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Ok, I have a theory. I have noticed on a few Northstars' now that there is more wear on the furthest lifters from the oil pump, I notice for instance that there is more lifter wear on the lifters on #6 and #8 cylinders. As we know, at idle the oil pressure can drop to below 10 psi, before the low oil pressure light comes on (around 6 psi). This pressure may be adequate for a Northstar when all clearances are within tolerance but as the engine ages, the clearances in the rod bearings, main bearings, cam bearings, lifter bore and oil pump can widen effectively lowering the oil pressure below the 10 psi. A search of the board here for the term "flickering oil light" will turn up a bunch of members complaining of "oil light flicker" at idle, including me in my 96 Deville. Heavier oils like Rotella 15W40 in the warmer months can help manage it. A thicker oil will increase the oil pressure as it will not flow through the widened clearances throughout the engine so easily, thereby increasing the oil pressure slightly to stop the light. But I can not help but feel that my oil pressure is hovering just above the oil light ON, threshold at idle when I solve the light that way.

But, what is actually happening when the oil pressure is low to the point of the light coming on? I believe that points furthest from the oil pump will starve for oil first. I think the reason why I see wear in #6 and #8 is because its the last place the oil gets to on start ups especially when clearances are at or beyond their limit throughout the engine.

I would like to increase the oil pressure throughout the engine. Is there a way to increase the oil pressure by increasing the tension on the pressure relief valve in the oil pump? I would like to increase the oil pressure throughout the engine by 5 to 10 psi. Shim? Stronger spring?

Any ideas?

Also, please post your experience with regard to observations of lifter wear. Do a comparison of the lifters in cylinders #1 and #3 verses the lifters in #5 and #7 and also do the same in #2 and #4 verses #6 and #8. See if you see increased wear between those two samples as I have been seeing and post your findings here.

Thanks for your ideas.

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Hmmm..... I don´t think that would do it. The valve only take away the (too) high pressure on high revs and You don´t want only a higher top value. When low pressure on low revs the valve is closed.

The pressure fall on low revs comes from worn bearings. Only ways to correct this is: Higher flow volume (high capacity oil pump), thicker oil (5/40-5/50) or reduced wear (new bearings).

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Thanks Goran, hmmm not easy to increase...

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Body, your loosing pressure thru your main bearings and or a stripped main bearing bolt. Can you ship the motor to me for repair?

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Barczy, actually I am not losing pressure at this time. Above I was talking about a condition whereas the lifters in 5 and 7 and 6 and 8 appear to show more wear than 1 and 3 and 2 and 4. I believe its due to the system pressure getting lower at idle as the engine ages. If it were possible to raise the pressure 5 psi at idle I would be thrilled.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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If there is a way to increase idle just slightly then with the 100rpm increase the pressure should raise slightly. Its a jury rigging way that is not a fix just a temp cure. If the throttle pulley has an set screw for a stop then the screw can be set out just a little. Or any other way to increase idle speed.

On some of the older Mercedes diesels there was a low oil pressure at idle problem. When told a high dollar engine replacement, lots of people sold the cars to us( technicians ). We would adjust the throttle stop and give 100 more rpm and drive car for many years and miles.

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I dont know if that would work as the IAC in theory would correct the idle thus making the set screw adjustment not work

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I like your thinking jwoods, when we have the flickering oil light all it takes is a slight increase in rpm to turn it off. I would like to install an oil pressure gage on the northstar. I need to find a way to do that, I imagine that there is a tap on the oil filter adapter.

Rockford, you are correct, the engine management system would attempt to compensate for the increased rpm.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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lol rockford.

What do you consider high miles? I had over 200k and had no problems with my 96, never once did the oil light come on. Maybe it was broke lol.

I preach to only use AC Delco filters. I figure oil filter is cheaper than engine problem later

GM FAN FOREVER

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lol rockford.

What do you consider high miles? I had over 200k and had no problems with my 96, never once did the oil light come on. Maybe it was broke lol.

I preach to only use AC Delco filters. I figure oil filter is cheaper than engine problem later

Very true on the oil filters. A cheap oil filter is made cheaper by saving on build cost. The oil pressure relief valves normally are inferior. The filter element is made cheaper and the housing is cheaper. An oil filter cutter is a cheap tool to have, its amazing when I cut a filter and compare from a cheap filter to a name brand OEM filter.
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My 96 had the flickering oil light at about 125,000 miles. I did have a deep main bearing knock, so maybe there was a mechanical problem. I always use ac delco oil filters especially since I cut one apart last month and saw how good it was made. A slight boost in idle rpm would help

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

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It is not just how cheap they are made,

Sometimes they restrict the flow because they have to much filter material. It may not seem like much but at idle it makes a difference

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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BBF, i had the "STOP ENGINE" oil flicker/steady for a few years. I changed the sending unit, and that did not fix it, then i added motor honey. I have not seen it even flicker in about 2 years. I am hopeing that the additative increased the oil pressure like it says it does. In my case, when i was stopped at a light with the oil light on, no matter how high i reved it, the light did not go out or stop flickering. It would not be until i shut it off, and restarted that would make it stop. I guess my case got extreme? But again, this scarry ordeal is all behind me. I think since i started drving it again also helped loosten things up too. My only input to this would be the idea of some kind of external electric oil pump to distribute some oil to that section of the engine, but would have no idea if that is even possible or would help.

I am planning a trip in my '96 from North New Jersey to Florida in 2 weeks to visit my parents. I will take it slow and steady. Been runnng like new lately.

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Winterset, that should be a great trip. Yes I experienced that the 15w40 rotella helped and it did seem worse after it sat for awhile. Your flicker did sound bad that an rpm bump didnt remedy it. Are you driving straight through or stopping?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Wow...long run for you personally

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Good thing with the highway driving on your trip it'll be mostly above 1800rpm. Only time for low rpm is food/fuel/bathroom breaks. Hopefully you don't catch any bad traffic jams. Have a good and safe trip.

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