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1998 Deville
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Discussion Starter #1
Hi everyone.

I have a 1998 deville that had the oil light flicker intermittently in traffic, really only after along drive and when stopped. As soon as the rpms are over 800 it went away. Every once in a while i would get the "oil pressure low - stop engine" message.

I went ahead and replaced the pressure switch at the last oil change and all the messages went away, temporarily. Here we are a month and a half later and now every time i start the car for the first time in the day it immediately shows the oil light steady and has the stop engine message. If i let it sit for an hour and try to start, the message does not appear, the oil light stays out and everything seems fine.

I was going to hook a manual pressure gauge up to it and see what it shows.

My first question is; is there a place to hook up the analog pressure gauge other than where the the pressure switch hooks up? I am assuming you have to drain the oil in order to hook up the analog gauge up to where the pressure switch is and was hoping there was another oil pressure test location.

The other question is; what are the odds of the oil pressure switch going bad after a month in the car (ac delco replacement)?

The car makes no funny noises and runs great, i even had the oil fill cap off while running and could see oil splashing around inside the valve covers. Amazingly the car does not show any codes...
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,030 Posts
Unfortunately, the oil pressure sending switch (sensor, sender) location is the only place to plumb in a mechanical gauge. If I were to get antsy over actual pressures I would make up a flex hydraulic line from the sender location to ??? the radiator brace, install a brass T, and plumb in both the original sender and either a mechanical or electric gauge. Lots of work. There's a GM "special tool" that is nothing more than a mechanical gauge and length of flex hydraulic line with the proper sized male connector swaged on - you still have to remove the original sender and hook up the gauge..........you don't need to drain any oil.

The damn pressure senders on the Northstars are problematic - there always seems to be an active thread about them............
 

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1998 Deville
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15 Posts
Discussion Starter #3
That is a great idea. The sending units do seem to be a problem but most of the previous posts i have looked at seem like replacing the switch solves the problem. After looking i only see a few posts where the oil pump has actually gone bad on these cars. Tonight i will drain the oil and hook up the analog fill the oil and see what she says.

The only thing i can think of that i have done differently is when i did the oil change and replaced the switch i also put in a wix filter where in the past i usually have the oil done at joes garage where they use the cheap filters...
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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You don't need to drain any oil unless you want to do an oil/filter change at the same time. (The oil filter adapter is above the level in the oil pan.) You will get a couple of ounces of residual drainage from the passages.

I use WIX 51522 filters exclusively and 5W-30 synthetic and have never had an oil related message, even yesterday, in traffic, with an ambient air temp of 103 degrees (good ol' Baltimore).
 

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1998 Deville
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Discussion Starter #5
Interesting, I will try to do it without draining the oil. I had the filter off before when i changed the switch. Hopefully i can get to the switch without removing the filter. I remember it was pretty tight even with the filter off.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The filter adapter is held on by 2 bolts, and the face uses O-ring seals. You might be better off to just remove the entire adapter........
 

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1998 Deville
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Discussion Starter #7 (Edited)
So i finally got to hooking the analog pressure gauge up to the car.

43 psi @idle (700rpm)
74 @2000rpm

And as the engine warms up it falls to

12 psi @idle (650rpm)
50 psi @2000rpm

The service manual i have says minimum 5 psi @idle and minimum 35 psi @ 2000rpm

Are my numbers normal, it certainly has not fallen below either of the minimum pressures.

If so im going to just replace the switch again ($17.50 at dealership) and see what happens.
 

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1998 Deville
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Discussion Starter #8
Just checked the oil pressure again after letting the car sit overnight and the numbers are similar. This time though the initial oil pressure was 65 psi right after starting which is a little higher than yesterday.

Seems like the oil pump is all over the board as far as pressure but never seems to go below 10psi. Does this sound ok?
 

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2002 DTS, 70 Cougar conv, 2020 XT4
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833 Posts
As with almost all gas engines, as you probably know, the N* oil pump is direct drive, so the higher the rpm's the higher the pump speed and output pressure. It also varies somewhat with oil temp. Your readings aren't out of line.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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You're just fine - For time immemorial GM has liked a hot idle oil pressure of 15 - 20 psi, hot road (2000 rpm) of 40 - 45. Ford tends to like it a tad higher.

My marine Olds 455s run 25 psi HOT idle at 650 and 50 HOT at 2,000. Oil temps of about 220.

All normal...................and remember that the Northstar oil pump (as most others) has an internal pressure bypass set at about 60 - 65 psi to prevent blowing seals and gaskets during cold startup. Oil filters also have internal bypasses: they don't filter anything until the oil warms up...........

mchris........ Just for grins, what oil are you running ???
 

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White Diamond '03 DHS (with DTS floor shift)
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If I remember correctly our old Guru said that it only needs 3-5 psi at idle. I think the FSM confirms that if I remember correctly.
 

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1998 Deville
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Discussion Starter #12
Sorry for the late reply everyone. I have in fact solved the problem. I was about to permanently plumb in an analog guage and was disconneting the oil pressure switch when i noticed that the heat shielding around the wire to the oild pressure sending unit was brittle.

After reaching up and looking further it was painfully obvious that the problem was the sending unit's 2 wires were touching the exhaust manifold. unfortunately i could barely reach my had up in there so the solution was to put electrical tape over the exposed wires and put in new plastic heat shield and zip tie it away from the manifold. For future reference, it looks like the oil pressure sending units wires are not secured away from the manifold so i would think that this issue probably happens a lot...

http://i1227.photobucket.com/albums/ee424/mchrislincoln/photo1.jpg
 

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1997 Deville D'Elegance
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Hey mchris333,

I am having the same issue w/the low oil pressure light coming on intermittently. My car is in the shop now and they quoted $330 to replace the unit citing that the labor is a big chunk since the oil pressure sending unit is hard to get to. Does this seem normal/appropriate? How much does the sending unit itself cost? Thanks for any help you can provide!
 

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1997 Deville D'Elegance
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43 Posts
I just looked up the oil pressure switch price on rockauto.com and it's less than $10 for the switch...so that means $300 in labor!? Is this legit or am I getting played?
 

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White Diamond '03 DHS (with DTS floor shift)
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You are asking the same question in at least 3 different threads. I answered in two of the others.
 
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