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oil pressure problem while driving

Discussion in 'Vortec 4.2L I-6' started by Erick1989, Nov 13, 2017.

  1. Erick1989

    Erick1989 Member

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    I have a 03 Chevy trailblazer 4.2L 6. I've had the oil pressure gauge jump up and down while idling. now it is going to zero while I'm driving and I can hear knocking so I know it's not a fake reading. should I replace my oil pressure switch and my oil pump and can anyone tell me the easiest way to get to oil pump please.
     
  2. Mooseman

    Mooseman Moderator

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    Knocking noise is truly indicative of an oiling problem so stop driving it until you can confirm/dispel an oil issue. You would need an oil pressure tester gauge.

    Replacing the oil pump is no trivial task, especially with a 4x4 truck, so confirm it is an actual issue with the pump or if it's possibly an internal engine failure causing the knocking. Replacing the pump is basically the same as replacing the timing chain so as a preview, here's a writeup on the job:
    How to replace I6 timing chain and tensioner
     
    Redbeard likes this.
  3. Erick1989

    Erick1989 Member

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    thank you very much for the info. is it worth bringing to a mechanic I usually do my own work but it's hard I had a back injury happen at work. I usually don't use mechanics unless I really need to what price range do you think it would cost for a shop to do a oil pump

    and also it only starts to knock when the oil gauge drops to zero with in gear and driving. I drove this morning around for a bit and it didn't happen till after driving it for about 15 mins.

    [Mod edit: Please use the edit button instead of double posting. Posts merged Thanks]
     
    Last edited by a moderator: Nov 13, 2017
  4. Mooseman

    Mooseman Moderator

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    You could have them do the diagnostics but to do the job, it wouldn't surprise me if it will cost over $1000 in labour alone.
     
  5. Redbeard

    Redbeard Well-Known Member

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    To see if any damage may have occurred you can send an oil sample to Blackstone Labs. (https://www.blackstone-labs.com/) I have used them for the past 15 years or so and they do a good job showing whats "floating" around in your oil. When some extra metals are in your oil they can give you a "heads up" as to where the metal may have come from in your engine. For me it would be a good peace of mind after I thought a oil pump died on me.
    from their website:
    Blackstone's standard analysis will tell you what you need to know about the condition of your engine and how it's wearing. The standard analysis costs $28.00 and includes the following:
    Spectral Exam: Establishes the levels of wear metals, silicon, and additives present in the oil. Also checks for coolant.
    Viscosity: Determines the grade of oil.
    Insolubles: Quantifies the percentage of solids present in the oil.
    Flashpoint: The flashpoint is the temperature at which the vapors from the oil ignite. When the flash is lower than it should be, it shows
    a contaminant (usually fuel) is present.
     
    Mooseman likes this.
  6. Reprise

    Reprise Silver Supporter

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    +1 on Blackstone; they'll send you a free collection kit (plastic bottle) if you go to their site.

    I'll be changing my oil in the next couple of days; once I get my initial analysis for the Envoy (couple weeks) I'll post a copy on GMT for reference.
     
    Redbeard likes this.
  7. Erick1989

    Erick1989 Member

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    thanks for all the help I figured it would be in that range because my father did a timing chain some years back on a small car no 4x4 and it was $700
     
  8. MRRSM

    MRRSM Gold Supporter

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    It is very likely that your 2002 SUV came with the Old Style Gerotor Oil Pump that featured a very shallow insert point for the Oil Pick Up tube where it mates up to the bottom of the Gerotor Oil Pump...bolted into the Timing Case Cover. Back then... what was happening involved either the complete flattening out of the Blue O-Ring... or cuts, nicks or tears that occurred in it when poorly installed when the motors were first assembled was causing a failure of the Oil Pump Pick-Up Tube to draw motor oil in from the bottom of the crankcase.

    The later versions of this pump featured a deeper extension of the tube and an "Orange Seal" that covered the entire bolt hole and flange and that holds the pick up tube inside of the newly designed pump. These Atlas engines can develop and require as much as 65 PSI of Oil Pressure that equates to moving 7 Quarts of Motor Oil from the crankcase throughout the engine at a rate of over 11 Gallons a Minute through the oiling system in order to allow the engine to stay alive and not seize up at nearly 6,000 RPM during shifts at speed.

    So with the wonky oil pressure readings you are getting, coupled with the very scary noises from inside of the motor at the same time... either the problem involves a clogged Oil Pick Up Tube causing oil starvation... or there could be a suction leak as described above that will prevent the Gerotor Oil Pump from pulling in enough oil and possibly having air cavitation as a result.

    Regardless of which of these is the case... unless you can take oil pressure readings via an Analog Oil Pressure Gauge and Copper Tube and Metric Adapter installed where the Oil Pressure Sending Unit is now located and prove that the engine is not starving for oil.... @Mooseman 's cogent advice should rule your actions about NOT running the engine until such a test can be done. The attached link and related images from my Photobucket support what is covered in this post and should give you much pause about how difficult the work will be to accomplish if you decide to do this job on your own:

    http://s557.photobucket.com/user/60...ENGINEREPAIR/GM42LOILPICKUPTUBE?sort=2&page=1
     
    Reprise likes this.
  9. Erick1989

    Erick1989 Member

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    so I brought my truck to a shop and we determined my problem is internal engine problems. I'm looking for a lower mileage engine to swap with mine which has 220k on it. Now should it be cheaper and make more sense to Rebuild the engine I have or do a engine swap with a warranted lower mileage engine ????
     
  10. Tiggerr

    Tiggerr Gold Supporter

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    I’d look for a low mileage used motor personally....
     
  11. Erick1989

    Erick1989 Member

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    Thanks Tiggerr already in the process of shopping around just seeing what was more sensible in the long run. Anyone know from experience what a mechanic would charge me for a engine swap just Labour. And about how many hours does this job take in total. thanks everyone for your guys help this is a great and very helpful forum.
     
  12. MRRSM

    MRRSM Gold Supporter

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    Last edited: Nov 17, 2017 at 10:19 AM

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