Repair and Diagnosis: Application and ID
Bolt and Nut Identification
Bolt identification
A large number of the nuts and bolts used on New Range Rover must be discarded after removing or loosening them.
CAUTION: All rear suspension fixings must be replaced whenever they are removed.
An ISO metric bolt or screw made of steel and larger than 6 mm in diameter can be identified by either of the symbols ISO M or M embossed or indented on top of the bolt head.
In addition to marks identifying the manufacturer, the top of the bolt head is also marked with symbols indicating the strength grade, e.g. 8.8; 10.9; 12.9; 14.9. As an alternative, some bolts and screws have the M and strength grade symbol stamped on the flats of the hexagon.
Encapsulated bolts and screws
Encapsulated bolts and screws have a micro-encapsulated locking agent pre-applied to the thread. They are identified by a coloured section which extends 360� around the thread. The locking agent is released and activated by the assembly process and is then chemically cured to provide the locking action.
Unless a specific repair procedure states otherwise, encapsulated bolts may be re-used providing the threads are undamaged and the following procedure is adopted:
^ Remove loose adhesive from the bolt and housing threads.
^ Ensure threads are clean and free of oil and grease.
^ Apply an approved locking agent.
An encapsulated bolt may be replaced with a bolt of equivalent specification provided it is treated with an approved locking agent.
Self-locking bolts and screws
Self-locking bolts and screws, i.e. nylon patched or trilobular thread can be re-used providing resistance can be felt when the locking portion enters the female thread.
Nylon patched bolts and screws have a locking agent pre-applied to the threads. They are identified by the presence of a coloured section of thread which extends for up to 180 degree around the thread.
Trilobular bolts (i.e. Powerlock) have a special thread form which creates a slight interference with the thread of the hole or nut into which it is screwed.
DO NOT re-use self-locking fasteners in critical locations (e.g. engine bearings, flywheel). Always use the correct replacement self-locking nut, bolt or screw.
DO NOT fit non self-locking fasteners in applications where a self-locking nut, bolt or screw is specified.
Nut identification
A nut with an ISO metric thread is marked on one face or on one of the flats of the hexagon with the strength grade symbol 8, 12, or 14. Some nuts with a strength grade 4, 5 or 6 are also marked and some have the metric symbol M on the flat opposite the strength grade marking.
A clock face system is sometimes used as an alternative method of indicating the strength grade. The external chamfers or a face of the nut is marked in a position relative to the appropriate hour mark on a clock face to indicate the strength grade.
A dot is used to locate the 12 o'clock position and a dash to indicate the strength grade. If the grade is above 12, two dots identify the 12 o'clock position.
When tightening a slotted or castellated nut, never loosen it to insert a split pin except where recommended as part of an adjustment. If difficulty is experienced, alternative washers or nuts should be selected, or the washer thickness reduced.
Where bearing pre-load is involved, nuts should be tightened in accordance with special instructions.
Self-locking nuts
Self-locking nuts, i.e. nylon insert or deferred thread nuts can be re-used providing resistance can be felt when the locking portion of the nut passes over the thread of the bolt or stud.
Where self-locking nuts have been removed, it is advisable to replace them with new ones of the same type.