the engine will not operate; but simply to have oil present, is not by itself sufficient to maintain a healthy engine. The oil needs to be monitored for both quality and effectiveness in doing its job.
Good quality engine oil is a complex chemical system and should not be classed in the same league as the stuff you put on the garden gate hinges occasionally.
Failure to change the oil as required will simply bring on the need for an engine overhaul earlier.
Diagnostic signs in the oil
As with any vehicle, Series Land Rovers need good quality oil to be able to lubricate the moving parts of the engine effectively. Once the markings on the dipstick are invisible through the oil, then you know that it contains combustion particles and perhaps some debris from worn metal surfaces. The longer the oil stays in this condition, the more abrasive effect it will have upon the soft bearing surfaces of the crankshaft and conrods. If the oil develops a brownish colour then the most likely cause is water in the oil - possibly from a damaged cylinderhead gasket.
Low oil pressure
Without an oil gauge fitted (they are not normal on a Series Land Rover), your only warning of low oil pressure is in the extreme case of it dropping to around 10psi, when the green oil warning light will come on. Always check on engine start-up that this light comes on briefly - if it doesn't then check the bulb. If you have an oil gauge fitted, then the pressure at normal working temperature should not be less than 40psi when the vehicle is at cruising speed. Earlier Series Land Rover engines have higher minimum working pressures than later models (about 10psi range difference from the 1595cc to the 2625cc engines).
The most common cause of low oil pressure is worn
conrod bearings and/or worn crankshaft bearings. But the oil pump located in the sump of all Series Land Rovers has a gauze filter that can become blocked and some pumps have a pressure relief valve that can become jammed open. On some Series 1 engines this valve is adjustable.
Using the wrong grade oil or the engine overheating can both reduce oil pressure significantly.
All models of Series Land Rover are legendary at marking their territory with oil. But this can be discouraged and even illiminated with some effort. The secret, of course, is to renew seals and gaskets as appropriate - no easy task in some cases, but leaks from the large swivel hub seal can be minimisd by fitting leather gaiters; the gaiters prevent small bits of road grit getting under the oil seal lip, damaging the chrome surface and causing the leak. It is becoming common to use specialised grease inthe swivel ubs but this is not as effective as EP90, especially in winter.
If your Series Land Rover is marking its territory then a useful aid to pinpointing the exact point of departure from the vehicle is to place a lockable steel measuring tape on the oil spot and extending the tape upwards until contact is made with the source of the drips. You may need to look around this area though to establish the actual source of the leak itself.
If oil consumption is unusually high and there is little or no territorial marking taking place, then the exhaust emissions need to be checked, at least visually. A bluish coloration in the exhaust indicates oil in the combustion chamber, and this could have arrived from below, via worn/broken piston rings or enlarged cylinder bores. or from above, via worn/perished valve stem oil seals. If the coloration is mainly seen on engine start-up or after changing gear, then probably the cause is worn/persished valve stem oil seals or worn valve stem guides. If the coloration is seen whilst driving uphill or when accelerating then worn piston rings/cylinder bores are likley to be the cause and an engine overhaul is required. With care, valve stem seals can be removed without removing the cylinder head, but renewing valve guides requires the cylinderhead removing.
In petrol engines a perforated diaphragm in the emission control sytem can cause oil to enter the combustion chamber. In diesel engines a worn engine may tend to run-on after turning off the ignition - due to the oil being burnt as fuel.
Using a thicker grade of oil can temporarily reduce losses.
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