Oil pressure warning light, any ideas?

Good evening all
I just finished today 3 weeks project on my 2004 td5 disco. I replaced my exoust manifold gasket. I had 3 broken studs that I had to extract. 2 of them went out nicely and the last one I had to drill and make a new thread. I tried to extract them with welding as well so I disconnect the battery and took the ecu apart to be safe than sorry.
After I finish all the job I wanted to start the engine to bleed the cooling system ( I replaced the small cone hose under the manifold). The oil pressure warning light stayed on. For sure it wasn't the situation before. What can be the reason for that?
There is no oil missing....

One more thing.... I took the a/c compressor apart as well....

When you say "took apart" do you mean stripped it down or simply took it off the engine?

Took it off the engine.... sorry for my english

Menash said:

Took it off the engine.... sorry for my english

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Don't apologise, my Hebrew is rubbish!
How long did you dare run the engine before stopping it out of fear of breaking it?

10 sec max. I an not a brave man when it comes to my disco

Menash said:

10 sec max. I an not a brave man when it comes to my disco

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Right.
Did you remove the turbo i.e. disconnect the oil feed to it, or just move it aside?
I don't think the A/C compressor has an oil feed but I may be wrong on that.
Anyway, if you did disconnect the oil feed to the turbo, undo it again and top it up with oil, we call this "priming".

Very possible you could of either unknowingly unplugged or damaged the Oil pressure switch which sits just below the exhaust manifold, near the bulkhead.

Only way you'd lose oil pressure from the feed is if it was pishing out, I think you'd notice.

Henry_b said:

Very possible you could of either unknowingly unplugged or damaged the Oil pressure switch which sits just below the exhaust manifold, near the bulkhead.

Only way you'd lose oil pressure from the feed is if it was pishing out, I think you'd notice.

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I had read that an unplugged oil pressure switch defaulted to "light off" but maybe I'm wrong.

Stanleysteamer said:

I had read that an unplugged oil pressure switch defaulted to "light off" but maybe I'm wrong.

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If the switch is faulty or wiring unplugged or damaged it defaults to light on..

Henry_b said:

If the switch is faulty or wiring unplugged or damaged it defaults to light on..

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That makes totally sense, commonsensically.
Which just goes to show how much bullsh!t is talked on LR forums!!

Henry_b said:

Very possible you could of either unknowingly unplugged or damaged the Oil pressure switch which sits just below the exhaust manifold, near the bulkhead.

Only way you'd lose oil pressure from the feed is if it was pishing out, I think you'd notice.

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I was just thinking that maybe he wasn't giving it quite enough time to pressurise the system and prime the turbo.

Stanleysteamer said:

I was just thinking that maybe he wasn't giving it quite enough time to pressurise the system and prime the turbo.

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Oil pressure would be near instantaneous, the turbo is fed oil constantly "obvs" and drains away every time the motor is turned off so that's unlikely to be the case.

it would lose prime is if the oil pump sucked air from a lack of oil in the sump for example, but I doubt that to be the case from just turbo removal unless the feed was left disconnected which I think he would notice

Henry_b said:

Oil pressure would be near instantaneous, the turbo is fed oil constantly "obvs" and drains away every time the motor is turned off so that's unlikely to be the case.

it would lose prime is if the oil pump sucked air from a lack of oil in the sump for example, but I doubt that to be the case from just turbo removal unless the feed was left disconnected which I think he would notice

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The turbo would also be "noisy" to say the least.
We'll just have to wait and see. He has oil in the sump,as he said the level hasn't dropped.

Henry_b said:

If the switch is faulty or wiring unplugged or damaged it defaults to light on..

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That would be a far more logical way of doing it, but it isn't. The pressure switch closes at low pressure and opens when the pressure is above about 0.5psi, switching off the light. Unplugging the switch, cutting the wiring, would also switch off the light.

The operation is described in the WSM in the instruments section and can be cross checked in the wiring diagrams.

If the OP unplugs the switch and the light goes off, the switch is putting the light on, either because it is faulty, or because there really is no oil pressure. If the light stays on, there is a "short to earth" wiring fault/damage.

PopPops said:

That would be a far more logical way of doing it, but it isn't. The pressure switch closes at low pressure and opens when the pressure is above about 0.5psi, switching off the light. Unplugging the switch, cutting the wiring, would also switch off the light.

The operation is described in the WSM in the instruments section and can be cross checked in the wiring diagrams.

If the OP unplugs the switch and the light goes off, the switch is putting the light on, either because it is faulty, or because there really is no oil pressure. If the light stays on, there is a "short to earth" wiring fault/damage.

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Oops!

Well I thought this too having done a bit of research but I don't have our 'Enry's experience.
I think I'd better just hold the popcorn!!

Is any of us going to dare raise the issue of the oil pump chain sprocket bolt?

Stanleysteamer said:

Right.
Did you remove the turbo i.e. disconnect the oil feed to it, or just move it aside?
I don't think the A/C compressor has an oil feed but I may be wrong on that.
Anyway, if you did disconnect the oil feed to the turbo, undo it again and top it up with oil, we call this "priming".

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Yes, I did disconnect the oil feed hose

Henry_b said:

Oil pressure would be near instantaneous, the turbo is fed oil constantly "obvs" and drains away every time the motor is turned off so that's unlikely to be the case.

it would lose prime is if the oil pump sucked air from a lack of oil in the sump for example, but I doubt that to be the case from just turbo removal unless the feed was left disconnected which I think he would notice

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I am afraid I left the oil feed hose uncovered and unprotected. unfortunately, I thought it will be OK to screw the bolt back to the turbo without the hose as the only protection on the oil system.
It that's the case... primming the turbo (topping it up) would be sufficiant?

Menash said:

I am afraid I left the oil feed hose uncovered and unprotected. unfortunately, I thought it will be OK to screw the bolt back to the turbo without the hose as the only protection on the oil system.
It that's the case... primming the turbo (topping it up) would be sufficiant?

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Sorry again as still not quite sure what you have done, but you cannot have the turbo spinning with no oil feed, it'll ruin the turbo bearings. So you need to put it back together as it was before you undid it, and it is wise to "prime" the oil feed to the turbo. Although it isn't in the manual. You also really should replace the two copper washers though you will probably get away with it if you fit the old ones.
If you took the oil feed tube off the turbo and just left it there, provided no dirt got into it it'll be OK.