Vehicle & Technical > Discovery

what causes lack of oil pressure need help

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Range Rover Blues:
Well personally I prefer 15w/40 escpecially when the engine gets older, though I doubt your oil has had a sudden viscosity failure :?

ross501:
its the same oil i always use but no one seems to know what is wrong with it

Range Rover Blues:
Forgive me if this is a bit Janet and John, but the oil pump picks up oil from the sump, forces it through the rad oil cooler and then the filter (IIRC).  Shortly after that it enters a gallery, a long drilling the length of the engine.  The pressure switch is connected to the galery, so are all the main bearings on the crank, arguably the most important single partof the engine and the one most in need of lubrication under pressure.

There is also a drilling into the gallery allowing a small amount of oil to run upwards into the head and from there into the rocker shaft before splashing over the valve stems and cam followers and running back to the sump.

The cam bearings may also be lubricated from the main galery.

So, assuming your oil pressure switch is not faulty you have one of two issues.
1) the oil pump cannot provide enough oil to build up any pressure, either by failure of the pump, the pressure releif valve or by blockage of a pipe, drilling or filter.

2) the oil is not being contained within the galery long enough for pressure to build up, ie it's running away too fast.  Either by leakeage in one of the drillings or by excessive consumption in the bearings of either the crank or the camshaft.

If the oil was escaping the engine completely I have to assume you'd have noticed by now, though it's worth checking.  The main oil galery is sealed often by either a ball bearing stamped into the end of the drilling or a grub screw threaded in.  Either way if one of those has come loose then it's potentially engine out time.  I've never heard of one failing though.

So check that there's oil in the filter and it's being pumped that far, you can check oil delivery to the head if you remove the rocker shaft you should see the top of the delilvery drilling under the front roacker pedestal, or you'll see oil all over the rockers-lots of it.

Did you say you weren't getting oil out of the pressure switch hole though :-. or have you not checked that far yet.

Depending how mechanical you are and how tight money is there might come a point when you decide to let someone else have a look, though paying themto do something you can check yourself is frustrating.

ross501:
i have checked everything and cant find anything wrong have admitted defeat and its in the garage now just got to wait for the bill

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