Fault Phenomenon: Caterpillar 938 wheel loader a tire frequently loses pressure; inspection reveals air leak at the valve stem.

Troubleshooting Process:
– Checked valve core: valve core rubber gasket aged or damaged.
– Checked valve stem: metal valve stem root cracked.
– Checked wheel rim: rim valve hole corroded.
– Checked foreign objects: valve stem damaged by stone impact.

Root Cause: The tire valve stem rubber aged and cracked, or the metal valve stem developed a fatigue crack due to vibration, causing air leakage.

Required Parts: Replace tire valve stem and valve core.