Jump to content
  • 0

1999 GMC sierra oil pressure guage reads erratic



Hi i own a 1999 gmc sierra with a 5.3l and automatic trans the truck has 199,000 miles and ive had no mechanical issues with it the whole life of the truck. There is one thing that does concern me approximately 50,000 miles ago the oil pressure guage started reading eratic at first it would just vibrate rapidly around its normal range it did that for awhile but now in the last 10,000 miles its still doing the rapid bouncing but now at idle it dips down to the 40 mark on the guage until the rpms are brought up then it comes up on the pressure reading. IIve heard that these engines had weak oil pumps? I dont know if thats true or not. Does this sound like a bad pump or guage or? Thanks for you time.

Link to comment
Share on other sites

7 answers to this question

Recommended Posts

i have a 99 gmc sierra. start it up, zero pressure. builds up to just over 40. as it warms up (also rev it up) it drops to zero. changed oil pressure sending unit. same problem. any ideas? that dont involve getting the pump out?

Verify the oil pressure with a mechanical gauge. If still at 0 or slow to build up, you're looking at a pump/pick up tube issue.

Link to comment
Share on other sites

199K & no issues? Well you'd better keep it! Stay away from the new ones. I've got 52k and lots of issues ...


But anyway - lots of the time the gauges (stepper motors), or the sender goes bad. Back in the day that was a GM trait on high mileage vehicles - the bouncy oil pressure gauge. Nowadays with all the shoddy components they use, you can't be 100% sure without testing. If your concerned with the oil pump I'd get a real gauge & hook it up to the block for a true reading - only then can you rule out the oil pump.

Link to comment
Share on other sites

These truck have bad oil pumps?Thats a first.Its your cluster mine does the same thing.As long as the oil pressure doesnt go below psi then i wouldnt worry.Some people say dont let it go below 10-15psi but i wouldnt let my trucks run without more then 20psi.

Link to comment
Share on other sites

Mine does this also. My gauge started reading quite a bit less all of a sudden, and erratically (sometimes you can watch the needle dance). Since the 99-02 stepper motors are usually trouble free I've always assumed it's the sending unit; it sure doesn't look like much fun to get to though.

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Forum Statistics

    Total Topics
    Total Posts
  • Member Statistics

    Total Members
    Most Online
    Newest Member
  • Who's Online   3 Members, 0 Anonymous, 657 Guests (See full list)

  • Create New...

Important Information

By using this site, you agree to our Terms of Use.