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Thread: Oil Pump Bypass??

  1. #1
    Join Date
    Oct 2003
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    Oil Pump Bypass??

    Anyone know if the oil pump in our Mod Motors has a bypass like old timers do??

    If so, what is the "Bypass Pressure" set at??
    No Marauder

  2. #2
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    The reason I asked this question is my oil pressure has been sliding lately....I think??

    The real OP gauge was one of my first mods and as I recall cold starts ran up to 90+ PSI and hot idle was around 20 PSI with hot pressure at 3000 RPM's about 50-55 PSI!! After the remote filter setup I think it dropped about 5 PSI??

    Well, lately it has run 10 PSI less across the board so I just figured with the engine getting up there in age the clearances are getting wider causing pressure loss!!

    I decided to try a new AutoMeter sender and WOW.....LIKE NEW!!! With 5W20 oil the cold (73*F) pressure is 85-90 PSI (was about 60 PSI with the old sender) and the other figures are falling in the original ranges!!

    So, I guess a sender can get lazy in time....over 4 years and over 150K miles??

    Just thought I'd post this in case anyone is seeing a drop in OP with an AutoMeter gauge!!
    No Marauder

  3. #3
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    Mines still going strong at 4+ years.

    P.S. Why don't you join us in Wilmington this weekend?
    Last edited by fastblackmerc; 10-12-2009 at 06:02 AM.
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  4. #4
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    I notice the needle becoming a little lazy but its showing true pressure.

    2003
    MERCURY MARAUDER 300A

    Build Date
    5/31/02
    Sequence#
    #363 of 7839 Black Marauders
    Dyno tested power
    450 RWHP & 405 RWTQ on 93 octane
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  5. #5
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    I've been thru about 5-6 senders for mine.
    Thanks to Darrin @ BC Automotive:
    $1800 and it was worse than when he started!

    Brian (FordNut) FPG # 1458 of 7838
    03 MM 300A (Lotsa mods, 130k mi) was 303rwhp/318rwtq N/A
    then 476/410 D1SC ProCharged on stock block
    then 660/555 D1SC PC on 5.3 wet sleeved Teksid alum big bore stroker
    then 365/369 N/A on 5.3 wet sleeved Teksid alum big bore stroker
    Now 751/617 3.4L Whipple on 5.3 Boss5.0 iron big bore stroker

    03 MM 300B Silver (Mostly stock, originally wife's car, 370k mi) FPG # 7053 of 7838 or 49 of 417 SB
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  6. #6
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    East Lansing, MI
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    same thing happened on my old sender for about 2 years then it died. Now with the new one it shows higher pressure


    11.90 @ 117.5mph on 93 octane
    324 shortblock, Novi 2000, Now with optional axle removing tires
    Igziabeher

  7. #7
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    I think that the Autometer sending units aren't sealed as well as they could be for all season, daily driver use. Other Marauder and Mustang owners have had this problem. Mine has been going strong for about 2 years now, but I won't be surprised when I have to replace the sending unit.
    -Matt

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  8. #8
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    Quote Originally Posted by FordNut View Post
    I've been thru about 5-6 senders for mine.
    I knew you had been through a bunch of them so I decided to spring for the $30.00 or so plus shipping and it paid off.....for a change!!
    No Marauder

  9. #9
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    Quote Originally Posted by illwood View Post
    I think that the Autometer sending units aren't sealed as well as they could be for all season, daily driver use. Other Marauder and Mustang owners have had this problem. Mine has been going strong for about 2 years now, but I won't be surprised when I have to replace the sending unit.

    I think your right. The way they built things now a days, its as cheap as possible. The sending unit is located down where water (with salt, road grime, etc) sprays right at it. It seeps into it over time, and corrodes the internals.
    Maybe, when new, seal any joints with a coating of silicone rubber or paint.
    2003 Blk CDN Marauder

    #5633 of build of 7838

    bone stock for now

  10. #10
    Join Date
    Sep 2008
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    USA
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    I run a mechanical oil pressure gauge, ran it for like 100K miles with zero issues. But I believe you are asking about the bypass spring pressure, not the oil pressure, correct?

  11. #11
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    Quote Originally Posted by massacre View Post
    I run a mechanical oil pressure gauge, ran it for like 100K miles with zero issues. But I believe you are asking about the bypass spring pressure, not the oil pressure, correct?
    Yep.....originally I thought with all the miles I have that PERHAPS the bypass spring had lost some tension letting the bypass open at a much lower pressure but it was the sender!!

    I'm gonna dissect the old one and see what makes it tick!!
    No Marauder

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