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Oil pressure question...need your expertise.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by heavy4x4, Dec 21, 2002.

  1. heavy4x4

    heavy4x4 1/2 ton status

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    Hey, all. Got an oil pressure question. Yes, I did a search...but none of the info was what I was looking for.

    Upon startup...my truck's oil pressure is around 40-45 and it will stay at that pressure at idle, no matter what the engine temperature is. So, that is obviously not my question/concern. Here it is: when driving/applying throttle, the gauge climbs to 60 and frequently goes over that mark. This happens not only at high rpm's (common for oil pressure to increase with rpms) but also when running at the low rpms my overdrive provides. When the guage is past 60, I don't notice any weird noises, smells, or any weird driving characteristics. Also, if parked, and I blip the throttle a small amount, but quickly, the gauge jumps up past 60 and then back down to normal, quickly. Anyways, to keep this short, here are my questions:
    1) Is high oil-pressure something to worry about?
    2) What, on a worn - 160,000 mile engine, could/would cause high oil pressure?
    3) Should I maybe replace the oil pressure sending unit? (I don't think that's the problem because it's never completely pegged, and it's a steady climb up and down from 40-60+ and vice-versa)
    4) Should I not worry about it...it's rather common/not going to hurt anything?

    Thanks for any input. /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
     
  2. TX Mudder

    TX Mudder 1/2 ton status

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    Pressure is a function of resistance. On a high mileage motor with worn clearances, one would expect lower pressure due to lower resistance.
    You either have a tight motor or a resitriction somewhere.
    That does sound unusually high for an older engine. I don't have any experience with an electric oil pressure gauge, so I can't help you there.
    -- Mike
     
  3. motorheadnelson

    motorheadnelson Registered Member

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    Has it always done this, or is it something new? If it has always been this way, it probably has a high volume pump with the 'purple' spring in it. I just pulled out my high mile smallblock, running about the same pressure. I use a mechanical gauge, don't like electric ones. Buy or borrow a mechanical gauge to double check your readings. Myself, I like the pressure, but a high volume pump offroad may need a little more oilpan to prevent starvation.
     
  4. heavy4x4

    heavy4x4 1/2 ton status

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    Thanks for the responses so far.

    Only after around 120,000 miles did the oil pressure start doing this. And it wasn't immediate...it gradually started showing higher and higher pressures. I thought restrictive passages too, so I did an oil cleaner/solvent thing during an oil change...that didn't do anything. Does that help you out at all? I'd be happy to answer more questions if need be. I just want to know if this is something to worry about. Is my engine going to blow if I run it past, what the gauge says, 60 psi?
    Also, a little added info...if it's over 60 on the freeway, and I hit the gas to go up an incline, the tranny will downshift, the engine rpm's will go up, and the oil pressure will go down a bit. Then, when rpm's go back down when it shifts into overdrive, the oil pressure will be back up past 60. So...this is what lead me to believe blocked/restricted oil passages...but like I said, the oil cleaner stuff I used didn't seem to help. I'm out of ideas.
     
  5. heavy4x4

    heavy4x4 1/2 ton status

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    ttt - does anyone know if I'm wrecking my engine by running it at, what the gauge says, over 60psi oil pressure???? /forums/images/graemlins/confused.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/ears.gif
     
  6. Muley

    Muley 1/2 ton status

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    Mine does that on my K5. I would personally change out the oil pressure sending unit. Should solve it. New sending unit is only about $20.00.
     
  7. Klink K5

    Klink K5 1/2 ton status

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    I'm wondering if the thrust bearings are going out on your crankshaft. Sounds like the same problem I had with a 305 once. When you smash on the gas pedal, oil pressure would fall, back at normal driving the oil pressure would be higher. The easiest way to check if the thrust is going out is to remove the trans inspection cover and grab the ring gear and see if you can move the crankshaft foward or backward. Easier than that, grab the crank pulley and try moving it that way. If you fell alot of slop or movement in the crank, this is probally where your oil pressure is falling and rising. I hope this helps! /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     
  8. Stormbringer

    Stormbringer Registered Member

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    Hi All!

    Nice site you have here.

    I'd change the sending unit. It's cheap and a fairly straightforward procedure. On my 87, (190k miles on the 305 )I showed no oil pressure at all when I got off the PA turnpike.. after the initial freakout, I realized that the engine wasn't making any ugly noises, and I did show some pressure under accelleration so I kept pushing it to my mother in laws house in pittsburgh..

    The auto parts guy said that a new sending unit cured similar behavior on his suburban, so I took his word for it, and the problem went away. My motto is replace the cheap stuff first.

    Tom /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  9. Sandman

    Sandman 3/4 ton status Author

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    I would suspect the electric sender. Sounds like the internal resistance is crawling up wich means dirty and bad.
     
  10. heavy4x4

    heavy4x4 1/2 ton status

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    Thanks everyone...I think I'll replace the sending unit soon, and let you know what happens.
     
  11. heavy4x4

    heavy4x4 1/2 ton status

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    Oh yeah...where is that sender again...on the back of the block near the distributor?? For some reason that spot rings a bell. I'd look in my Hayne's, but I don't have it at home with me.
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I don't trust electric gauges. All an electric gauge is telling you is that you have some oil pressure. I don't trust it to tell you how much or how little. Trust only a mechanical gauge to tell you that. I've got one mounted in my dash that costed a whole $7 at Wal-Mart.
     
  13. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Yeah behind the distributor on most for the gage. might be a couple of senders back there. one will be for the Computer. Might also be above the oil filter on the side of the block. Usualy about 1.5 inches in diamerter about 2 inches long or so fot the main body and then the threads will stick out one end. Quick test would be to un plug and fire it up and see what the gage does. If it just sits then you got the right one.
     
  14. Sandman

    Sandman 3/4 ton status Author

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    This can also be a pain in the a$$ to change that thing...
     
  15. heavy4x4

    heavy4x4 1/2 ton status

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    What makes it difficult to replace??? The location...or the actual removal process??? Does it have any sort of standard head on it that I can get a wrench on? I am kind of planning on doing this tomorrow...but we'll see. Also, where is a mechanical oil-pressure gauge plumbed in? I'm assuming a line brings pressurized oil all the way to the back of the gauge...so what does the line splice into? Thanks.
     
  16. Sandman

    Sandman 3/4 ton status Author

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    OK, It can be a pain because it looks like a very tall mushroom and the part the you get a wrench onto to unscrew it is on the bottom. In the way of your wrench is the distributer, firewall, valve covers, and about 300 wires and other things. This is the same spot that you would put a mechanical guage into. Its just a threaded hole in the top of the block right next to the base of the distributer. there might be an angled fitting as well that help to get it out. Once you get in there and take a look it shouldnt be to bad.
     
  17. heavy4x4

    heavy4x4 1/2 ton status

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    Thanks a bunch...I'll look at it tomorrow. Not sure if I'm going to replace it yet.
    My main goal tomorrow is to figure out (and fix) the leak coming from my AC compressor. /forums/images/graemlins/frown.gif /forums/images/graemlins/mad.gif
     
  18. zakk

    zakk 1/2 ton status

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    leaking AC doesn't gernade motors /forums/images/graemlins/grin.gif

    i had a chaffed wire that was causing semi-simular spiking, etc. (being that it was grounding out) Might want to make sure all the wiring is OK and in good repair.
     

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