Diagnosing the Screech on a Silverado LB7 Diesel Engine


Since the belt is relatively new and in decent condition, we just placed it aside to reach the idler pulleys without completely removing the belt. The pulleys can now be loosened and removed via the 14mm bolts. While we had the old pulleys out, we went ahead and spun them in our hand to feel any resistance. Sure enough, one of the pulleys had audible resistance.

Next, we installed the new pulleys. We torqued the 14mm bolts to about 35 ft/lbs. It is pretty as much of a “plug and play” installation as it seems.

After installing the pulleys, reinstall the belt exactly how it was removed. It helps to have a friend put the belt back into place while the other person is holding the tensioner loose on large motors, such as this. In our case, Rob used his muscles to hold the tensioner while we placed the belt on. 


With the belt back on, fire the engine to verify that the diagnosis is complete.

Great! After all of that, the screech is still there! However, it had a slightly different pitch this time. Back to the spraying diagnosis. We tested the AC compressor, all pulleys and the accessory drive belt- all without success. 

We removed the belt once again and quickly spun each pulley by hand to feel any small resistance. Sure enough, the newer alternator pulley had a small squeak, despite it being less than a year old. Fortunately, it was still under warranty! We exchanged the alternator at the local parts store that we originally purchased it from, and installed the new one. We also went ahead and grabbed an accessory drive belt at this time, just in case we needed it.


Time for a quick lunch break and photo opportunity while we waited for the parts to come in.


We couldn’t help but notice this beautiful RX-7 purpose-built track car that was keeping us company during our break. 

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