Timing Belt Tensioner: Testing and Inspection

AUTO-TENSIONER CHECK

OPERATION CHECK
1. Turn OFF the engine, then check to see that the drive belt is not protruding from the pulley width of the auto-tensioner.
2. Remove the drive belt.





3. Securely insert the spindle handle or ratchet handle at a 12.7 mm (1/2-inch) angle into the jig hole of the auto tensioner. Turn the auto-tensioner to the left and right to check and see that there is no binding.
4. If there are any problems in the procedure 1 or 3, replace the auto-tensioner.
5. Install the drive belt.

FUNCTION CHECK
You can verify if the auto-tensioner is defective or not by checking the drive belt tension.

When using scan tool MB991958

Required Special Tools:
^ MB991668: Belt Tension Meter Set
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: V.C.I.
^ MB991910: M.U.T.-III Main Harness A

1. Check the drive belt tension.
2. Measure the drive belt tension vibration frequency by the following procedures:





CAUTION: To prevent damage to scan tool M13991824, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool M13991824.
(1) Connect special tool MB991668 to scan tool MB991824.
(2) Connect scan tool MB991910 to scan tool MB991824.
(3) Connect scan tool MB991910 to the data link connector.
(4) Turn the ignition switch to the "ON" position and select "Belt Tension" from the scan tool menu.

CAUTION:
^ The temperature of the surface of the belt should be as close to normal operating temperature as possible.
^ Do not allow any contaminants such as water or oil to get onto the microphone.
^ If strong gusts of wind blow against the microphone or if there are any loud sources of noise nearby, the values measured by the microphone may not correspond to actual values.
^ If the microphone is touching the belt while the measurement is being made, the values measured by the microphone may not correspond to actual values.
^ Do not take the measurement while the vehicle's engine is running.





(5) Hold special tool MB991668 to the middle of the drive belt between the pulleys (at the place indicated by arrow), approximately 10 -20 mm (0.40 -0.78 inch) away from the rear surface of the belt so that it is perpendicular to the belt (within ± 15 degrees).
(6) Gently tap the middle of the belt between the pulleys (the place indicated by the arrow) with your finger as shown in the illustration, and measure that the vibration frequency of the belt is within the standard value.
Standard value: 120 -154 Hz

3. If not within the standard value, replace the auto-tensioner.

When using a tension gauge





1. Check the drive belt tension.
2. Use a belt tension gauge in the middle of the belt between the pulleys (at the place indicated by the arrow) to measure that the belt tension is within the standard value.
Standard value: 340-562 N

3. If not within the standard value, replace the auto-tensioner.