Low oil pressure on 4.3 Vortec

Discussion in 'Engine Performance + Maintenance' started by stutaeng, Aug 12, 2019.

Car Parts
  1. stutaeng

    stutaeng Newbie

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    Hi guys, I need some help on a 99 Silverado with the 4.3. Over the winter I had noticed my oil pressure gauge on the dash was lower than normal. It is summer now and reading zero at idle when it's hot outside (100F, Dallas, TX)

    I hooked a mechanical gauge and it reads 6 psi at idle. There seems to no be a spec for idle pressure?

    I compared to Haynes manual at this is what I got:

    1000 RPM - 11 psi

    2000 RPM - 27 psi

    4000 RPM - 40 psi

    I have already replaced the oil pressure sender unit because the socket I bought for was machined wrong and I accidentally broke it trying to remove it.

    The truck has 250,000 miles and I've been running 5W-30 or 10W-30. I bought it with 87,000 miles and have mostly changed the oil when the light comes on. I just hear a small ticking, but no knocking. Seems like bearings are loose from wear and tear and was thinking to switch to 10W-40 or thicker.

    Back in February I did the intake manifold gasket and didn't change the oil right away. I covered the top of the engine with a plastic bag, but don't know if something got in there, or maybe it is just coincidence. I did see a residue on the oil plug the next time I changed the oil. Also, I have saved the oil filters since then, but have not opened them up.

    Any advice is welcomed...
     
  2. df2x4

    df2x4 Domestics only.

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    What light are you referring to? Neither of my '97s have any kind of an oil light, at least to my knowledge.
     
  3. stutaeng

    stutaeng Newbie

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    Oh, sorry, it's a NBS (GMT 800.) Engine is the same though as GMT400.
     
  4. stutaeng

    stutaeng Newbie

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    I also noticed that the needle on the mechanical gauge does not jump or is bouncy; it is steady.

    I switched to 20W-50 last night and got 10-14 psi at idle. No noticeable difference in engine sound or performance. I'll run this for a few weeks and we'll see what happens.
     
  5. Schurkey

    Schurkey I'm Awesome

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    Low oil pressure is a sign of problems. That said, there's no telling how long the thing will go even with abnrormally-low pressure.

    Hope for the best, prepare for a fresh engine.
     

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