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Series Land Rover - Fault Diagnosis Exercise(Cooling System)

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Series Land Rovers are not known for suffering from overheating problems, especially the Series I, II and early IIA models. This is generally because the original design of the Series Land Rover incorporated the ability for the vehicle to act as a standing power source. The extra-large radiator was fitted as standard to compensate for the lack of natural airflow in a stationary situation. A variety of machinery could be operated via a power take-off device mounted either to the rear of the vehicle, in the centre or at the front and directly from the crankshaft. A previous UK homepage focussed upon the Cooling system basics


Twenty years after the introduction of the first Series Land Rovers the owner-demand for power take-off facilites decreased. So 1968 saw the replacement of the 4-row radiator with a 3-row version, popularly matched to the 2.25litre engine. The heavy duty 4-row radiator was still available as an option if required.

So let us now describe the scene for our hypothetical Series Land Rover with an overheating problem. The vehicle is a 1961 LWB Series IIA station wagon with the standard 2.25litre petrol engine and having the original 4-row radiator.

The problem is that on short runs around town, or longer journeys not involving much hill climbing, the vehicle performs well and the temperature gauge does not indicate any problem. If, however, the air temperature reaches about 30C or the journey involves repeated hill climbs or long sessions of motorway cruising at 50mph, fully loaded, then the temperature gauge rises above normal and care has to be taken to prevent serious overheating. On hilly sections it is possible to cool the engine significantly by easing off the accelerator on down slopes as much as possible. Switching on the heater also helps a bit in re-distributing the heat away from the engine. But on long motorway runs it becomes necessary to stop at a rest station and allow the engine to cool down.

It should be noted at this point that at least it is not the standard 2.6litre petrol engine that is fitted; the aluminium cylinder head on that engine is subject to damage if overheated.

Well the first suspicion is that there may be a problem with the radiator. A simple visual check reveals that there is no blockage of the radiator cooling veins by debris. Neither is there any loss of water through leakage. So water is there in sufficient quantity and air is able to pass through the radiator to carry out heat.

What if the water was not able to circulate properly internally? Allowing the engine to cool down significantly and removing the radiator cap, then revving the engine whilst warm, produces a noticeable turbulance in the water surface in the neck of the radiator. This indicates water movement is taking place, so there is no blockage and the water pump is working. The oil level is also checked as oil provides an important means of transferring heat around the engine. The level is OK and it is reasonably clean, so should be functioning as it should. The exhaust compression is checked simply by hand to test if there is a blockage that could restrict removal of heat via the exahaust system - it is found to be OK. Finally the wheel rims are felt to see if they are unduly hot due to binding brakes and thereby causing the engine to overwork. But they are not hot to touch.

So now the roadside diagnosis is complete and further examination needs to be done later.

To be sure that the coolant flow is not being just partially restricted, the radiator is removed and flushed out. Also, the top and bottom radiator hoses are examined for internal collapse of the rubber lining. Finally, the thermostat is removed and checked in a pot of gradually heated water to see if it is opening as fully as it should. The fuel mixture from the carburettor is checked and the valve tappets are checked, as these two can cause overheating if not correctly set. Finally, the voltage stabiliser that reduces the electrical supply to the temperature and fuel meter gauges to 10volt is checked. If it was 12volt it would cause a high reading on both meters.

The result is that the problem persists even after all these checks have been made.

Well the only check we have not made is that the coolant is able to pass around the engine block effectively. It's a 1961 engine and some rust is visible in the coolant so perhaps there is serious narrowing of the cooling channels by sediment. This can be aggrivated if a radiator sealant has been used in the past that is of the thick gooey type - as is occasionally still available.

So the radiator hoses are removed and a garden hose is secured to the top water outlet on the engine block and the engine cooling channels back-flushed at as high a pressure as possible. MAGIC - loads of rusty coloured sediment flows out and the problem has been solved.

A 2-part article on identifying and repairing serious overheating problems was covered in previous homepages.

(To see previous homepages visit the Homepage Archives link)


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