What is your oil pressure? 1999 Suburban Vortec 5.7

Discussion in 'GM Diesel & DuraMax' started by jn1965, Jun 10, 2009.

  1. jn1965

    jn1965 Member

    I have a couple questions about the oilo pressure in your 199x Suburban with the 5.7 Vortec...

    The gauge always seems to read low to me. When she is cold the pressure till get to just below 40.

    Once she is warm, the idle pressure is at 19psi and when I am accelerating it gets to around 30psi.

    After a long highway run the pressure can drop to just above 0 and the 'check gauges' light will come on unless I give it some gas.

    I know this is not normal behavior, but the engine is running fine no misses, temps are below 200, etc.

    Since my gauge cluster is starting to get flaky I am wondering if this is just a symptom of faulty gauges (oil reading low) or if it could be a real problem, Has anybody had to change their oil pump on this engine?

    Has anybody tapped in a separate oil gauge? If so, where can I tap into?

    I started running 5w40 Turbodiesel Mobil 1, up from 5w30 gasser M1, and it seems to be helping (my other car is a Diesel)

    The engine only has 159k on it. has lots of power and is not blowing any smoke like it would if the rings or valve stem seals were worn out. She has only been given M1 since new and does not use any appreciable amount of oil between changes

    Thanks guys!
  2. jn1965

    jn1965 Member

    Wow nobody is having oil pressure gauge issues? Nobody has run a mechanical gauge off a Vortec 5.7?
    I find that hard to believe...
  3. BlackHawk99

    BlackHawk99 Member

    My 1997 Tahoe with 216,000 runs at ~41 lbs PSI hot and ~55 lbs cold based on the dash guage, if that helps...

    Never hooked up a mechanical guage to it.
  4. 97chevz71

    97chevz71 Rockstar ROTM Winner 100 Posts

    Mine runs about thirty when i am sitting and stop signs and lights.
  5. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    I would bet your gauge is OK.Your readings are not uncommon for an older motor.
    My 1998 210,000 Suburban reads 45 cold, but 21 psi at idle once warm.
    New motors usually are always above 40 psi.

    If your gauge was bad, I would expect it to be bad hot or cold.Your cold reading-40 psi-seems about right, SO THE LOW READINGS once hot are probably correct.

    Yes, the gauges can go bad, but I wouldn't bet your gauge is bad.

    Why not try 15w50 and see if all the reading go up. If they all go up, then it probably is just wear, not a bad gauge. 5W40 usually isn't the best oil because it has fewer lubricant molecules and more viscosity modifiers than 5 w 30.

    Try 15 50 and see if everything goes up-if it does your gauge is probably ok-and it is simply wear.
  6. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Mine runs around 45-50 cold then when she warms up and on the highway its around 30-35 and when idling after warm it can get down as far as 15, my mechanic says as long as there is no knocking or over heating it should be fine. If it starts to leak or use/burn oil then I would get really worried. After all its a 350 these can take a beating!!
  7. jn1965

    jn1965 Member

    I will try the 15w50 at my next oil change Is there a Mobile 1 in that weight? I have only used M1 from the beginning with this truck.

    On a funny note, The gauge seems to have settled down. My pressures are about 45 cold, just under 40 hot and about 19 at idle. The 'Check Gauges' light has not gone off since my original post. If I was stuck in bumper to bumper traffic the pressure would get low enough to trip the idiot light!

    Also my temps never exceed 210.
    Of course with the jittery gas gauge, I cannot be 100% sure of the accuracy of any of my gauges hence the idea of plumbing a mechanical gauge in at least for the short term...

    I agree that the 350 can take a lot of punishment. I just cannot see this kind of wear when the car has been run on M1 it's entire life and has been given oil changes every 4-5000 miles and does not burn a drop.
    I mean with only 159k it is barely broken in, right?:happy:
  8. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    what does your truck usually run at for temp?
  9. budfreak

    budfreak Rockstar

    My 97 truck with 350 vortech and 191K miles runs 45 psi cold and 20 psi hot when idling and holds about 35-40 when running down the road. I have a 30% higher flow water pump and my temp NEVER gets above 180 degrees.
  10. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Yes, there is 15W50 Mobil I- i USE IT IN MY MOTORCYCLES(it is car oil,I refuse to pay double for motorcycle oil). The 15w50 has red writing on it,I think.WalMart sells it now for about $22 five quarts.

    If your pressure is ok now- maybe it was just a wonky gauge? I would give the 15w50 a try anyway .

    I switched from the 5w30 to 10w30high mile oil.It didn't hurt my mpg and my warm idle pressure is maybe 22 psi instead of 20 psi.


    my 1998 has 210,000 runs great.

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