My brother has a 2012 GMC Sierra that is making a chirping sound when he starts the vehicle and while the engine is running. He stated that he removed the serpentine belt and the A/C belt. He stated when he started the engine it was still making the chirping sound. He also stated that he did a visual on the Hormonic balancer and it wasn't wobbling. He stated he couldn't tell where the chirping is coming from. He stated its in the engine bay area. Can anyone advise what could be wrong, Thanks in advance.

 

Get an empty spray bottle, fill it with water and a bit of dish soap and mix it up. Spray it on the serpentine belt when running. (it won't harm the belt). If it stops making noise, the belt is likely in need of replacement. If not it may well be the tensioner or another item on the system is going bad on your vehicle, which depends on the belt to operate properly.

 

Thanks for the info. He stated that he removed both belts and the chirping noise was still there when he started the engine. Nothing was turning but the crank shaft.

 

Well the chirping sound has stopped but the engine is miss firing now on cylinder # 3. . The injector, spark plug, coil pack, spark plug, and spark plug wire were changed but each time the check engine light came back on and showed a code of 303., Not sure what could be the problem. The truck was running great before the chirping sound and now the miss firing and the truck runs rough. Any suggestion on what I need to check your help is appreciated.

 

Could be a rocker arm causing the chirp, and the misfire.

 

Yes, and should do a compression test on the offending cylinder and the cylinders on each side of it to compare.

 

Thanks for the information on the compression test. We did the test on 1,3,5 and they were all at 170. Number 3 is the one we are still getting the miss fire on and the truck is still running rough.