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Possesed Oil Pressure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Apr 25, 2001.

  1. Sparky

    Sparky 1/2 ton status

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    My trucks moter is showing some age. When I fire it up it runs up around 60-70 psi. When I drive it on the highway for an extended period (more than 10 or 15 min.) the oil pressure start doing strange things. Around 70 mph and 3000 rpm the oil pressure will start to jump without a change in speed or pedal. It will bounce slowly back and forth between 45 and 25 psi. The faster I go the larger the changes, and the lower the pressure gets. Sometimes it will jump to 20 psi at 3500 rpm. At idle it has a little under 10psi in gear (600 rpm) and about 12 or 13 in neutral(750 rpm). The 350 does not burn a drop of oil and it runs clean and well (passes 97 year emisson testing without a lick of smog equipment). What would cause this to happen? Just worn bearings, or something else? Anyone else had this problem? The number should be acurate as they came from two different mechanical gages.

    Sparky

    When all else fails... Check the blinker fluid.
    78 K-5
     
  2. muddin4fun

    muddin4fun 3/4 ton status

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    Maybe you got some junk floating around your motor or in the sending unit. Run some Marvel mystery oil in your crank case and replace the sending unit. That's what I would start with.

    [​IMG]
    <A target="_blank" HREF=http://k5chevyblazer.homestead.com/home.html>http://k5chevyblazer.homestead.com/home.html</A>
     
  3. Sparky

    Sparky 1/2 ton status

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    There is not junk in there. I have had the oil pan and valve covers off too many times since it started for that. All is clean. And I dont have a sending unit. Its mechanical.

    Sparky

    When all else fails... Check the blinker fluid.
    78 K-5
     
  4. Pugsley

    Pugsley 1/2 ton status

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    try checking your gauge - There could be something occluding the Bourdon tube, causing it to be erratic.

    [​IMG]
     
  5. jimmyjack

    jimmyjack 1/2 ton status

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    could be fluctuations with the oil draining from the motor back into the pan. Check to see if the drains in your heads are clear of sludge. 'Specially near the rear of the motor. Sounds kind of far fetched but you never know. I met a super mechanic from Mars years ago(this guy was a freak) I was having problems with smoke, figured my rings were toast. He cleaned out the oil drain holes and it never smoked again. I complained about my gas mileage. He listened to the motor and told me to change my battery, it was dead. I blew it off, 2 days later it died, I bought a new one and my milage picked up. Wish I could find him again!!!.

    "My blazer may be slow, but it goes faster at higher speeds"

    Jim
     
  6. Eagle86K5

    Eagle86K5 1/2 ton status

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    I recently replaced the intake with a high rise and the same problems you are experiencing started. I found that the wire to the sending unit had come loose...causing the erratic readings. I just tightned it down and the problem dissappeared.
     
  7. behemoth

    behemoth 1/2 ton status

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    ..".Marvel Mystery Oil" ????? Please explain! I'm having similar problems w/oil pressure.

    behemoth K5
    "Better to remain silent and be thought a fool -
    than to open your mouth and remove all doubt"
     
  8. jarheadk5

    jarheadk5 1/2 ton status

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    On my 87 305 with the stock electric gauge, I've NEVER had oil pressure below 30psi. Of course, if I tap on the gauge lens, the reading changes drastically. So I'm installing Autometer gauges now.

    [​IMG] Semper Maintenance!
     
  9. muddin4fun

    muddin4fun 3/4 ton status

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    you can put it in your crank case and it will clean the bottom of your moter. you can put it in the gas tank and it will clean the top half of the motor. It's great stuff! If your oil pressure is going crazy, then chances are it needs to be replace though. i would run that marvel stuff and then replace the sending unit.

    [​IMG]
    <A target="_blank" HREF=http://k5chevyblazer.homestead.com/home.html>http://k5chevyblazer.homestead.com/home.html</A>
     

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