Vehicle - Friction Modifier Covered Bolt/Nut Usage
No: TSB-07-00-004DATE: April, 2007
MODEL: All Models
PURPOSE
This bulletin contains general instructions to follow when servicing vehicles with friction modifier coated bolts and nuts.
AFFECTED VEHICLES
All models
BACKGROUND INFORMATION
Purpose of Friction Modifier
^ The bolts/nuts coated with friction modifier are used to ensure stable clamping forces necessary to improve the quality of fastener clamping components.
Types of Friction-Modifier-Coated Bolts and Nuts and Their Identification
^ The following types of friction-modifier-coated bolts and nuts are used at present time. They can be identified by the color of paint applied to the surfaces of the bolts and nuts.
General Instructions for Use of Friction-Modifier-Coated Bolts and Nuts
^ Regardless of "reusable" indications in the service manual or other technical literature, bolts and/or nuts with damage, contamination or adhesions of oil/grease or solvents must be replaced with new ones.
NOTE:
NEOTORQUER coated bolts and nuts used in locations identified as reusable are reusable up to about five times. Bolts and nuts coated with any type of friction modifier other than NEOTORQUER should be treated as a non-reusable part.
Storage
^ Frictional coefficient of the friction-modifier-coated surfaces may decrease if they come in contact with oil/grease or solvents. Storing them in nylon bags is recommended to keep them from contamination.
^ Do not use the bolts or nuts if they have damage, contamination or adhesions of oil/grease or solvents.
Tightening
^ Tighten the friction-modifier-coated bolts/nuts to the specified torque.
^ Do not tighten with an impact wrench.
^ The tightening speed should be constant at a rate of approximately ten to thirty revolutions per minute (60 to 180 degrees per second).
^ Some friction-modifier-coated bolts require application of oil before being tightened (example: crankshaft pulley bolts). Be sure to follow the instructions in the service manual.
Tightening
The coefficient of friction of the friction-modifier-coated bolts/nuts depends on the speed at which they are tightened. The friction coefficient increases as the tightening speed increases but becomes saturated at and above a rate of five revolutions per minute (30 degrees per second).
The tightening torque of a friction-modifier-coated bolt/nut is measured by turning it in the retightening direction. The measured value is around 20% lower (at maximum) than the value that should be indicated although there is no decrease in clamping force (axial tension) of the bolt/nut.
Therefore, a necessary clamping force (axial tension) is maintained even if the measurement is up to 20% lower than the specified value and the inspection result should be regarded as satisfactory. However, if the measurement is more than 20% lower than the specified value, the bolt/nut may have lost the necessary level of clamping force (axial tension) and the bolt/nut must be replaced with a new one and tightened to the specified torque.