: Oil Pressure...

06-10-11, 03:52 PM
I have a 97 Deville with about 130,000 miles on it (cue the dirge :p). I have been getting flickerings of the oil pressure light. I haven't replaced the sensor, but I'm reasonably sure it's not the sensor because it happens under very consistent conditions. Of course, when the engine is well warmed up, particularly in hot weather, the light will flicker occasionally when I come to a stop/idle. There is sort of a waxing and waning rhythmic rapping (by this, I mean that it's sometimes more noticeable than others, not that it gets faster and slower or anything), which comes from the side of the engine with the pulleys. I've thought that it is perhaps the power steering pulley, which I see is ever so slightly out of true. Not sure on that though, but it's definitely coming from that side/area of the engine.

Regardless, I know oil pressure is bad, the service manual is in the mail to me and I'm bracing for rebuilding this brick, but I was curious if anyone could tell me just what causes low oil pressure. I'm sure it's many things, but typically? I'm wondering if main bearings, etc... could cause it, or just what (if any) "extras" I might find I need to replace if I open this thing up. Just for the record, I've never rebuilt an engine before, and I'm sure the N* is just an absolute beauty to start on, but I've had an engine down to it's valves, timing chain and manifolds off and such before.

06-10-11, 04:11 PM
You would not be the first to have an "iffy" oil pressure sending switch; it's pretty common in these troubleshooting threads.

BEFORE you tear into the engine for a perceived problem, either you or a shop substitute a mechanical oil pressure gauge for the sending unit and do a running pressure test - it's a PITA, yes, but it's the only sure way to eliminate the sending switch. AC Delco only.

FWIW, GM (over the years) seems to like about 20 psi at hot idle, 40+ at hot 2,000 rpm. The sending switches are calibrated to close at about - about - 5 psi.

What causes low oil pressure ?? Zillions of things - oil aeration from overfilling, bad sending units, slipping oil pump drive, broken oil pressure relief spring, restricted oil filter, excessively worn hydraulic lifters, cam bearings, rod bearings, crankshaft main bearings, internal leaks or oil passage cracks, cracked oil pump pickup tube, restricted oil pump pickup screen. (At 130,000 your main and rod bearings are probably still within specs.)

06-11-11, 01:33 PM
i have not replaced the sensor and i know my oil pressure is low. wrong. only thing you know is your light flickers at hot idle. you should use 5w-30 or 10w-30 depending on your mood. try replacing a few qts with xx-40 oil. that will give you a little more hot viscosity help. change your pressure sensor if you feel like it.

07-12-11, 09:30 AM
sorry for my bad english, I am from europe ,Lithuania.

I have cadillac eldorado 96 with about 118k miles. my oil plesure is always ok but then i ride on very high rpm after that the oil plesure light starts flashing, but not for long. This is why?

07-12-11, 10:41 AM
Very possible and more than likely. The lower end including the oil pump are very reliable. It would be relatively cheap and easy to replace the oil pressure switch, but be sure to use an A/C Delco switch. You don't know how aftermarket switches are calibrated.

07-12-11, 02:51 PM

Yes, as Ranger posted it is very possible that after a high speed drive the oil is very warm and when the engine slows to a 650 rpm idle the sending switch could cause a light to flicker on and off.

I would guess that you get no oil light at first (cold) startup and maybe not even in everyday city or slow driving conditions.

Do you use a Euro 5W-40 oil ???..........that oil is different from ours and has a greater amount of anti-wear additives in it......... what brand names of oil filter are available to you ???

07-12-11, 11:00 PM
when i was changing oil I extraxt the sensor that is near the oil filter (i think that is oil pressure sensor) and saw that is spents oil out. but not on ebay or other internet shops i cant find it to buy. then i riding normal every day the presure light never flashes.
I using Elf oli 5-30 sintetic. i dont remember which brand of filter I bought, but all parts I buy from ebay and i think all brand is available. whitch is the best? whitch euro oil i shud use?

07-12-11, 11:16 PM
There is an oil pressure switch (sensor) on the filter adapter and an oil level sensor near it. You should not get too much oil out of the switch (sensor).

07-12-11, 11:27 PM
i think i need to change it because the oil it forces its way through. than you all you information becausi here in Lithuanina none can tell me nothink about cadillac and how to fix it :D

07-13-11, 10:38 PM
Oil Pressure Switch becomes a leak point frequently especially when it's old. You can put some teflon tape if it's just leaking, but replace it if you suspect it giving you false info. Also it's kinda in a tight space and a new unit will definitely provide you years of service.