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OT: Is my oil pressure gauge an idiot light in disguise?

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  • OT: Is my oil pressure gauge an idiot light in disguise?

    I've got a 2000 Silverado with the 4.8L engine. The oil pressure has always read just under 60psi whenever the engine is running. It DOES move about a needle width up or down in response to changes in engine temperature and speed.

    I noticed quite a bit of oil pressure variation on the other cars I've driven recently that had gauges. Most would be around 30psi at idle, and go up to 60+psi at highway speeds. They'd read higher when the engine was cold.

    Why would the Silverado have such consistent oil pressure when other engines vary all over the gauge as conditions change? The small changes I see suggest it's really reading pressure, but is it really an idiot light in disguise?

    Roger
    Any products mentioned in my posts have been endorsed by their manufacturer.

  • #2
    Originally posted by winchman
    I've got a 2000 Silverado with the 4.8L engine. The oil pressure has always read just under 60psi whenever the engine is running. It DOES move about a needle width up or down in response to changes in engine temperature and speed.

    I noticed quite a bit of oil pressure variation on the other cars I've driven recently that had gauges. Most would be around 30psi at idle, and go up to 60+psi at highway speeds. They'd read higher when the engine was cold.

    Why would the Silverado have such consistent oil pressure when other engines vary all over the gauge as conditions change? The small changes I see suggest it's really reading pressure, but is it really an idiot light in disguise?

    Roger
    Check it again in 10 years. It will read lower.

    Comment


    • #3
      Just a guess, but maybe if the engine is tight not too much oil is bypassed through play in bushings, etc. In that case the regulator on the oil pump may be operating in a better range. When more oil passes through the engine parts, the regulatir won't be bypassing as much oil internally so it probably allows more variation in oil pressure. The gauge, if it's working properly, will show this. I don't know if the gauges themselves go bad, but maybe they do contribute to the changes in readings.

      I suppose it's possible that a particular engine would have a higher volume oil pump by design to ensure that even when the oil is hot, the engine is worn, or is run at low speeds, there will always be a reserve oil pumping capacity to keep the engine fully lubed. In this case, most of the oil pumped would be bypassed around the pump, and the minimum amount the engine is using doesn't represent much of a change to the oil pressure regulator. In this case the gauge wouldn't fluctuate much at all.

      Just a few thoughts.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        A quick check of the automotive forums suggests that problems with the oil pressure sensor are common. The gauge will either read high all the time or will drop to zero when the engine warms up.
        Free software for calculating bolt circles and similar: Click Here

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        • #5
          Modern gauge clusters are, indeed, little more than glorified idiot lights.

          The fuel-level gauge, for example, has been 'dampened' almost since it's inception. If it read direct, the needle would sway erratically due to the fuel sloshing in the tank. So the gauge is "damped" to the point it takes many seconds for the needle to react to a level change.

          More recently, they've added- or increased- the damping to the others as well, the oil pressure especially. People would see the gauge read high when cold, then drop alarmingly when the engine warmed up, and then vary considerably as the engine speed or load changed. They'd bring the car back to the dealer and complain of varying oil pressure, and demand it be "fixed".

          Ditto the water temperature- the average motorist, assuming he or she pays any attention to the gauges at all, wants to see that needle in the same place, each day, all day, every day. Doesn't matter whether it's 104 in the shade or twenty below- if the needle's not where the owner thinks it should be, he runs it back to the dealer and demands they fix it.

          People have written whole books on the subject. Literally.

          So today, generally, the only gauges the motorist really pays attention to are the gas gauge and the speedo- most often in that order.

          All the other gauges are simply idiot lights with a needle- the needle is designed to point to the middle of the range unless the value falls below a set point, at which time the needle moves considerably, in order to attract attention.

          If you want true direct-reading gauges, you'll have to install an aftermarket set- and preferably mechanical ones. I'll bet if you do so, your "60 psi" will turn out to be about 30, probably dropping to the high teens, low twenties at idle.

          Doc.
          Doc's Machine. (Probably not what you expect.)

          Comment


          • #6

            What I put in my old el Camino when the idiot light "switch" died. I was afraid to drive it for a few days till I could get this mechanical guage in. I still have to hook the probe up in the head there on the left, drain some coolant, install.

            Some vehicles the gauges are tied to the computer, the actual sensor tied to the computer also.. I remember something doing the gauge bang-biff-bang as a indicator for "something"?? perhaps it was the old Ford Taurus we had for a while?? It also had the ac compressor and other things computer controlled.

            (mine is running 60 at idle.. does not increase with rpm, the spring-bleed off is right there, new engine with less than 100 miles) No idea what kind of pump this engine has in it. I have not even been able to paint it from Raw clean metal yet..

            I can remember while building the engine for the old tattoo bus, (I was drinking) I not only knocked out the carter key, but put a washer and stretched the bypass spring on the pump. When I cranked it, it pegged at 100psi, the oil filter split down the side.. I thought it was blowed for a moment.. I had to run a special "thick" wall oil filter made for stock cars ($32.50) I got snookered out of my bus by a band group-preacher with a promise, trusting devil that I am.. I didn't even look under his trader van.. it had the motor "chained in" sitting on 2x4 blocks to secure the broken motor mounts..

            Later I remember seeing the mini bus with a oil "path" in behind it. Never saw it on the road again.. I had forgotten to tell him about he special oil filter it required.
            Last edited by Dawai; 07-21-2009, 08:45 AM.
            Excuse me, I farted.

            Comment


            • #7
              Winchman, Do you have a manual transmission?
              If so load the engine down to about 600 rpm's and check the results when warm, You should see a difference at this rpm, You just might have some very good news, you might have an engine that's holding pressure very well,
              On the old volkswagons with the idiot lights it's a way me and my bro used to rough guess the engines internals --- first check them cold by shutting off the engine and then just turning the ign. switch back on and count the seconds till the light appears, then with a warm engine we would load the engine below idle, some would have a flickering light - some would remain off, When you had a warm engine that you would have to turn off and then turn the switch back on and count to 3 seconds you were fairly sure you had a tight one (rods and mains cam bearings lifters and oil pump)
              This was a good test in one direction as its tough to be fooled by a sender unit with zero pressure otherwise it would remain off all the time --- but on the flip side, the engines that would flash early were not a guarantee to be worn out, Many senders had way to high of a rating and triggered early, we had a test sender we knew was good and would swap it out -- if the light triggered early after that we knew we had what we called a "bleeder"...

              Gauges are tougher due to the time delay but there are methods -- If you have an automatic trans and cant load the engine then just pull the ECU fuse and crank without starting -- this is low enough speed that with a warm engine you should get the proof you need that your gauge is indeed covering the range and not just some kind of needle that's getting hung up in the middle...

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              • #8
                I don't know about Chevy but Ford Rangers that have an oil pressure gauge have an oil pressure SWITCH that an idiot light would use rather than an oil pressure sender. There is a resistor across the terminals on the back of the gauge to make the gauge read the same thing all the time. Ford did it because of oil pressure complaints of low oil pressure at idle. You can fix it by replacing the switch sender with a pressure sender and cutting the resistor out but you have to remove the instrument panel and not many are willing to do that. I'm sure Ford does the same on the rest of their models of cars.

                Maybe Chevy does the same thing now. If the gauge is reading real oil pressure the gauge should show a pressure swing, not stay in one place.

                Thanks to the idiots in the world we have idiot gauges. Manufacturers want to make the customers happy.
                It's only ink and paper

                Comment


                • #9
                  I think you have a legitimate problem.

                  I have a 2000 S10, and the oil pressure gage does the normal 35 at idle, 60 at speed thing that you'd expect. The temperature gage and the voltmeter also do what would be expected.

                  Evidently, despite the gloom and doom crew here, the 2000 model year Chevy still had legitimate gages, at least on some models.

                  BTW, I don't have any clue why it would be a BAD thing for the gas gage to be 'damped" so that it does not hiccup and bounce every time you drive over a piece of parakeet poop. It is much more useful when it reads the average than if it swings wildly from full to empty. Otherwise you ahve to guess what the real reading is. I remember those days, when you had to do a "visual average" to arrive at the reading.....
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Originally posted by Doc Nickel
                    - the needle is designed to point to the middle of the range unless the value falls below a set point, at which time the needle moves considerably, in order to attract attention.
                    In the case of some Toyota cooling system gauges they sit just below half way on the gauge through a wide range of hotter temperatures and then move suddenly if the engine overheats. By that time it's too late and the engine is cooked. This is why a low coolant alarm is a good thing to install. Early warning of coolant loss long before the gauge moves.

                    Nev
                    Nev.

                    Comment


                    • #11
                      The gauge on the Silverado is supposed to read like a regular oil pressure gauge. It isn't an "idiot gauge". The problem is most likely the sensor since that matches the description of many similar problems on a variety of forums.
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                      • #12
                        bad thing ..
                        my fuel gauge reads/ remembers/ stays there ....even with the batt disconnected .

                        so all the fuel thief would have to do is have a look at your dials to see if you had a full tank............same with the thief who wants to steal the car...like this in all rovers made after a certain date.

                        all the best.markj

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                        • #13
                          So put a switch across the sender and leave the sender open/shorted (which ever suits) except when you need to read the fuel level.
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                          • #14
                            I had a problem with an 84 Chevy truck. The dealer, no less, changed the sender for about $35. That was some years ago, but even at today's prices, I would imagine you could do it yourself for under $30, a good mechanic for under $50, or a dealer for under $75. It's an easy job on most engines - a lot like changing a spark plug.

                            If the gauge is reading when running and returns to zero when off (it moves across 1/3 to 1/2 of the scale), then the gauge itself is probably OK. If the wiring was bad, it would either not work or jump all over the place. Could be a computer/electronic problem, but senders are a lot cheaper so I would try that first.

                            Just replace the sender and see what happens.
                            Paul A.
                            SE Texas

                            Make it fit.
                            You can't win and there is a penalty for trying!

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                            • #15
                              Originally posted by Evan
                              So put a switch across the sender and leave the sender open/shorted (which ever suits) except when you need to read the fuel level.
                              Ive only got two gallons in the tank most of the time ..'cause I'm on LPG ..so don't matter much to me ...

                              all the best.markj

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