Cadillac Owners Forum banner

1 - 20 of 57 Posts

·
Registered
Joined
·
282 Posts
Discussion Starter #1
1998 Seville STS, 75K miles. Using Shell Rotella 10W30 non-synthetic. Oil pressure light comes on at idle after driving 20 miles in 90 degree heat. Replaced OP sending unit with new AC Delco unit and same problem. Put a mechanical gage in the unused oil cooler port and it reads 12-15 lbs at idle and OP light is flickering and sometimes constant but "LOW OIL PRESSURE" message has yet to pop up on the DIC even when light is constant for 10-15 seconds. At 2000 RPM pressure is reading 40-45 PSI at operating temp. At cold start up pressure reads above 60 PSI at idle.

Mechanical gage is always fluttering around 5 PSI at all RPM's, never a constant number.

I'm reading that the OP switch is supposed to be set for something like 6 lbs.

Any suggestions?
 

·
Registered
Joined
·
7,345 Posts
Re: Oil pressure light on at idle.

I've had similiar issues with my 97, changed switch out also. About a month ago I loosened and retorqued the balancer bolt(drives oil pump), I also switched to a 10w40. Seems to so far to be working. I suspect it was the oil myself(dino oil can't remember brand I used when having issues).
The balancer bolt is hard to judge if it was tight enough beforehand and since it popped up just before Christmas last year is why I think mine didn't like the oil I used.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #3
Re: Oil pressure light on at idle.

Thanks rodnok.
I was hoping to hear some actual oil pressure readings at idle from others. I just purchased this car in March with blown HG's and wanted to fix it then flip it but I can't sell it with this oil pressure issue going on. I ended up doing a total rebuild because the engine had gotten dusted a little due to the intake muffler being disconnected from the main intake plenum and the cylinders had some light vertical scratches so I de-glazed the cylinders and replaced the rings, new main and rod bearings, rod bolts, oil dist manifold, head studs and a few lifters. Ran a 20 minute break in at 2000 RPM, changed the oil then put 100 miles on it and changed the oil again then again after another 500 miles. Each time the oil comes out looking like new, no silvery tint like it's got bearing material in it. This problem has now shown up since its gotten into the upper 80's and low 90's here and the car is driven about 20 miles.

At the first oil change there was some debris in the filter which I expected but the next 2 filters looked really good. So now I'm wondering if maybe a pc of debris got stuck in the oil pump pressure bypass valve and not letting it close all the way at idle because I know it's open at cold start up and probably open some when at operating temp while driving down the highway when the oil pressure is reading 40-50 PSI. Maybe this also explains the fluttering on the mechanical gage at idle.

I'm also wondering if the Shell Rotella maybe runs a little thinner at operating temp. Maybe I'll try some Valvoline 10W30 and see if it's any better at idle. I know in my Diesel Motorhome I run the Shell Rotella 15W40 and at cold startup it pegs the pressure gage at 100 PSI at idle but once it reaches operating temp it will drop to 20-25 PSI at idle.

I'm still baffled at why I'm not getting the LOW OIL PRESSURE STOP ENGINE message on the DIC when the light comes on.
 

·
Super Moderator
Joined
·
86,145 Posts
Re: Oil pressure light on at idle.

I'm still baffled at why I'm not getting the LOW OIL PRESSURE STOP ENGINE message on the DIC when the light comes on.
Because the PCM thinks you lost oil pressure.

Just replace the switch, but be sure to use an A/C Delco switch. Stay out of AutoZone :tisk:

I'm also wondering if the Shell Rotella maybe runs a little thinner at operating temp.
All oils will run thinner at temp. I run it (Rotella 10W30) in my '69 Road Runner and it runs close to operating pressure at idle when cold, but drops to about 25 when at operating temperature.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #5
Re: Oil pressure light on at idle.

Just replace the switch, but be sure to use an A/C Delco switch. Stay out of AutoZone :tisk:
I did replace the sending unit with a AC Delco unit and it was not any better. Oil pressure light would flicker at hot idle and eventually would stay on constant but no "LOW OIL PRESSURE" message and mechanical gage was showing 12-15 lbs at oil filter adapter.

Today I was able to trick the the system using the old sending unit by just plugging it in and grounding it and then the "LOW OIL PRESSURE" message came on so I know that the warning system is working. So I installed the old sending unit and took it for a short ride and within 5 miles the OP light was on and then the "LOW OIL PRESSURE" message came on right away but the mechanical gage was still showing 12-15 lbs of pressure.

So tomorrow I'm going to put the new AC Delco sending unit back in and change out the Rotella for some Valvoline 10W30 and see what happens. I'm guessing that I'm still going to get the OP light but no "LOW OIL PRESSURE" message and the mechanical gage will still show 12-15 lbs of pressure.

I would really like to know if the flickering I'm seeing on the mechanical gage is normal for these engines and if not what could be causing it.

I'm about ready to pull the oil pump out and replace it.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #6
Re: Oil pressure light on at idle.

Because the PCM thinks you lost oil pressure.
Ranger,
I am NOT getting the LOW OIL PRESSURE" message with the light on but showing 12-15 lbs on the mechanical gage. That is what's confusing me. It's like the sending unit thinks there is low oil pressure but the PCM knows better and is not displaying the "LOW OIL PRESSURE" message.

Can you tell me if 12-15 lbs at hot idle is normal for a N* or is it low?
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

Northstar engine, GM/Cadillac service manual:

Hot engine - minimum pressure at idle - 5 psi. Minimum pressure at 2000 rpm - 35 psi.

Using Pennzoil Platinum synthetic 5W-30 my 2002, hot, idles at about 24 psi and stays at just above 45 psi above 45 mph or so.

If the mechanical gauge is jumping 5 psi, then something's not right - even an undamped oil pressure gauge needle should be awfully steady from idle to full redline. Oil "pressure" is a steady "flow", not subject to pulses unless there's a cyclic internal leak somewhere.

Ford likes slightly higher pressures ........... shimming the Northstar oil pressure regulator spring .006" will raise pressure about 5 psi above 2000 rpm hot.​ Shimming makes little or no difference at idle speeds. The small, custom-made shim goes in the pressure regulator spring cap - to exert a bit more pressure on the plunger by barely pre-compressing the spring.
 

Attachments

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

What oil filter are you using? Try a WIX 51522 or the NAPA Gold equivalent.
 

·
Super Moderator
Joined
·
86,145 Posts
Re: Oil pressure light on at idle.

Yeah, Sub is right, the FSM calls for a min of 5 psi at idle so your 12-15 should be no problem.

After going back and reading this from post #1 it's pretty evident that the pressure switch is not the problem.

Since you are good enough to do a HG & bearing job :)worship:), I'm sure you are aware of how critical the balancer torque is, but it almost sounds like the pump is slipping just a tad. Might be worth retorqeuing that sucker before going through all the work of pulling it.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #10
Re: Oil pressure light on at idle.

Sub,
I'm using an AC Filter. All my vehicles take the same filter and I ran into a sale on them so I bought 4. I usually use Purolater or NAPA filters. So I put the AC Delco sending unit back in and replaced the AC filter with a NAPA filter and now the gage fluttering is pretty much gone. Took it on a 15 min drive with AC running and no OP light and hot idle its running at a stable 12-15 lbs and at 2000 RPM its a stable 50 lbs. So apparently the sending units didn't like the OP fluttering at idle that apparently the AC filter was causing somehow??????

I still would like to see better OP at idle. Wish I had just replaced the pump when I had it apart but it looked good and only had 74K miles on it.

Ranger,
I know the balancer bolt is torqued correctly, actually it's over torqued a bit because the FSM has a typo in the installation instructions. It says 37 ft lbs plus 150 degrees but in the front of the book for all fastener torque specs it says 37 plus 120 degrees so it's got and extra 30 degrees of torque.
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

12 - 15 psi is perfectly normal for a passenger car engine warm/hot idle. Don't sweat it, and don't use heavier oils or snake oils. You're good to go.

Pressure is NOT lubrication - flow is.

Edit: My tricked out marine Olds 455 engines run 15 - 20 psi at an idle speed of 650 rpm using Pennzoil 15W-40 Long Life commercial duty conventional and Melling high output oil pumps.
 

Attachments

·
Super Moderator
Joined
·
86,145 Posts
Re: Oil pressure light on at idle.

I agree with Sub. Here is an article that should make you rest a little easier. It kind of brought the whole pressure thing into perspective for me. While I am sure none of this is new to you, it is still interesting and the 10psi/1000 RPM rule of thumb puts you right in the ball park.
http://kennedysdynotune.com/oil-pressure-tech/
And another.
http://www.boosttown.com/engine/oil_pressure_vs_flow.php

As for the change of filter settling things down, that was a big surprise to me, especially being an A/C Delco filter, but you can't argue with success.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #13
Re: Oil pressure light on at idle.

As for the change of filter settling things down, that was a big surprise to me, especially being an A/C Delco filter, but you can't argue with success.
I thought so too but then I started researching it this morning and found the following online.

http://www.silveradosierra.com/vortec-5-3l-v8/oil-pressure-issue-oil-filter-the-cause-t413073.html

Seems the AC filters with an "E" suffix on the end of the part number there is something different about them that has been causing low oil pressure problems. The filters I bought were PF61E's and I had used 2 in a row and that's when my issues started was with the 1st one.

Going to open up this last one and see if I can see what's going on inside.
 

·
Super Moderator
Joined
·
86,145 Posts
Re: Oil pressure light on at idle.

WOW! Thanks for that info Samert. I've been using those filters as well. I think I'll switch over to Purolator. Please post your findings. "Inquiring minds want to know".
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

Here's a bit more homework - notice the change to the AC Delco E-core - made by Champion which makes filters for everyone. (except Purolator and WIX)(It appears that Purolator rebrands for a few names also).

WIX used to be made by Dana Corp. (DANA Controls) but is now made by Affinia in ? Kentucky ? and is the same as NAPA Gold and PartsMaster.

http://www.minimopar.net/oilfilters/index.html

Click on the Opinions and Recommendations tab in the header and read the assessment of the E-Core filter arrangement ...........
 

·
Registered
Joined
·
282 Posts
Discussion Starter #16
Re: Oil pressure light on at idle.

Just finished dissecting 2 new unused filters. The AC PF61E and the NAPA ProSelect 21522 which I think is their Silver brand, both are for the same applications.

The AC filter has the plastic frame inside the filter media and is wide open compared to the typical metal sleeves with holes in it you see in most filters so I don't see any flow issues there. The AC filter media is .028" thick as measure with a micrometer with a friction thimble and is 48" long when stretched out. It has 61 pleats. Glued on each end of the filter media is a felt type of material and it had the typical stamped spring plate in the bottom of the filter and the typical rubber type anti drain back valve on top of the filter media.
DSC02037.JPG

The NAPA filter has the typical metal tube inside the filter media. The filter media is .020" thick and is 55" long when stretched out and has 46 pleats. Glued onto each end of the filter media are metal end caps and there is an actual spring in the bottom of the bottom of the filter and the typical rubber anti drain back valve on top of the filter media.
DSC02038.JPG

Here is a side by side photo of both filter media in their respective cans with their ID tubes in place with a rubber band compressing the media to the ID tubes like they are assembled. NAPA on the left and AC on the right. I had to double wrap the rubber band on the AC media to fully compress it. Note that the pleats on the AC filter are not as long as the NAPA. That along with the thicker media makes it a much denser media for the oil to flow thru.
DSC02040.JPG

It seems to me that the AC filter is going to flow less oil thru the filtering media than the NAPA filter and I think what was happening in my case was that at operating temp and at idle the AC filter could not filter enough oil to keep the bypass in the filter housing from opening and closing rapidly which is what was causing my fluttering condition which the OP sensor didn't like. Which means that alot more unfiltered oil is bypassing the filter. What I don't know is if that bypassed oil goes back to the inlet side of the filter housing or is fed to the engine bearings. If it not going to the engine bearings then they were probably getting starved of lubrication. I hope its bypassed to the engine, otherwise my new bearings may be compromised.
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

An oil filter internal bypass sends the oil straight to the engine oil galleries - the oil flows past the media, through the bypass valve, and out the center tube - straight to the engine. If the AC filter bypass was chattering then it would cause gauge fluctuation.

In ANY filter we're not filtering chunks - we're filtering microscopic particles and some soot. If the engine runs a bearing or sheds piston parts any oil filter isn't going to save it.

In cold weather almost 100% of the oil is bypassed until the engine/oil warms up enough to flow through the media. Normal. No damage done.

It appears that the WIX/NAPA filter has about 60% more media filter area than the Champion/AC unit.
 

·
-Administrator- 2002.5 F55 STS 2014 FWD Explorer
Joined
·
66,593 Posts
Re: Oil pressure light on at idle.

......... an old engine builder trick is to, at the first oil/filter change after new or repairs, open the filter, remove the media, squash sections of 8 or 10 pleats in a vise - this dries the media and you can accordion it open in sections to see what's trapped in the folds. Just remember that oil flows from the outer case to the inner tube.

samert, I took the liberty of updating the thread title, given its changes in direction.
 

·
Registered
Joined
·
167 Posts
Well, I have the same problem as samert at first post of this thread. Outside temp around 25 - 27 degrees (Celsius), car driven around 30 minutes and OP light started flickering at idle. Then, as time passes by, you have to increase revs to keep light off, finished (after another 30 - 40 minutes of driving) at 1000 revs. Below it lights up (and reading "Oil pressure low...").
Next day it started from the same point exactly the same - after 30 minutes light on at idle, then it become worse and finished at 1000 revs after around 40 minutes of city driving (so I have to stop at traffic lights, etc...).
Oil is new, Petro Canada 10W30, oil filter Fram PH3675.
Someone tells me that it means bearings are gone, someone tells it will be bad pressure sensor... Car has an oil cooler.
 

·
Registered
Joined
·
282 Posts
Discussion Starter #20
Since your car has the oil cooler it's not as easy to install a mechanical pressure gage in the oil filter adapter using 1 of the cooler ports but could be done with a pipe thread tee to see what your oil pressure actually is. It sounds like you just changed your oil and this problem cropped up? If so then I suspect that may have something to do with with your issue and would suspect a problem with the oil filter especially if this is the 1st time using the Fram Extra Guard brand. If that is the case then the easiest test to rule the filter out would be to change it out with a NAPA Gold filter which is what solved my issue. I had just switched over to an AC filter and it was causing my oil pressure to flutter at idle and the pressure switch did not like that at all once the car warmed up.

If changing the filter brand does not correct your problem then the best thing to do is install a mechanical gage to see exactly what you oil pressure is at idle when warm. If at idle you have at least 10 PSi then changing the oil pressure switch would be my next move. 6 PSi is what the switch is suppose to activate at and 10 PSI should be plenty to keep it from activating. Make sure you install an AC Delco switch as some of the aftermarket switches are not calibrated very good.

Get back to us on what you find.
 
1 - 20 of 57 Posts
Top