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Thread: Low Oil Pressure at Idle

  1. #1
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    Default Low Oil Pressure at Idle

    Only put about 100 miles on the car and wondering whether these issues seem normal.

    I just fixed the A/C compressor lines (so A/C works now), and when turning on the compressor it drops idle-speed by about 200 rpm.

    Before the fix, the idle was right around 1000 rpm as Josh previously tuned. With the new lower idle in these conditions:

    (1) Ambient Air Temperature is 105-110 degrees
    (2) A/C turned on
    (3) Idle is at 800 rpm with the compressor on (1000 rpm otherwise)
    (4) The vehicle is fully warmed up (cold pressures are higher)

    The oil pressure light flickers on and off. I've heard the warning threshold is 15psi, and simultaneously that warm idle can be from 10-15psi. The oil level itself is fine - any ideas what could be the cause? No abnormal noises or other effects, but I won't drive it until I can diagnose more.

  2. #2
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    Depends on what oil squirters are fitted, if the standard brass jet type then typically oil pressure on idle when hot is low. Best to fit an oil pressure gauge so you can see what your pressure is what ever.

  3. #3
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    The US AER engines do not have brass squirters. NobleM400 did a nice job rectifying this.

    http://www.nobleforums.com/showthrea...&highlight=oil

    http://www.nobleforums.com/showthrea...ght=oil+squirt

  4. #4
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    Im going to swap oil first, then measure and log pressures throughout the RPM range. I'had been fidgeting with the A/C lines and had no issues beforehand, so hopefully this is bad ground issue rather than real pressure drop (<4psi). The light doesn't stay on but has a flickering that's worrisome.

    Fingers crossed its nothing worrisome.

  5. #5
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    Never had an AER engine apart but unless I read it incorrectly they still have oil squirters so whether they are drilled holes or brass jets is irrelevant, they have holes that pass oil all the time. The mountune / Roush built engines used a valve type which closed at below 2bar so overcame the problem, however due to the size of them the block is prone to cracking.

  6. #6
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    Can anyone give me an approximate range of pressures to expect across the rev-range. Normally I've heard 10psi per 1000 rpm's as a rough rule of thumb.

    Additionally, I've bought a more professional test-kit to give more accurate low pressure readings than the M400 gauge. What are the easiest pickup ports? Worst case was going to use the low-pressure warning pickup point itself.

    Really hope this is a sensor issue considering I just bought the car and have barely 100+ miles while chasing other demons...

    - Chris

  7. #7
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    When engine is warm, my M400 oil pressure gage reads 15-ish at idle (gage isn't very precise at that level as you pointed out), but picks up into the 40-60 psi range at higher rpm. When oil is cold, it's 40 psi at idle. I use 5W40 Redline.
    2007 M400, NUS 206

  8. #8
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    Quote Originally Posted by Bill View Post
    When engine is warm, my M400 oil pressure gage reads 15-ish at idle (gage isn't very precise at that level as you pointed out), but picks up into the 40-60 psi range at higher rpm. When oil is cold, it's 40 psi at idle. I use 5W40 Redline.
    I run 5W40 too and this is pretty much what I see with my car also

  9. #9
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    Quote Originally Posted by doug_porsche View Post
    I run 5W40 too and this is pretty much what I see with my car also
    I'm seeing:

    (1) 10-12 psi at idle
    (2) 35-40 psi at 2500-3000 rpm
    (3) 50-60 psi at WOT

    The gauge does fluctuate a bit (+/-3 psi under load at higher rpm). Conditions for reference:

    - 105 Ambient Temperature
    - 5W40 oil (haven't switched to thicker yet)
    - Pressure is measured at the outlet of the old sensor
    - Gauge is an industrial large-diameter line (fewer issues at low pressure).

    Seems to be slightly low at idle, but okay at operating temperatures.

    - Chris

  10. #10
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    You are way over complicating this
    is it a full synthetic

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