Series Land Rovers have a relatively simple mechanical design. Diagnosis of problems should therefore be more easily accomplished. But there are many ways in which the path to a correct diagnosis may be obstructed. This homepage article attempts to provide a framework for a more effective diagnostic process. It encourages lateral thinking in the process of finding the cause(s) of a problem. Later articles will focus upon specific problems and their diagnosis; presented in the form of logical exercises.
Before trying to diagnosis the cause of a particular problem, there are few fundamental truths that need to be uppermost in our mind:
1. As all doctors are aware - not all symptoms are relevant to the diagnosis of a particular illness. We need to be aware that some of the sounds, vehicle behaviours or mechanical issues may not all be relevant to the particular problem that we wish to solve.
2. Due to their age, Series Land Rovers will most likely have had several owners before we acquired the vehicle ourself. We should not therefore assume that previous repairs have all been carried out correctly or with good quality parts.
3. There may be more than one problem occurring simultaneously and we may be experiencing the combined effects of each of them.
4. A problem that re-occurs after a repair has been carried out, may not be due to the repair being ineffective, but that the original diagnosis was faulty and the problem infact lies elsewhere.
Each of the above four points will now be considered in more detail.
The term "symptoms" is being used in the widest sense. It may be a sound, a smell, or a driving effect such as jumping out of gear or lack of engine power. The fewer the symptoms, the easier it should be to reach a diagnosis. If there are several symptoms, then vehicle history becomes an important factor. We need to recall carefully how long each symptom has been evident. We also need to be open to the idea that a long standing symptom may or may not be related to a newly noticed one. For example, a long standing oil leak from the flywheel housing drain plug hole may well be related to a more recently experienced slipping clutch: suggesting that simple clutch adjustment may not be the cure, but that the clutch actually needs replacing. Alternatively, an ignition warning light that fails to fully extinguish, may not mean that there is a problem with the dynamo/alternator if a recent modification to the electrics has been incorrectly carried out.
Sometimes it can be helpful to think what symptoms may be missing if a particular diagnosis is being considered. For example, if the starter motor fails to turn over the engine, the reason could be a discharged battery. If that is the case, then the headlights should not stay bright for very long when switched on. If there is no problem with the lights then the starter motor or its circuitry can be suspected.
2. Vehicle history
The average age of a Series Land Rover means there will be a lot of history. Fault diagnosis is generally based upon the assumption that the mechanical aspects of the vehicle are as they should be and that no parts are missing and none have been fabricated or substituted by parts from other non Land Rover vehicles. For example, a sharp thud sound occasionally heard from the front of the vehicle when cornering, could be due to loose U-bolt fixings. But it could also be due to somebody forgetting to re-fit the slotted nut securing the halfshaft, so the halfshaft 'floats' more than it should do. Maintenance and repair books do not list options like this.
Problems related to vehicle history are particularly relevant if you have not owned your Series Land Rover for very long. So when buying a vehicle it is useful to question the previous owner and gain in your mind some idea of what their mechanical competence is, especially if they admit to having maintained the vehicle themselves.
3. Multiple causes
When one component in a vehicle becomes worn, or fails, then it will have effects on other parts that are mechanically associated with it. This is one reason why minor problems should not be ignored. To ignore them is to allow them to expand in scope and a correct diagnosis may rely upon you being able to recall the initial minor problem. For example, it can happen that the voltage regulator for the fuel and temperature gauges can fail causing these gauges to read low. If this is not remedied then a problem due to engine overheating is less likely to be avoided.
4. Recurring problems
Problems can sometimes come back, even though a remedy has been carried out. It may be that the remedy was not carried out correctly, but it could also be that another problem has lead to the same symptoms being observed. So the remedy was successful but another fault now has to be found and rectified. For example, Series Land Rovers are not renowned for their acceleration, but when it is particularly poor, it may be that blowing air through the jets in the carburettor improved the situation, but then the problem soon returned. In this case it could be that the additional fuel filter that owners often install had become partially blocked - even though it may have been renewed recently. So the initial fault was correctly dealt with but now a similar fault has occurred due to the common factor of contaminated fuel.
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