Diagnosing the Screech on a Silverado LB7 Diesel Engine

by Karla Pestotnik

Any car can eventually get a pesky squeak coming from the drive belt area under the hood. For many 1999-2007 General Motors V8s, this has become an infamous issue. However, this common issue is often more than just a belt change; it can be a little bit more complicated. In our case with the LB7 diesel Silverado, it was multiple sources contributing to some head-scratching pondering. Since this is the dedicated tow vehicle for the Karla Pestotnik Racing team and a big event is coming soon, we needed to get to work to diagnose and fix the tow rig.

To get started, we took the truck to our friend, Rob Choo from Chewerks. Most people think of fast racecars and alignments when they think of Chewerks in City of Industry- not beefy diesel trucks. This isn’t a typical job for the Chewerks shop, but we know that he can fix almost anything. Let’s get started!

First things first- finding the source of the squeak. Since the accessory drive belt was replaced a year ago, we knew that it was more than just that. Rob brings out the trusty WD-40 to easily find the source.

By spraying each pulley one at a time, the source can be found easily. If a pulley is sprayed and the screech stops, you have found the winner! Rob had a feeling that one of the drive belt idler pulleys was the issue, so we ordered both ahead of time. Since they are relatively inexpensive, we went ahead and purchased both to replace at the same time. The last thing that we want to have happen is to just replace the bad pulley, and then a few months later the other one fails as well. While we were already in there, it was the perfect opportunity to do both at the same time. Sure enough, the squeak quieted briefly after spraying them.

Sure enough, one of the two black idler pulleys was a source of the squeaking. Don't mind the WD-40 overspray.

Diagnosing the Screech on a Silverado LB7 Diesel Engine