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No Oil Pressure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by **DONOTDELETE**, Apr 24, 2000.

    Just recently I noticed that My Oil Pressure, which is low to begin with, drops all the way to 0 whenever the truck is not moving. The funny thing is that the pressure will stay around 30 when the truck is moving, even if I'm not pressing the gas. Is this the oil pump? I checked, and my oil level is fine so what could this be and how might I go about figuring out what this is? Please get back to me. Thanks Guys,


    <font color=red>ABO</font color=red>
     
  1. jmpd

    jmpd 1/2 ton status

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    Is it possible that the sending unit is going bad? Or just a badge gauge?
     
  2. Mudzer

    Mudzer 1/2 ton status Author

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    Your oil pressure should go up as the RPM's increase. How many miles do you have on this motor? Mine has 165xxx and it is starting to show signs of wear. I recently installed a high volume oil pump that got me a few more miles out of mine. Usually if the rod bearings are getting loose, you will hear a knock. When Main bearings get loose, sometimes you may not hear a knock. One sure fire hint of bad Main bearings, is - Under a load, when you increase the RPMs, the Oil Pressure Drops. Cam Bearings also could have alot to do with your oil pressure woes. Of course, I would check the motor with a good mechanical gauge. If your motor is dropping lower than 5 pounds, chances are you have some problems or will soon. My 400 carries 30 psi at idle in neutral, hot. When I pull it into gear, it goes down to 20 psi. I have Autometer gauges and a 15 psi sending unit on an Autometer Pro Light. You may try a couple of things after testing the pressure with a mechanical gauge. Switch to a semi synthetic oil. This helped my motor alot. You can also pull the pan and install a high volume pump. This will only provide more oil, not fix your bearing problem. Be sure to install a new rear main seal while you have the pan off, if yours is leaking. I also pulled the rear main cap off and inspected the bearing. Mine looked pretty good for the amount of miles. Good Luck.

    <font color=red>Mudzer</font color=red>
    1978/91 K5 Blazer
     
  3. Oil Man

    Oil Man Registered Member

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    No oil pressure can come from a few different things, If your oil pump is worn out, if your bearings have too much clearance, If the oil pump is loose from the block sucking air at low rpm's, Is your oil fresh? or does it have a lot of miles on it? Did this happen after you changed oil or has it been getting worse over time? I think we need more info to help you figure out the problem but these things might give you a start.

    Sincerely, Kevin
     

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