Thomas School Bus Front Brake Replacement - Problems

Mechanics Hub - June 6, 2014
This is a brake job that has not gone well. It should have been a simple 2 to 3 hour job but everything has gone south as the saying goes. Every time we make a change with linings or machined brake drums the problem accelerates. We have replaced the linings 2 times and machined both the drums and linings.

The problem started off with a squeal which was a piercing noise that you could hear far away. So the elementary step to take is to replace the drums and linings. The drums were badly glazed and scored from years of use. There was lots of lining left but since it was 5 years old we decided to replace the whole package.

Watch the video below and I will show you what we are dealing with.

I put the cart before the horse with details on this job. The video showed you the physical set up of our brake system and this is round two with trying to solve the problem with the brakes pulling and chattering after the first brake shoe and drum replacement. The shoes we are using now are designed to resist brake squeal and pulling and any other condition possible.

The shoes we are going to install are an extra $50.00 a side so I'm hoping it will correct the problem. This bus is a handicap unit so it does a lot of in town routes. The brakes are usually not worked hard enough. One of my suggestions to the driver was to heat the brakes up as soon as possible. In the past I've done this with squealing / pulling brakes since they are supposed to work more efficiently when they are up to a certain temperature. The driver came back and he told me the problem just got worse.

Update After Recording This Video

Since this video was made the new (second set) of brake shoes are creating an annoying howl and the driver says it's embarrassing to operate the bus. He is using a spare bus right now and we have decided to machine the drums again (take off .010) and machine the shoe linings as well. I hope this fixes the problem. I will be posting an update when we see the results.

It's not every day this problem occurs. Most of the brake parts we use and other shops as well are off shore. That's reality in the transportation world. I have never seen this much trouble with a simple brake job. I'm just glad this isn't a retail job because the customer would be screaming down my throat right now. It happens and my best guess on what the problem could be is inferior parts since different and new conditions happened that did not exist before.

If you've had this problem before in your shop please comment so I can see that I'm not the only one who has had this experience. It's part of the trade to have road blocks and head scratching moments. The best part is when the problem gets fixed and it goes down as more experience and something you can share with others.