Oil pressure problem

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by 90burban, Aug 15, 2013.

  1. 90burban

    90burban New Member

    I have a 1990 gmc suburban, 112000 with a remanufactured motor from jasper with around 3000 miles on it. I have had no problems until I changed the oil with a k&n filter and 10w30 oil and now the oil pressure gauge stays at 60 while driving and even right after start up. I changed the oil again with 5w30 and a purolator filter and it still stays that way until I drive it for a while then only while idling will it go to as low as 30-40 but once I give it gas it shoots right up to 60 and sometimes it will go above 60 and that's maxing the gauge out, before it would stay around 30-50 and rarely go near 60. It does not run any different, should I be concerned or is this normal.
  2. mwa3c

    mwa3c New Member

    Hi 90Burban!
    I have a 1999 GMC 1500 with a 350. I put Mobile1 synthetic in my engine after i bought it and exibited the SAME results you are seeing on your truck.

    After reading around, this is farily normal for this truck. The pick-up sensor is well after the oil filter, so the "higher than normal" pressure you see indicates that the oil is flowing past the pump, past the filter, and hitting the upper galley the way it should.

    On my truck, after driving around for about 15 to 20 minutes, the pressure gage drops back down to 30 to 35 ish at idol and upper 40's during driving. But, when the oil is cold (less than 20 minutes run time) the gage stays up around 60psf.

    If you went from conventional oil to synthetic, and suddenly see the increase, the general assumption is the synthetic "flows" better through the filter, allowing the "full pressure" to reach the upper engine area.

    I had the SAME Panic attack you did, but then realized I saw the SAME condition on my 1987 IROC Z years ago when i switched to synthetic oil.

    Your fine :) enjoy the "freely flowing oil!"
  3. stchman

    stchman Active Member 2 Years 1000 Posts

    IIRC, in 1999 the GMC and Chevrolet pickups were re-designed (GMT800 replaced the GMT400) and the 5.7L engine was replaced by the 5.3L engine.
  4. mwa3c

    mwa3c New Member

    Beg to differ. 5.7L is firmly planted under the hood of my extended body 1500 4x4. Maybe AFTER 1999 they went to a 5.3L?

    There is a HUGE difference in my Spider injected Throtle body driven 5.7L than the 5.3 MPI systems.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    The GTM800 Silverado/Sierra 1500 (light pickup trucks) were released in 1998 as 1999 Models. The "classic" light-duty GTM400 C/K Trucks were continued in production for that first year alongside the new GTM800 Models, and the Heavy-Duty GMT400 pickups (alongside the GMT400 SUV's) were continued through 2000, with the new GMT800 Silverado/Sierra HD (Heavy Duty) introduced in 2001.
  6. stchman

    stchman Active Member 2 Years 1000 Posts

    So the GMT400 was produced in 1999 as well alongside the GMT800. This is similar to the 2007 GMT900 and 2007 classic GMT800.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor


    This is why it is important, when a Member has either a....1999" or 2007" Chevy or GMC Light Duty Truck, and does not have a Picture of their Truck in their SIG.....to let Us"the members"know which Model Truck they have, so we can give them the Best Advice and/or Help with their Truck.
  8. mwa3c

    mwa3c New Member

    I don't think I understand what point you two are trying to make here. The originial post had a 1990 Suburban and mine is similar. In addition, the engine in both trucks essentially are the same minus fuel injection systems.

    So why the poking fun?

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    I was not poking fun, the Point I was expressing to Stchman, as I mentioned, that there Were 2-Different Models of Chevy/GMC Light Duty Trucks, that could have been bought back in 99" and in 2007"......and when Member's have one of these 2-years of Trucks "a 99"or 07", and they are asking for Help and/or Advice regarding their Truck, and beyond the year, If we "the Member's" don't know what Model Truck they have, we can't give them the Best Advice and/or Help, in answering their Question/Question's.....as the 2-Models of 99"s and 07"s have different Issue's and/or Problems.

  10. stchman

    stchman Active Member 2 Years 1000 Posts

    It's called clarification. Since you could get either a GMT400 or GMT800 in 1999, it is important that if someone is asking for help, that they clarify.

    As far as the same engine, the GMT400 has a 5.7L with TBI and the GMT800 has a 5.3L with MPI. Tell me again how those engines are essentially the same?

Share This Page

Newest Gallery Photos