GM-51952 compression gauge adapter provides access through the glow plug bore in order to test compression and cylinder leak-down on 2011-newer 5.2L 4HK1 diesel engines. GM-51952 also allows compressed air to be put into the cylinder to hold the valves shut for valve spring or valve stem seal service without removing the cylinder head. Once the glow plug is removed, the adapter body of GM-51952 is installed in place of the glow plug.
The Schrader adapter is installed to the adapter body of GM-51952, allowing connection to the GM-26999 compression gauge for testing compression. The Schrader adapter is removed and the air line from GM-35667-A cylinder leak-down tester is connected to determine the source of any leak found. If valve spring or seal service is required, an air line can be attached to the adapter body to allow compressed air into the cylinder to hold the valves against the cylinder head.