.
Below is the actuator that houses an electric motor to run the wastegate. The ball stud is worn out causing the swivel end to fall off completely.
This is the linkage that was previously attached to the actuator. You can see how it links to the wastegate on the turbo. The turbo has to be removed to change the link end.
After a visual inspection of the charge air hoses and piping one of the techs came across the wastegate linkage that was disconnected totally from the wastegate and the actuator. The linkage had worn out to the point where it came unhooked at the ball stud connection on the waste gate actuator.
The Purpose of the Wastegate
The wastegate regulates maximum turbo boost to protect the turbo and the engine. It accomplishes this by diverting exhaust gas away from the turbine which controls RPMs.
I ordered what was called an actuator kit that came with everything required. It cost just over 1,200 dollars for the kit since none of the parts could be ordered separately. It was unfortunate but it would have taken a lot of time to track down similar ends and linkage combined. The bus was down so the only option was to get the complete assembly.
Once the linkage and actuator was installed back on to the turbocharger the top end could be reassembled. Once the running checks were done we took the bus out for a lengthy road test. There were no problems on the road test so the bus is ready for the road. All said and done the parts were expensive but there’s a valuable school bus that needs to go back to work.
No Longer a Hybrid School Bus
This bus is no longer is a hybrid since the batteries failed twice and the hybrid side was scrapped. So now it’s strictly a diesel engine. The hybrid concept was a great idea but it’s a lot extra components added on to save fuel mileage. The savings in fuel was not significant at all.
The generator was inline with the driveshaft which was cooled by a water pump integral to the hybrid system. The battery pack was air cooled by a blower fan. Unfortunately there wasn’t a battery good enough to sustain a charge under this type of application.
The “go green” program initiated by the BC government was admirable but hybrids are not a popular choice for bus fleets. They are very expensive to buy and you need to find certified techs or train your own techs to work on them.
The Voltage in the battery pack runs at 800 volts so you need special skills to work on this system. We also had issues with our Thomas hybrid and drove it down to Vancouver 4 hours away. The Freightliner dealer there were the closest shop with a certified hybrid tech.
That’s my story and I hope you liked it. Please comment below with your feedback or questions. If you’ve experienced similar problems or own a hybrid I would love to read what you have to say.