Oil light on, oil pressure at zero

[Chimp871]

Driving today and saw oil light come on but oil pressure towards the 30 psi mark. Over the next half mile the oil pressure slowly dropped to zero.

I pulled over immediately as i was on a country road and finally got towed home.

Theres oil in the engine, at full mark.

Any ideas where to look first?

Cheers

[phillpot]

buy/borrow/steal a mechanical oil pressure gauge.

[bobfather]

I thought the oil pressure gauge and the oil light were via separate sensors. If so then I'd say it's pretty conclusive that there's no oil pressure. Sorry that's not terribly helpful but a mechanical gauge may be wishful thinking

[bobfather]

Is it a pre-serp engine? If so perhaps the oil pump may need to be primed

[sheel]

Ouch sounds bit naughty loosing signal on both looks bad,they are different sensors/circuits loosing the gauge is not unusual but the oil light at the same time........
As a start you could whip the plugs out and fit a mechanical gauge and spin it up for a short while see if you have any pressure
You don't say which engine you have and I'm not familiar with the preserp pump arrangement but the serp pump is pretty robust could possibly the oil pressure relief fallen apart on the side of the housing but that's clutching at straws,full of oil,could the pick up pipe have dropped off?
Other will confirm but on the preserp does the pump run off a drive off the bottom of the dizzy? Possibly failed?

Sorry can't help more but sounds if you saved the engine by stopping in time. Best of luck
Rich

[Colin RedGriff]

Could be a blockage in the oil pick up from the sump. Several people in the past have had problems where silicon has been used to seal the sump and the excess has dropped in the sump then go caught in the pickup filter

[Chimp871]

sheel said:

Ouch sounds bit naughty loosing signal on both looks bad,they are different sensors/circuits loosing the gauge is not unusual but the oil light at the same time........
As a start you could whip the plugs out and fit a mechanical gauge and spin it up for a short while see if you have any pressure
You don't say which engine you have and I'm not familiar with the preserp pump arrangement but the serp pump is pretty robust could possibly the oil pressure relief fallen apart on the side of the housing but that's clutching at straws,full of oil,could the pick up pipe have dropped off?
Other will confirm but on the preserp does the pump run off a drive off the bottom of the dizzy? Possibly failed?

Sorry can't help more but sounds if you saved the engine by stopping in time. Best of luck
Rich

Opps... Serp engine, 98 450

[bobfather]

Colin RedGriff said:

Could be a blockage in the oil pick up from the sump. Several people in the past have had problems where silicon has been used to seal the sump and the excess has dropped in the sump then go caught in the pickgup filter

I have read on these pages of someone developing a leak on the pick up pipe above the oil pick up level. Like a syphon break but not. Air pick up will stall the flow by de-priming the pump

[jojackson4]

Pull the sump

[Chimp871]

jojackson4 said:

Pull the sump

I think this is the best. On a serp engine how do you run the pump with the engine off, just to check flow?

[Pupp]

Chimp871 said:

I think this is the best. On a serp engine how do you run the pump with the engine off, just to check flow?

You don't; the engine would need to be turning (it's direct driven on the crank nose) - as the others advise, drop the sump and chances are the strainer on the pick-up is clogged or the pick-up has fractured/come adrift. The serp pumps are pretty bullet proof.

What mileage has the engine done?

[Chimp871]

Pupp said:

What mileage has the engine done?

59k.

Hope it's a blockage, strange that it started off with pressure then slowly dropped down to zero. Scared the living st out of me.

The oil light was on (faintly) when I started but pressure gauge ok. Set off and 1/2 mile later oil light dimmed but pressure gauge started going down. I know both of these means its serious.

[pwd95]

Could also be the oil pressure valve stuck open. It's located just above the oil filter. Size of a 10p & held in by a circlip.
Give it a couple of healthy taps, pull the plugs & the fuel pump relay & crank it over for about a minute. The pressure will come up if all is well. Try this before getting messy.

[jesfirth]

pwd95 said:

Could also be the oil pressure valve stuck open. It's located just above the oil filter. Size of a 10p & held in by a circlip.
Give it a couple of healthy taps, pull the plugs & the fuel pump relay & crank it over for about a minute. The pressure will come up if all is well. Try this before getting messy.

Yup. Wot he said. Then change the valve.

[Chimp871]

Would a dodgy prv still allow pressure at low revs as mine did?

[pwd95]

Chimp871 said:

Would a dodgy prv still allow pressure at low revs as mine did?

Possibly not.....

Here it is on the end of the Red arrow...

[Chimp871]

Removed oil pressure sensor today. Spade was connected but sensor spade was loose in its housing. When i removed sensor i accidentally pushed terminal back in housing, it was that loose.

Sump is coming off tomorrow then I'll have a go at the prv.

Still concerned that the oil light came on and then lost pressure a few minutes later. A bit confused on this.

[Chimp871]

Dropped sump and inspect oil feed pipe. It was secure but had some sealant stuff before gauze filter but not enough?to restrict flow IMO. Cleaned it up and sump, mew seal and put back on.

Dropped oil filter and seemed ok.

Problem i had was with oil pressure release valve. Just could not remove the valve (bit that stick into block) without having to make a tool, finally came out after a lot leverage.

I'm no expert on these valves but would this being stuck in the block be likely source of oil light on and oil pressure drop to zero?

Edited by Chimp871 on Thursday 14th January 16:34

[Chimp871]

Edited by Chimp871 on Thursday 14th January 16:32

[Chimp871]