Ed Evans Speaks Out

Grease oil, thread lock fluid or nothing? Ed advises

Grease, oil, thread lock fluid or nothing at all – those are the options when bolting parts back onto our Land Rovers. It’s wise to read what the Land Rover manual says when rebuilding or attaching any component. For instance, if thread lock is stipulated, it must be used to prevent the fastener becoming loose through vibration, or expansion and contraction of materials during temperature changes as components warm up and cool down. Locking nuts and locking washers are not an alternative to the specified thread locking fluid.

Thread locking fluid (before it sets) affects the friction between the two threaded components, and that in turn affects the tightening torque. So it’s important to use the specified thread lock fluid with the specified tightening torque. Grease or oil on threads can also affect the tightening torque, which is why it’s inadvisable to use anti-seize and other lubricants on any bolts or nuts that have a specified torque. For example, old bolts on independent suspension models can seize or rust in, but applying protective grease when fitting new ones can lead to the torque wrench not registering the actual tightness, causing a new bolt to be overtightened and shear.

Bolt threads are often lubricated to prevent corrosion, so that next time the component is removed, the bolt or nut turns easily. Alternatively a dab of grease under a bolt head or its washer prior to fitting will prevent moisture getting down the thread without affecting the feel on the spanner during tightening. Where bolt threads protrude from a component or nut, a smear of grease on the exposed thread helps seal it and prevent rusting – it’s usually rusting of this exposed thread that causes stiffness or shearing when releasing a correctly-tightened bolt.

We all have our own ideas, but it’s important to consider the potential consequences remembering that, at their contact face, screw threads are simply a helical wedge, held only by friction.