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  1. #1
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    1969 Fathom Green Coupe

    Default Oil Pressure Gauge Question

    I am a new member to your site and need help with 1969 C3 oil gauge.
    Your site is very informative and well done so my question is:
    Can air get trapped in oil line that go to cabin oil pressure gauge if
    so can that be giving me the fluctuating readings on gauge and how
    do I bleed it out? Thanks Rusteze,

  2. #2
    Moderator bill81vette's Avatar
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    Default

    I believe the gauge is electronic
    Perhaps your sending unit is going bad..

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  3. #3
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    Member Vettehead Mikey's Avatar
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    The stock gauge on a '69 is mechanical. It doesn't matter whether air is trapped in the line or not- pressure is pressure. Air might actually help dampen any fluctuations.

    When do you get these fluctuations and how large are they?

  4. #4
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    Default

    Thanks Bill81Vette, Glad I found you guys, need to do better research in my Service Manual. Rusteze

  5. #5
    Member TimAT's Avatar
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    69 gauge is mechanical. Having air in the line is no deal at all. If you're seeing big jumps in the reading one possibility is the bypass at the oil filter mount is having a problem. Opening and then closing.
    If anyone has extra horsepower not doing anything, I can always use more.

  6. #6
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    1969 Fathom Green Coupe

    Default Oil Pressure

    Thanks Guys, would never of found these kinds of solutions in the manual will look in to all of them. Rusteze

  7. #7
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    1969 Fathom Green Coupe

    Default Oil by-pass

    Thanks for all the input guys, Looks like there is no sending unit on this one, there is however a fitting just above the spin on filter a 1/16th tube [ a Bourdon] as it called goes directly to the gauge. The first time I start it 35 to 40 psi then after it warms up it starts. So TimAT can you tell me more about the oil by-pass or any one this looks like the issue. Rusteze

  8. #8
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    Member Vettehead Mikey's Avatar
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    Quote Originally Posted by rusteze View Post
    The first time I start it 35 to 40 psi then after it warms up it starts.
    35-40 psi on a cold engine sounds low to me and marginal on a hot engine. When you say 'after it warms up it starts' what's 'it'?

  9. #9
    Member TimAT's Avatar
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    Quote Originally Posted by rusteze View Post
    Thanks for all the input guys, Looks like there is no sending unit on this one, there is however a fitting just above the spin on filter a 1/16th tube [ a Bourdon] as it called goes directly to the gauge. The first time I start it 35 to 40 psi then after it warms up it starts. So TimAT can you tell me more about the oil by-pass or any one this looks like the issue. Rusteze
    Correct- that little tube above the filter goes to the gauge. Technically speaking, the "Bourdon" tube is internal to the gauge. You might take a close look at that tube- from the engine all the way to the gauge. If it's got a spot that's starting to seep or even if it shows a little sign of rubbing on something a failure might be in the near future.
    The oil filter bypass is attached to the block- the oil filter mounts on it.
    I might think about installing a temporary gauge and seeing if it follows the factory gauge.

    The way I read the above, the gauge reads steady until after the engine and oil warm up, and then starts fluctuating. IS that correct?
    Last edited by TimAT; 04-16-13 at 06:18 PM.
    If anyone has extra horsepower not doing anything, I can always use more.

  10. #10
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    1969 Fathom Green Coupe

    Default "Whats It"

    Sorry, After warm up or running a while the gauge [oil]reads like the tachometer drops down below to 25psi at 2000rpm and up to 50psi+ when past 3500rpm then holds.What is the safe operating reading if the gauge is working properly? Rusteze

  11. #11
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    Member Vettehead Mikey's Avatar
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    Quote Originally Posted by rusteze View Post
    Sorry, After warm up or running a while the gauge [oil]reads like the tachometer drops down below to 25psi at 2000rpm and up to 50psi+ when past 3500rpm then holds.What is the safe operating reading if the gauge is working properly? Rusteze
    That sounds perfectly normal to me. Oil pressure rises with engine speed, up to the point where the pressure relief valve opens.

  12. #12
    Member TimAT's Avatar
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    I agree with Mikey-- I don't see a problem.

    Cold, I get nearly 80 PSI- once it gets hot, it runs around 65 PSI. With the oil pump I have, that's about right on for my engine. (it's NOT stock).
    If anyone has extra horsepower not doing anything, I can always use more.

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