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  1. #1
    Jr. Apprentice
    Join Date
    Feb 2010
    Location
    Stroudsburg, PA
    Posts
    13

    Default Low oil pressure after intake gasket?!

    Hi all!
    I have a tech question following the replacement of my intake gasket(s) on a 99 Suburban K1500, 5.7l with 132k miles.
    First, I had coolant leaking at the intake manifold. The coolant was leaking into the oil, but the oil was not milky in the pan, though it was nasty in the valve covers and a little in the lifter valley. The truck was running fine other than the coolant leak.
    So... I tore it down and replaced the gaskets. Had to replace the EGR tube because it refused to come off the intake. No big deal, right?
    I cleaned out the covers and places I could see the funkiness in the valley, though I was sure I missed some.
    I also did a quick adjust on the valves because they were rattling a bit from a while back when I had to replace lifters.
    Got the engine back together and it started right up. I got a can of GUNK engine flush to clean out the remainder of the nasty oil... I let it run for a bit, drained the oil, replaced the oil and filter. Started the truck up again and let it heat up to operating temp and all seemed fine until the check engine light came on... was an O2 sensor heater circuit error (was getting this before the work too). Again seemed unrelated, just trying to get all the info.
    So the next day it snowed and I needed to take the Boy Scouts somewhere, so I took the truck. All appeared fine until I got off the highway and stopped at a light... the "check gauges" light came on and I saw the oil pressure was really low and dropped to zero. It came up if I tapped the gas. As soon as the light changed, I turned and pulled over. Checked the oil and the level was fine. I was only a little over a mile from the destination, with no other traffic lights... since the pressure was just below 40 as long as I was not at idle, I went the rest of the way. It was still running fine.
    We went to leave and the pressure was back to normal... As the engine heated, the pressure went back down. I figured maybe there was some residual engine flush thinning out the oil, so I went home.
    This morning, I got a new oil filter and more oil. Changed everything again and it seemed better.
    This afternoon I went to go out for dinner and all seemed fine, but it just didn't sound right. Shifts were too high and there seemed to be less power. I got about 2 miles from the house and stopped at a light and the engine just STOPPED. I pushed it off to the side when it acted like the battery was dead. I had someone come and give me a jump start and got it running, but now the engine really sounded like hell (rattling, kinda knocking, but not like a rod knock... little power and high shift points). Oil pressure was non-existant at idle, but came up near 40psi off-idle.
    I got it home and stopped in front of the garage and it just died when I stopped.
    Does it sound like something I might have done incorrectly, or just coincidence that maybe the oil pump failed... or the flush damaged something? I did notice that the volt guage showed lower than normal on the trip home as well.
    Just wondering if anyone has any clue where to look...?
    I really need this truck fixed and can't afford to drop it off with a mechanic (they wanted $600 for the intake gasket, which is why I did it myself in 10 degree weather).

  2. #2

    Default

    I hope I'm way off base and totally wrong here but it sounds like you might have eaten a bearing, could have been from the flush and previous work but really at this point that doesn't matter.
    With internal clanging and banging as you described it sounds like one of the main journal bearings might have been seizing, extra battery power helped the starter overcome the seized bearing and get it running again.
    Unfortunately none of this can be verified without some labor.
    Probably step 1 would be pulling the plugs and loosening the belts and seeing if the engine turns by hand, if it doesnt then you'll have to pull it apart.
    And even if it does turn by hand and you assemble it and start it if it has noise you still need to tear it apart.

  3. #3
    Jr. Apprentice
    Join Date
    Feb 2010
    Location
    Stroudsburg, PA
    Posts
    13

    Default

    Yeah, that's my fear. I've never been a fan of engine flush, but couldn't think of any other way to clean out the mess.
    Not sure though... I've had a spun bearing and this really doesn't sound like a rod knock or bottom end bearing. My dad suggested pulling a valve cover and checking the amount of lubrication... seems like an easy start. i am wondering if I jammed something installing the distributor... Been trying to think about it, but really coming up blank on logical explanations. At 132k miles, I am tempted to pull the motor and do a full rebuild... but not on my "best" 4x4 in January!
    How tough is it to get the oil pan off this thing? Is there clearance to remove it without dropping suspension or raising the motor?

  4. #4

    Default

    try some thicker oil like deisel oil and see if that will help your oil pressure. its cheaper then trying new bearings.

    you have hydrolic lifters in that engine right? i THOUGHT (but i dont know) that they required no adjustment. is it possibly to adjust them to the point where it will effect oil pressure?
    "i dont think you got the picture. i got a beautiful picture. this baby happens to have an extra turn of speed, which is the only thing i care about. you dont understnad what happens do you? they make cars. they make 'em exactly the same way. one or two of 'em turn out to be something special. nobody knows why. i know why. i may be kiddin' myself, but i think i can make somethin' out of that sad little bucket of bolts." ~ Tennessee Steinmetz

  5. #5
    Jr. Apprentice
    Join Date
    Feb 2010
    Location
    Stroudsburg, PA
    Posts
    13

    Default

    They are hydraulic rollers... They require a base adjustment and then re-check after "x" miles... I've been having valve chatter on startup for a while, almost implying that the new lifters were leaking down more than they should... but I attributed that to my lack of re-adjustment.
    I guess I really won't know much until I start looking inside.
    As far as oil, I went from the 5-30 that they originally gave me that the auto parts store to regular 10-40 on the second oil change, but really made little difference. If there's a problem, I hate to mask it with heavier oil unless I really think it'll get me through the winter and I can do a rebuild in the spring.
    Bob Hatton
    Stroudsburg, PA
    1999 Suburban K1500, 1992 GMC Jimmy
    1991 Suburban C2500, 1973 Chevy Blazer K15

  6. #6

    Default

    it was worth the shot.

    to the person who gave me negative Rep for being ASE certified and not knowing about the lifters:

    yes im ASE certified but i dont normaly do engine work. i ASSUMED it had hydrolic lifters but i dont like assuming openenly on the forums. id rather just admit im not sure.
    "i dont think you got the picture. i got a beautiful picture. this baby happens to have an extra turn of speed, which is the only thing i care about. you dont understnad what happens do you? they make cars. they make 'em exactly the same way. one or two of 'em turn out to be something special. nobody knows why. i know why. i may be kiddin' myself, but i think i can make somethin' out of that sad little bucket of bolts." ~ Tennessee Steinmetz

  7. #7

    Default

    Check for oil pressure at the filter. Oil passes through the filter before getting up to the heads and such. Make sure that's not plugged. Remove it and see if u pump oil out from there.

  8. #8
    Jr. Apprentice
    Join Date
    Feb 2010
    Location
    Stroudsburg, PA
    Posts
    13

    Default

    Have not done that, but I have replaced the filter 2x since the original intake gasket. My minor understanding of the oiling system is that it goes from the pan, through the pump, through the filter, then to the pressure sending unit, then is distributed to a series of passages I don't understand.
    Since I was getting pressure at the gauge and oil IS pumping up and pushing past the distributor housing, that the clog (if there is one) is past the filter and sender passages.
    Where does it go past the distributor? I've seen several diagrams, but none show the routing around the distributor. If I pull some lifters, should I see oil pumping there? Obviously I am not going to see it pumping at the crank since I am hoping to NOT get to the bottom end.
    Of course, if all else fails, pull the motor and full rebuild... hoping to avoid that if at all possible!
    Bob Hatton
    Stroudsburg, PA
    1999 Suburban K1500, 1992 GMC Jimmy
    1991 Suburban C2500, 1973 Chevy Blazer K15

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