what causes lack of oil pressure need help

[ross501]

have a 300tdi with a lack og oil pressure changed pressure switch and while switch was out cranked engine and no oil came out changed pump and pressure switch is okay any suggestions

[Range Rover Blues]

If there's no iol coming out of the oil switch ole then you have a fundamental problem.

Your pickup pips might be blocked

The pump might be stuffed

there might be a serious internal leak, like the pressure relief valve being stuck open.

If the oil filter was blocked I'd expect to find a bypass valve, but it might be worth having a look at the filter too.  If nothing else you could see if there was oil getting that far.

Oh, and doesn't the oil go round the radiator too? you need to check that.

I'd suggest to save excessive wear on the engine that you remove the glowplugs whilst you are checking and disconnet the deisel valve.

[ross501]

i have checked the pick up changed the filter and checked the pressure switch also changed oil and filter
 

[Guardian.]

CRANK KNACKERED, mine ran sweet as a nut but lost pressure, changed everything before found out crank was totaly shot, but you would never believe it to drive or listen to, but no doubt it wouldnt have done many more miles before it gave up the ghost.

[ross501]

mine is still running but there is no oil getting round anywhere

[Guardian.]

mine still ran and drove it for about 3 weeks with the light flashing on and off, but when i got around to asking my man to have a look it was on more than off, still drove fine and no knocks or anything, but he took sump off and it was kaput.

[ross501]

not had the light flashing at all just came on and has stayed on since

[Guardian.]

i dont know how mechanically minded you are, but if you aint sure i would get it in a garage before you do out else, it maybe something quite minor that you make major just messing around with it, as no oil pressure is terminal if not addressed straight away.

[Range Rover Blues]

Do you know what grade of oil is in there?

The fact that it came on and stayed on tends to make me think something has broken, rather than worn out.

If you take it to a garage, get it towed in, don't drive it.

[ross501]

10 40  oil is in it

[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