1. Manual Feeling Method
Try turning the bolt with an appropriate wrench. If it turns easily, it may be loose; if it requires more force, it may be tight. This method relies on experience, and beginners may find it difficult to judge accurately.
2. Torque Wrench Method
Set the wrench to the standard torque value. If it turns without reaching the set value, it is loose. Refer to the repair manual; the operation is more complex but highly accurate.
3. Marking and Observation Method
Check if the marking line on the bolt head is aligned with the connected part. If they are misaligned, it may be loose. However, not all bolts are marked.
4. Sound Judgment Method
A sharp, short sound when tightening is normal. A dull sound or noise may indicate looseness. This method requires a quiet environment and is easily disturbed.
5. Professional Testing Method
Strain Gauge Method: Place it on the thread to monitor changes in preload. A sudden decrease indicates looseness. Ultrasonic method: Preload is detected by changes in sound velocity. It has high accuracy but requires specialized equipment.
