Why does my oil pressure bottom out when there is no leak?

40

Asked by Nov 26, 2012 at 02:55 PM about the 2001 Chevrolet Suburban LT 1500

Question type: Maintenance & Repair

I have a 2001 Chevrolet Suburban 1500 with 232k miles.  Although it burns a little oil, it does not leak.  The oil pressure regularly fluctuates and bottoms out when idling.  But, when the RPMs go up, so does the pressure.  Eventually the pressure stays up.  The next time I start the car, however, the pressure may stay up or begin fluctuate again.

27 Answers

80

I am borrowing a 1998 GMC Suburban 1500 & it does almost the exact same thing to me - both fuel & oil gauge. I've replaced the oil pressure sensor ($40 part) & no difference. Did a diagnostic on the veh - found the fuel level to be registering less than the gauge was reading. I believe my issue is the gauge cluster. I will say this though - timely oil changes seem to be the greatest deal of help. You may want to check that oil pressure sensor - as it's an inexpensive part. Also, many parts shops will run a free diagnostics on your vehicle. If your issue is a cluster - those are about $250 from a junk yard...give or take. Good luck!

8 out of 8 people think this is helpful.
16,225

This is normal for anything with alot of miles on it. Leaking oil and oil pressure dont impact anything unless you leak all of it out. An old oil pump or engine can have oil pressure drop at idle to next to nothing. In reality most engines can run off of 5psi saftly. As long as the check gauges light doesnt come on and there is no knocking its ok.

9 out of 9 people think this is helpful.
6,425

at that age there could be sludge in the pump intake. if it gets into the 25-66 PSI when warm & running, it will be ok. how does the engine sound at idle?

5 out of 5 people think this is helpful.
16,225

I just read what i posted and I had some typos. Oil leaks and pressure dont impact each other. And engines can IDLE off 5 psi saftly, some even less. But like jason said, when the rpms increase it needs to go back up. Lesson I have learned is I cant type if i havent slept in 24 hours...

8 out of 8 people think this is helpful.
40

I've replaced the oil pressure sensor with no change. So, while something tells me that its still electrical, I'm leaning more toward the sludge answer. This morning, as many mornings, there was no issue with the oil pressure. So either sludge or trash or something is fouling the spring in the pump or something is blocking it at low RPMs, but only sometimes. Very frustrating, because to replace the pump means taking the whole #%@&^ thing apart.

4 out of 4 people think this is helpful.
16,225

pressure will be higher when oil is cold. I've had many vehicles do this. Domestic, import, doesnt matter. When cold oil pressure looks fine, even after warmed up it's still may not drop lower than 10 psi at idle. But after i take a 25 mile highway trip when it idles it's next to 0 psi, but will jump back up if i rev it or as i start accelerating. All this is due to the oil warming up and becoming thinner, and is normal. It is a misconception that you need gobs of oil pressure at idle. It certainly doesnt hurt, but isnt needed. Minimum oil pressure for a chevy 5.3 is 6psi at 1000 rpm. Here's a hint, idle is LOWER than 1000 rpm so at idle its lower than 6 psi. Only consider fixing it if you either hear knocking or pressure doesnt rise when rpm's increase. Other than that is just a waste of money. Also dont go get thicker oil as this will raise pressure but starve your lifters for oil. And i doubt there is an electrical issue, these sensors either work or dont. Even if the gauge doesnt read accuratly, the idiot light will illuminate if pressure drops to low regaurdless of gauge.

12 out of 12 people think this is helpful.
50

I am about to purchase an 07 tahoe with 131,000 miles on it. When I checked the vehicle yesterday i noticed that the oil gauge moved from dead center toward the right when I accelerated. Then it dropped back to dead center. Any thoughts ?

5 out of 5 people think this is helpful.
70

That's how it is supposed to react. The higher RPM will show HIGHER oil pressure, while driving or at idle. Obviously as the vehicle warms, you tend to lose a bit of oil pressure do to the warm oil being thinner. As the oil viscosity breaks down you also tend to lose oil pressure. Regular oil changes with non generic oil usually does wonders to raise your oil pressure a bit. My 1993 C1500 starts out with about 66 psi, but after running 15 - 20 minutes, it usually drops down to below 30, which is normal on older model vehicles, and newer models, depending on the mileage?

7 out of 7 people think this is helpful.
220

I have a 2005 yukon denali. I'm experiencing the same problem. Only thing is my oil pressure gauge stays at 0-5 psi. It occasionally rises all the way up then drop back down once I accelerate. Could this be a sensory issue or am I dealing with a different issue? Please help me

22 out of 22 people think this is helpful.
190

The oil pressure on my 2001 Suburban (210K miles), started rising this morning once I drove past 40 MPH. Also, I noticed that the engine was revving above normal when I gave it gas, but the speed was not increasing at the usual pace, almost like driving using lower gears. What can this possibly be? Engine temp was perfect

19 out of 19 people think this is helpful.
45

i have a 2003 subruban 2500 with low oil pressure (5-8psi)d that reacts to the throttle, once warm the pressure is fine and stays around 50-55 psi. changed the sensor with no help getting ready to change the oil pump and crankshft seal/bearing kit. truck is about to roll over 200k with the hig milage your crank shaft seal/s bearings are worn, as the motor warms up the seals/bearings expand enough to eliminate the oil pressure drop. oil pump change is just for reassurance against sludge and easy to do whith the engine out.

2 out of 2 people think this is helpful.
30

Just changed a lifter and now i have white smoke on start up in the morning.... Also when I start up oil pressure go straight to 40 then Hoover around 15 will a oil flush help or not before taking it to the shop pressure was fine

3 out of 3 people think this is helpful.
16,225

There is nothing wrong with that pressure as long as it goes up when you rev the motor

1 out of 1 people think this is helpful.
50

Sometimes a high mileage engine will have greater clearances in main and rod bearings resulting in low or fluctuating oil pressure at idle speeds. I once had a 350 Chevy engine that actually starved the lifters at idle speed. I simply upped the idle from 650 to about 850 and problem solved. Drove That old truck for another 8 years and sold it because I was moving. I still miss 'er!i

2 out of 2 people think this is helpful.
50

when its not crank the oil will not show on the dip stick an when it cranked up it shows the oil is ok

3 out of 3 people think this is helpful.
40

Dude you are a idiot low oil pressure is bad on your engine 5 psi is not enough here is the probable causes 1 your oil pickup is stopped up 2 wore out oil pump 3 your crankshaft Or crank bearing wore out 5 psi is not enough to keep your engine from blowing if you have a lot of miles I suggest heavy weight oil 20 50 check those three things and you can't go wrong

4 out of 4 people think this is helpful.
40

I have a 2000 Tahoe with 202,000 miles brand new alternator new radiator, a new oil pump and a new battery. My truck still not holding oil pressure and only did after pump was changed for 2days. I noticed my RPM's at a complete stop drop down to 500 or less . Im going to try the screen on the pressure sensors to remove but does anyone have any other suggestions or ideas ?

4 out of 4 people think this is helpful.
50

I have said this before: a high mileage engine can experience low oil pressure due to increased bearing clearances both in the rod and main bearings, although rod clearances normally increase before the mains simply because of the reciprocating action there. I would like to take this opportunity to say to Kevin, above that YOU sir, are the idiot. Your information is only partially correct, and you are in dire need of an attitude adjustment. Lilly, increase your IDLE speed just enough to prevent stalling. This makes a good temp. fix.

2 out of 2 people think this is helpful.
10

If you had the timing chains worked on or replaced. The chance guide's wares and when disturbed slowest the particulates to enter into the oil pan this will plug the pick-up tube. You my have to have the oil pump screen checked and flushed out. If you don't this will eventually cause the oil pump to fail and your engine will cease up. I know this because I experienced the same problem after having the timing chains and guide's replaced in mine.

1 out of 1 people think this is helpful.
150

Since last three months, I was facing oil pressure problem in my Chevy Suburban 2004 over 200,000 MI, the oil pressure needle was unstable and some time stuck at Zero with low oil pressure massage and warning sound, although engine was running stable without check engine light, I went to mechanic, he changed the oil sensor, cost me 50$ without solving the problem. Now he is saying it is a bad stepper motor of the oil gauge or bad electrical wiring. I asked him to remove the oil sensor wire which has resulted in zero oil pressure on the gauge with no ding dong disturbing low oil pressure message or check engine light and the engine is running very smoothly with out any unusual sounds. In my opinion, better way to test the bad oil sensor in GM vehicles is just remove the sensor wire and switch the ignition at on without starting the motor, if oil pressure gauge move to full at 80 in that case you have a bad oil pressure sending sensor and unfortunately, this test was not performed by my stupid mechanic before changing the good oil sensor.

4 out of 4 people think this is helpful.
150

For vehicles with an oil pressure gauge, the sending unit (located next to the oil filter) is essentially a variable path to ground for the gauge. When the engine is off, the sender is shorted to ground, and the gauge reads "0" psi (or close), as the oil pressure increases, the sender offers resistance to ground, providing a mid scale readings on the gauge. If the wire is removed altogether, the gauge will read off the scale to the high side (3:00 position) all the time. This is a quick and simple test you can perform to help isolate the problem. With the key ON - engine OFF, pull the wire off the sending unit. The gauge should read full scale. Now short the wire to ground (this will not harm anything), and it should read "0". If this is correct, then your gauge, and the wiring is good, and your trouble is likely to be the sending unit. If this test has little or no effect on the gauge, then your problem is in the wiring or the gauge itself.

6 out of 6 people think this is helpful.
50

In my never to be humble, old school opinion, you should remove all the silly electronic sensor devices and put in a regular old fashion pressure gauge, with a tempering orifice to calm down fluctuations of the needle (can be a little needle valve). This can be done by accessing the very back of the intake manifold, behind it and installing an 1/8 " npt nipple and connect tubing to that and a gauge. Or get an oil pressure gauge kit from a retailer and install that. They come with instructions and are much more reliable that the sensors. The gauges are kind'a cheap but you can put a small pressure gauge for about 10 bucks. I just screwed in the nipple to the block, some 5/16 fuel line hose w/hose clamp and ran it thru the firewall to the dash and the gauge w/another hose clamp. It may not be pretty but it works. And if you can't do it, and if your mechanic is any kind of mechanic at all, he or she can do it. If your mechanic is an idiot, find another one.

1 out of 1 people think this is helpful.

If your oil level is fluctuating and your engine light is on oil could be getting in to your catilac converter

10

DjjAvir i just had the same thing 4 weeks a go I did not check it out that day I thought it was low one gas my gauge had been to two years .so after adding gas it was Ok for a week the fuel pump when't out .$900.at a shop DIY. $150 look it up on rock auto.com.if you do it losses the breather by the tank it helps get it back in .use all gas befor you start and use a frinds car rack if you can .on a jack is hard but can be done [no the tire jack] I also have low oil psi when first stats up more so in cold weather an runs at 20 psi Hot but driving 30 - 40 for 3 years now and the light will come on under 800 Rpm. So some slug or needs new oil pump

1 out of 1 people think this is helpful.
10

One more thing this 5.3 now has 356000mi and have only replaced the water pump X2 and fuel pump X 4 do to last wife running low gas all the time the gas keeps the pump cool.i some one can tell me how to fix the low oil PSI i say thank you i am no motor head just passing on what i have seen

10

I own a 2001 Ford Explorer Sport Trac - At start-up, there is big clattering (and the gauge goes crazy) - but this all goes away after the truck warms up; highway driving or idling, no clattering. I just put in oil a couple days ago. I am thinking there is something wrong with my gauge - (it is simple and inexpensive to change it, so I will)... but anyone who has any help to share - please do. Could there be an oil pump problem? The oil is not low at all, in fact might be too full.

1 out of 1 people think this is helpful.
10

I have a '03 Yukon with a 5.3. My problem is actually the opposite.when idling oil pressure gauge is on 80. Once it warms up the gage drops to zero when I take off form a dead stop or if I hit passing gear. It jumps back up in just a few seconds. Is this the same issues as above?

1 out of 1 people think this is helpful.

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