Sudden loss of oil pressure- what is the most likely culprit?

[genphreak]

Ahem. Er. hmmm.

I changed my plugs on the M30 this weekend. Started the car up this morning (it fired straight away) but faltered slightly (stry) straight after ignition. Then it ran fine, but I noticed a very slight and unusual noise; sounding a bit like what I would expect cavitation to sound like, coming from the oil sump.

Others may not notice it, but I know the sound of my engine well and was actually listening for exhaust leaks (as I need to replace the exhaust springs and occasionally I have to tighten the engine pipe>manifold nuts as a result).

Now the engine had not been started for about 10 days- so the 'cavitation' I thought would go away. Sure enough it seemed to quieten down a lot after 20 seconds becoming almost negligable.

BUT, I was surprised to notice the oil warning for the first time ever. (I guess) it normally goes straight out after first ignition (which I've never noticed, even with the ignition on and motor not running). I know, I know, pay attention amateur wrencher!.

This time the light wouldn't go away. There were no other noises and I moved the car forward a little thinking oil pressure might be taking a while if the canister had emptied ove the 10 day period. After opening the oil cap to check for oil spraying over the valves on cylinders 5&6 I found none, so I shut it down immediately and used the other car.

It ran for perhaps 90 seconds in total. Oil pressure warning was clearly displayed on the dash all this time and did not go away. No rattles or other weird noises, except for the slight hesitance on starting.

For all I know it might be the infamous canister check ball but I don't think so- I've never seen an M30 not spill oil to the top end properly and I didn't want to risk damaging the motor if there was indeed a problem.

Maybe it's my imagination but weren't M30 oil pumps (pretty much) bulletproof? Has anyone seen one fail- or the drive chain break before?

Was thinking the next test would be to pour some oil into the head (for good luck) and then remove the oil pressure switch, crank a little and check to see if oil spits out...

If this fails, is it really a matter of pulling the pan and looking for bits of disaster?

Oh, and before anyone asks, the oil level is still at 3/4 (she spills perhaps a few drops a week as most M30s do) but has never needed a any topup between changes.

What do you all think? Was I being a Woose shutting it down? Did I not give it enough time to get pressure up?

Many thanks in advance for any suggestions, Nick

[Espen]

Shouldnt take much longer than a coupple of seconds before oil pressure is up, even after a long periode of no use. I would check the oil pressure with a "real" meter before doing anything else. If you indeed have a oil pressure problem, i would check the oilpump. The oil pump chain can go to h"#, it did that on my ford.

[BillionPa]

when the pump is sitting in the pan, its pickup is submerged in oil, so it should be going everywhere.

what oil were you using?

if its dino oil, i feel bad, as it really doesnt provide much protection under those circumstances, and the oil feed lines are probably all sludged up causing the oil starvation.

if you havent noticed im a synthetic fanboy...

[632 Regal]

we should do another pole.

if you havent noticed im a synthetic fanboy...

[Jeff N.]

.

we should do another pole.

[632 Regal]

yours wasn't much better...

[Bleeding_Knuckles]

did you put a guage on it yet to see if its really low pressure?

[mamilapon]

When was the last time you checked the oil spray bar bolts?

[Martin in Bellevue]

yours wasn't much better...

That neither of you had much to offer here. That makes us all sad.

Gen, I'd drop the filter cannister in the hopes of finding it relatively full of oil. If it is half full, then I'd pull the oil pressure sender at the top rear of the head & crank, not start, in the hopes of catching a stream of oil in a rag. If no pissed oil, I'd then consider pulling the pan to look at the oil pump, after inspecting under the valve cover.

Good luck.

[genphreak]

When was the last time you checked the oil spray bar bolts?

Thanks for all the replies guys.

I checked the banjo bolts (and torqued/loctited them in clean threads) when I did the head about 12,000 miles ago (and 2 oil changes). Need to look again of course. Oil is factory spec dino oil 20W/50 as Australia is a not cool country.

Next step will be to check for pressure and pull the cover and oil canister- I'll let you all know how this goes next weekend. I'd really like to have a remote setup, so who knows, that may well be on the cards now...

I am feeling dumb for not checking more thouroughly just recently: In the last week she was running I twice heard the head sounding like it was a bit short on oil (only under load), so I checked the level but didn't pull the timing cover or do a pressure test. I figured the idiot light should be telling me something. Hey, now I really know why it is called the IDIOT light!

So now with a clearer head (and your advice) I suspect the pump may have been starting to go... however it may also be a blockage somewhere. However if the pump is suspect, what does one do?

I think it'd be prudent to have on hand a pan gasket, oil, coolant front timing cover gasket set. To be frank I want to change the oil pump and its drive whether it ends up being faulty or not, the fear of running out of oil really gives me the willies...

Does one get a new oil pump or rebuild the old? The ETK lists the internals, ie parts 2,3 & 4 below.

I will also do 13,15 & 16 (pump chain, sprocket and tensioner arm) which of course, I should bloody well have done last time!! I have a new crank sprocket here, so hope that with these parts I'll have enerything on hand...

1OIL PUMP111411317100$364.93
2ROTOR INNER111411267380$35.71
3ROTOR,OUTER111411250504$21.32
4INTERMEDIATE PLATE111411714755$2.12
5OIL PUMP COVER111411289145$82.03
6HEX BOLT WITH WASHERM6X25-Z367119915046$0.39
7PISTON111421271320$3.35
8COMPRESSION SPRING111411744324$0.88
9SPRING POCKET111411267050$3.74
10LOCK RING16X117119934619$0.17
11HEX BOLT WITH WASHERM8X30-Z317119915085$0.50
12HEX BOLT WITH WASHERM8X45-Z327119912970$0.31
13SPROCKET111411707147$44.08
14HEX NUTM10X117119900079
15CHAIN111411707163$26.51
16CHAIN TENSIONER111411705055$16.07
17BEARING BOLT111111706500$4.52
18BUSH111311706503$0.33
19CIRCLIP6,017119932842$0.04

Thanks again friends! Nick