School Bus Mechanic Service Call

Almost 2 weeks into the new school year and there has already been a couple of service calls and the maintenance cycle is starting to build. A rare occurrence out of town late in the afternoon was one of our International buses that had a hot running rear wheel and the inability to build air pressure. The clues to what that description signified made diagnosing over the phone very easy.

I said rare which is true how many times this problem has surfaced. As soon as the driver said hot running brake on one rear wheel and no air pressure build up told me that there was either a diaphragm that had blown internally in one of the spring brake pots or the supply air to the spring brake pot was leaking to atmosphere.

So when mustering the 2 guys going out on the service call 30 minutes out of town I told them it sounded like a faulty spring brake pot diaphragm. The mechanic took extra hoses and a caging bolt just in case. The brake pots have to have a caging bolt attached according to the commercial vehicle inspector which is a good thing but you never know what can happen. It’s always good to take extra precautions when going out of town on a call.

I learned a long time ago to take extra parts, tools and an extra set of keys for the bus that’s broken down just in case the keys are misplaced. It’s frustrating when you get there and you can’t do anything until you find the keys. In the end it was in fact a failed spring brake pot diaphragm. The internal spring which is very strong will break and punch a hole in the diaphragm.

We replace the spring brake pots every 5 years with MGM brand since they are the best quality available. Funny thing this bus was on it’s 5th year so the next motor vehicle inspection would have included a spring brake pot replacement on the drive axle. At least this happened in stable weather considering there were 8 kids on board. Our dispatcher contacted another bus to get them home.

As the wheels on our fleet turn the mileage adds up quickly so of course the servicing schedule gets filled up and problems happen. All of the mileages were checked in the summer saving some embarrassing over sights at start up. We generally try and make sure the drivers have their designated bus on the first day for obvious reasons to avoid confusion. This is just one day out of 40 weeks school bus time so there will be more fun stuff to write about in the future.