Loose Exhaust System Fasteners

The exhaust system fasteners may be loose or damaged on some 2022 Silverado 4500HD/5500HD/6500HD trucks and 2023 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD trucks equipped with the 6.6L Duramax diesel engine (RPO L5D, L5P). The loose or damaged fasteners may be due to incorrect bolts being used on a prior repair.

The fasteners used for the exhaust manifolds, turbocharger adapter and Exhaust Gas Recirculation (EGR) valve require a locking feature to prevent the bolts from coming loose. The following two different locking features were used in the L5P engine during the 2023 model year and in the L5D engine during the 2022 model year.

• The Powerlok fastener has a tri-lobular design with a locking feature integrated into the bolt. The tapped hole in each exhaust component does not have a locking feature. The Powerlock bolts used in production are grey. A service bolt may be either grey or black. (Fig. 1)

 

Fig. 1

 

• The standard-style bolts do not have a locking feature. Instead, the tapped hole has a 30-degree Ramp Angle Thread (RAT) that acts as the locking feature. The standard bolts are black with a dished head. (Fig. 2)

 

Fig. 2

 

TIP: Over its time in use, the visible color of the bolt may change. (Fig. 3) Use a pick or pocket screwdriver to determine if a bolt head is flat or dished.

 

Fig. 3

 

The correct bolt and threaded component must be matched together to properly secure each component. If the threaded component is matched with the incorrect fastener, the fastener may become loose or damage may occur to the threads during installation or removal.

The first design exhaust manifolds, turbocharger adapters and EGR valves are standard threaded hole. The second design components are 30-degree Ramp Angle Thread. Second design components will back service to the 2017 model year for the L5P engine and the 2019 model year for the L5D engine. Keep in mind that vehicles originally built with standard threaded hole components may have been serviced with 30-degree RAT components.

Exhaust Manifolds

 

Fig. 4

 

First design – Use only grey Powerlock bolt

Second design – Use only black standard bolt

The torque specification is the same for the standard and Powerlok bolts at the exhaust manifold.

Turbocharger Adapter

 

Fig. 5

 

First design – Use only grey Powerlock bolt

Second design – Use only black standard bolt

The torque specification is the same for the standard and Powerlok bolts at the turbocharger adapter.

EGR Valve

 

Fig. 6

 

First design – Use only grey Powerlock bolt

Second design – Use only black standard bolt

The torque specification for the standard bolt is 23 lb.-ft., 31 NM, and for the Powerlok bolt is 30 lb.-ft., 40 NM, at the EGR valve.

Refer to Bulletin #24-NA-253 for more details, including part numbers.

Thanks to Mike Buckel