Losing oil pressure drastically

Discussion in 'General Chevy & GM Tech Questions' started by Mrs Johnson, Sep 22, 2012.

  1. Mrs Johnson

    Mrs Johnson New Member

    The hubby and I recently gained possession of my mother's '99 GMC Sierra. It has the 454 big block 7.4, and while we were aware there was some motor issues, it wasn't until today that we had any SERIOUS problems out of it. We know the rings need replaced, and it burns oil/smokes and goes through plugs every few weeks. But today on my drive to my mother-in-law's, I noticed it started feeling a bit gutless. When the truck is running well, while rpms are up, it maintains about 60 psi, but when I noticed the change today, it'd dropped to 40 psi, and not 10 yards down the road, checked again as it started to sound a bit funny, and psi had already dropped to 20 psi. We THINK it may be the oil pump, but wouldn't such a part just go out completely, not gradually? Need a bit of help. This is our only ride at the moment. :/
  2. Kady

    Kady Epic Member 5+ Years GMTC Chick 100 Posts

    Might sound like a dumb question, but today, have you checked to see how much oil you have? My gauge would act funny when I was low on oil...
  3. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    The best fix is to find where the leaks are and fix them before a catastrophic failure that seizes the engine for good. Also if you know whats wrong you should fix it so the truck is back running in good condition. Btw oil pressure will vary with rpm, higher rpm equals higher pressure lower equals less, my Tahoe when idling runs about 20 psi but when driving and at speed runs about 40 psi and sometimes 60 when it first starts and the oil is thicker.

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