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Discussion Starter #1
Hello All,
I have a 2005 Outback with the single cam EJ25 engine. My problem is the Red Oil light comes on with really no rime or reason. The engine is a complete rebuild (bearings, oil pump, pistons ect.) When the car is cold (first start of the day) the idle is a bit faster until a few seconds and it comes down. No light issue here, but sporadically comes on at start up as the day goes on. As soon I rev the engine it goes off and doesn't come back on while driving. Then it could be a couple days and it might come on at start up again. I change the oil regularly with manual suggested Synthetic. then went to a higher viscosity, still occasionally comes on (only at start up). Then I replaced the oil sending unit with a new Subaru OEM unit and still comes on. Last ditch was to add some Lucas oil additive , and guess what ??? Still have the problem.
Any suggestions ?????
 

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Outback 2011 3.6R Premium
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The red oil can light means your oil pressure is low.This is a very serious issue and needs to be resolved to prevent engine damage.

You mention you have had the engine rebuilt AND subsequently replaced the oil pressure sending unit.

Oil pressure is generated by two components in an engine. At idle the main oil pressure comes from the oil pump with additional oil pressure being provided by the big end bearings/crankshaft.

As your oil pressure is low at idle AND you have replaced the oil pressure sender with a genuine Subaru part I am going to suggest that the new oil pump that was used when the engine was rebuilt is causing the problem. This may have been a non Subaru part which may not be operating as per design by Subaru.

To confirm your oil pressure is low you could remove the oil pressure sender and temporarily install an oil pressure gauge and check the actual pressure reading.

With your 2005 EJ25 engine I would be using 10/W40 or 15W/40 oil which are oils designed for that engine and offer better oil pressure at idle than the commonly used 5/W30 oils. The other thing that you could try is a change in oil brand as some oil brands have better oil pressure at idle than others.

Seagrass
 

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2005 Outback VDC limited 3.0r
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Do you mean just the 1st second on start up? Or like 5-6 seconds? If its 1 second or less, generally that's normal since the engine hasn't gotten enough speed to build the pressure to the sending unit. Disable the fuel injectors or pump by pulling the fuse, crank for sometime and see if the light goes out. Should take about 5-6 seconds of cranking.
 

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Discussion Starter #4
The red oil can light means your oil pressure is low.This is a very serious issue and needs to be resolved to prevent engine damage.

You mention you have had the engine rebuilt AND subsequently replaced the oil pressure sending unit.

Oil pressure is generated by two components in an engine. At idle the main oil pressure comes from the oil pump with additional oil pressure being provided by the big end bearings/crankshaft.

As your oil pressure is low at idle AND you have replaced the oil pressure sender with a genuine Subaru part I am going to suggest that the new oil pump that was used when the engine was rebuilt is causing the problem. This may have been a non Subaru part which may not be operating as per design by Subaru.

To confirm your oil pressure is low you could remove the oil pressure sender and temporarily install an oil pressure gauge and check the actual pressure reading.

With your 2005 EJ25 engine I would be using 10/W40 or 15W/40 oil which are oils designed for that engine and offer better oil pressure at idle than the commonly used 5/W30 oils. The other thing that you could try is a change in oil brand as some oil brands have better oil pressure at idle than others.

Seagrass
If it was a main bearing issue, the light would stay on at a idle. It wouldn't come on sporadically either. As I mentioned, it never comes on first thing in the morning. Thus giving a idea of a viscosity issue. But as I have tried different weights, Lucas additive and Seafoam. Still comes on sporadically and will go off immediately after hitting the throttle once.
 

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If it was a main bearing issue, the light would stay on at a idle. It wouldn't come on sporadically either. As I mentioned, it never comes on first thing in the morning. Thus giving a idea of a viscosity issue. But as I have tried different weights, Lucas additive and Seafoam. Still comes on sporadically and will go off immediately after hitting the throttle once.
So if it idles it just stays on? I would stop driving it and take it to the engine builder, something is not right. Oil light coming on for 1 second or less at startup in general generally isn't a problem. But, since it stays on until you rev it, there is a problem.
 

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2002 Subaru Legacy Outback.. Base or L. 4S3BH/EJ251
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Do you hear any clack-clack-clack noise at start? None?

Is there sludge in your engine?
 

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2002 Subaru Legacy Outback.. Base or L. 4S3BH/EJ251
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No Noise, No sludge.
What grade of oil you got in there?

About to ask other members of choice of oil filter would make a difference.

Basically.. you have an engine that seems to run okay, yet you get the low oil pressure indicator light, which is that red oil can light ? And no engine shaking?
 

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Discussion Starter #9
What grade of oil you got in there?

About to ask other members of choice of oil filter would make a difference.

Basically.. you have an engine that seems to run okay, yet you get the low oil pressure indicator light, which is that red oil can light ? And no engine shaking?
Mobil 1 5W-30, Then Mobil 1 10w40 Synthetic. The Light doesn't say on when when you hit the throttle once. It doesn't come on while driving or idling at a light. It doesn't come on everyday either.
 

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2020 Outback Premier 2.5i
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Disable the fuel injectors or pump by pulling the fuse,
On these older models, can't the injectors be shut off with a fully depressed throttle? IIRC that's how you prime inverted oil filter after a change.

I agree with the notion to go back to the installer for discussion. There might be an issue with a cracked or partially blocked pickup tube (tube bent down, pan bent/dimpled up, left over rag/oil wipes left in the pan is not unheard of), bypassing pump seal, etc. , any of which could cause repeated lack of pressure at startup.
 

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2002 Subaru Legacy Outback.. Base or L. 4S3BH/EJ251
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Mobil 1 5W-30, Then Mobil 1 10w40 Synthetic. The Light doesn't say on when when you hit the throttle once. It doesn't come on while driving or idling at a light. It doesn't come on everyday either.
And it comes on randomly?

It should be most likely to come on at an idle... Does it?

Any RPM will be generating oil pressure. Can you run down when it does/doesn't come on again, please?

And you said it's NOT making noise, low on oil noises, engine shakes, delay in throttle response... Things that low oil level can do?
 

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2006 Outback 2.5i manual
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I agree with much of the above. Personally, if it were me, I'd find a spot to tap in an oil pressure gauge. With that you'd be able to see if there is any consistency in losing pressure. From there you could get closer to diagnosing where the loss in pressure is coming from.

Good luck, and keep us updated on what you find! Hopefully it's something simple like a partially clogged/blocked oil pickup screen.
 

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2002 Subaru Legacy Outback.. Base or L. 4S3BH/EJ251
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It sounds like something in there is blocked (partially) to me too.. I would have thought maybe sensor if my engine was running okay and not showing any signs of running as if it actually had low pressure, but this is all happening after a rebuild too so.. I wonder.

I also want to say trying either Mobil 1 0W-30 Advanced Fuel Economy or even Mobil 1 0W-40, even Mobil 1 15W-50 (tests show it's more like a 10 on its W rating and people routinely report starting it in 0 degree weather just fine) but maybe we haven't gotten there yet.

I would agree that getting a mechanic gauge where you can actually get out, open hood, and read oil pressure would be very helpful. IIRC the red light is an idiot/emergency light that only comes on when oil pressure is like 5PSI or so.
 

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How long since the rebuild?
 

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oil pick up may be blocked if they have used gasket sealer to double seal the sump ... when the sump is tightened down some of the sealant may get squeezed and be left floating in the sump .... i have heard of this happening before .. reducing the oil pick up due to partially blocking the oil strainer in the pick up
 
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