Oil pump, or something else?????????

Discussion in '40- & 55-Series Tech' started by KliersLC, Nov 16, 2005.

  1. KliersLC

    KliersLC

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    Well, the 350 in the pig is running great, but I have noticed over the past few weeks that the oil pressure has been getting lower and lower, until now it sits at 0 at idle. It previously sat around 25 PSI at idle. It still comes up when driving, and it also has great pressure when it is cold. Otherwise truck runs great and has good compression.
    One last thing, if I let it idle for a while, a distinct tick can be heard from the top end. I was thinking it might be a lifter rattling because of lack of oil pressure, but since I am chevy stupid I don't know. It never made a noise before the pressure started dropping.

    I am suspecting the Oil pump, and have ordered a new High pressure pump(I hope I don't start blowing seals)

    Does anyone else have any other ideas of things that would cause this?

    thanks,
    Dan
     
  2. fng55

    fng55

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    test your gauge! esp. if it is electronic.
    change the oil?
    do you have any noise, like rod/ big end knock?
    check the rear main seal for leaks?
    i think there is an oil gally plug inside the timming cover, if this came loose you couild have presure loss w/out any external leak.
    if it's not the guage and the oil is good, the pump is the next easy thing to deal with.
    good luck, carl
     
  3. KliersLC

    KliersLC

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    Mechanical guage, known to be good, oil is Delo 15w40 with about 300 miles on it. No rod knock, but when the pressure is low and the engine is warm there is a soft bell like ringing coming from the bottom end toward the front. I was thinking that it may be the oil pump making that sound. Rear main is good. What is this oil galley plug?? is it accessed only by removing timing chain cover?

    Thanks for the suggestions, I may look into the oil plug that you mentioned.

    Dan
     
  4. Poser

    Poser Oh...Durka Durka Durka. s-Moderator Supporting Vendor

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    how many miles are KNOWN to be on the engine?
     
  5. KliersLC

    KliersLC

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    He he he ...........

    I was hoping no one would ask.

    I KNOW that there are at least 2k on it that I have driven. Swap was done in 2001 according to the SOR receipt. It is unkown if the engine was rebuilt, new, or a nasty dog turd at that point. Like I said though, it runs great and has good compression so I am hoping that this is something simple:D

    Dan
     
  6. azlar

    azlar

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    Sounds like a rod bearing going south. You've got advice on guages, now stick a scewdriver on the block with your ear to the end and listen. Or you can get a cheap sethoscope from HF or another souce and stick the rod in the noise location.

    It's amazing what a little sound/location can tell you.
     
  7. Mark W

    Mark W

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    Oil pumps really don't wear out nd cause low pressure. Bearings do. Your symtoms are classic for worn or even failed bearings,

    There is no oil galley plug under the timing cover. THe plugs for the main galley, at the front and back of the block almost never leak. The press in plug on the side of the head is the usual leakage point. When you do have a plug leaking it will not be enough to cause pressure loss. Unless it is also enough to cause siezed bearings and a catastrophic failure very quickly. In fact the one on the head will not cause pressure drop until all the oil has pumped out of the engine onto the ground. :(


    Mark...
     
  8. KliersLC

    KliersLC

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    Well, thats not what I wanted to hear, but I guess I may as well fix it right rather than throw money at it. I will try to locate the sound with a wooden dowell and see what that can tell me, but it looks like a full rebuild is coming soon. Bummer.

    thanks for the help,
    Dan
     
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