Series Land Rovers are basic in their construction. Diagnosing faults, however, may require a level of sophistication that is best acquired by experience. This article describes the nature and background of a specific problem. We follow a path in search of a diagnostic solution - a sort of murder mystery without the murder.
So let us now describe the scene for our hypothetical Series Land Rover. The vehicle is a 1961 LWB Series IIA petrol station wagon with standard wheels and Rover front axle but fitted with Fairy freewheel hubs and a steering damper.
The problem is that a noise is heard from the front of the vehicle when in motion. The repetitive noise is usually only heard when travelling at slow speed; less than 15mph. It is clearly related to speed of the vehicle and is best described as a loud click that increases in frequency as vehicle speed increases. The sound seems to be to the left of centre from the drivers perspective. There are no other observed vehicle problems related to either steering or braking. Any ideas already?
As with many vehicle faults
it is good practise to investigate as much as possible into what situations cause the fault to present itself. So in this case it is noticed that moving at very slow speed, the clicks seem to be at the rate of one per wheel rotation. Also, there is no observed difference to the click rate when the clutch pedal is depressed. Neither is there any change to the click rate when the freewheel hubs are disconnected.
Well we should always go for the most obvious causes first. So we suspect a wheel problem. How about jacking up the wheel and rotating it by hand slowly, whilst inspecting the tyre tread for any small object trapped in it? This could cause a sound closely related to wheel rotation. OK, inspection done and there is no object imbedded in the tread. Neither is the wall of the tyre bulging or damaged anywhere due to a localised tyre weakness. So now we rotate the wheel forwards and backwards and listen for any sounds. Doing this, the result is that no sound is heard either rotating the wheel in either direction. For added information, there is no detectable movement when the wheel is rocked from side-to-side or from top-to-bottom. So good evidence for no slack wheel bearings or worn steering ball joints.
Part of the road testing earlier discovered that the sound was present whether the freewheeling hubs were engaged or not. But we need to be sure that the hubs are working as they should and do actually disengage when required.
Now, we can check if the freewheel hub is really disengaging since the wheel is off the ground. The result is that turning the wheel with the hub disengaged fails to rotate the propshaft. So the LHS freewheel hub is working correctly
So, that was unexpected. OK, so as commented upon in last month's Series Land Rover fault diagnosis basics article; lets try the process of substitution. In a previous homepage article the case for hoarding used Series Land Rover parts was advocated. So lets substitute the LHS Fairy hub for the original drive member and test again. This should eliminate an internal fault in the Fairy hub as the cause if the noise. The result; exactly the same sounds when driven under the same circumstances. So we can rule out an internal fault of the freewheeling hub as the cause.
We didn't find any obvious problem with the wheel bearings. So the only other rotating part is the universal joint in the front LHS halfshaft. But this should have been rendered motionless when tested with the freewheel hub disengaged (the clicking was still heard) and we have shown that the Fairy hub is functioning correctly.
OK, well we seem to have eliminated the wheel bearings, Fairy hub and universal joint.
Lets remove the propshaft and test again incase the source of the clicking sound was really more central than it appears to be. With the propshaft removed the test drive reveals the same results as before.
So, we have a dilemma. Only three moving parts and non of them apparently faulty. But we know from Series Land Rover fault diagnosis basics that complications towards achieving a correct diagnosis can exist. In this case we should, and did, initially suspect the wheel bearings. But the test of rotating the elevated wheel failed to support the idea that the wheel bearings are the cause. However, the road test put the bearings under far more stress and so maybe they should be re-examined as the cause.
Removing the complete wheel hub and rotating the bearings by hand under light pressure reveals an unevenness at one particular point in rotation of the outer bearing. This could be the clicking under load that was heard. We need to change the bearings. Once changed it was noticed that there was no more unevenness when the bearings were rotated by hand.
Road testing the vehicle resulted in silent travel - problem solved.
So the lesson to be learned here is that although we tested all suspected parts, we did not test them under the conditions they experienced when on the road.
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