GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 3 of 3
  1. #1

    Default Losing oil pressure drastically

    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. #2


    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...
    00 Chevy Tahoe LT, 5.3 4x4

  3. #3


    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.

    1996 Chevy Tahoe LT 5.7L V8 4X4 205,000+ miles. Built proudly at Janesville Assembly in Janesville, Wisconsin
    Basic mods: Lights all over, bunch of electrical work, and a couple cooling mods.

    Check out my other mods in My Garage:

Similar Threads

  1. Losing oil and coolant
    By ErolfPleiss in forum Chevy C/K Truck Forum
    Replies: 5
    Last: 03-01-2012, 09:30 PM
  2. losing oil in the yukon
    By Rob L. in forum GM Powertrain
    Replies: 5
    Last: 02-28-2011, 07:57 PM
  3. Losing power
    By aggie99 in forum GM Powertrain
    Replies: 0
    Last: 09-24-2009, 01:02 PM
  4. 2001 5.3...keeps losing fuel pressure
    By aftershock00 in forum General Chevy & GM Tech Questions
    Replies: 1
    Last: 09-03-2009, 03:44 PM
  5. Ford's losing $$$$
    By ChevyLover in forum The Coffee Shop ~ Chit Chat
    Replies: 1
    Last: 04-28-2006, 09:01 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts