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M20 Stroker "Budget" Build - Oil Pressure Issues Only at Idle

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    M20 Stroker "Budget" Build - Oil Pressure Issues Only at Idle

    Hey all,

    Had an M20 stroker engine built up from what I was told was a good condition S-ETA block (visible cross-hatches in the cylinder walls and all) and a freshly machined M20 i head. As it was a budget build, I'm not sure much of the mechanicals in the block were touched, if any, although I know the oil pan was re-sealed and the mating portion of the block cleaned.

    Received the car back with the engine in June, didn't have many issues, and (mostly) successfully drove the car from Colorado to Ohio and back. Overall, I've put roughly 4,000 miles on the rebuild.

    One of the things I had installed were a set of VDO gauges, two of which handle oil temp and oil pressure. They're mounted using a SSSquid Oil Sender Adapter (no longer sold on their website: https://sidonriver.com/e30-bmw) and up until this past Friday my oil pressure was roughly 50psi under normal load, somewhere around 65-80 on startup, and idled around 10-20psi when I would look. On Friday, I was driving about 15 miles out when I noticed rolling up to a stop light at idle that my oil pressure was LOW. Like, just above the 0psi hash on my 0-100psi gauge. The pressure responded normally otherwise, it would immediately bring the oil pressure up if I barely touched the throttle, and driving the pressure was right around the 45-55psi range. I went ahead and changed the oil (Mobil1 High Mileage 10w40) to see if that would have any effect, but after letting the car run for a bit and then driving it a short distance, idling brought the oil pressure down that low again.

    Some notes:

    -I don't think the oil pressure light on the cluster was wired to the new oil pressure sender in conjunction with the gauge. Bulb works, as it's new and lights up on start.
    -RPM's are currently wildly inaccurate, as the mechanic tried to code the RPMs based on "pulses" with MegaSquirt (I have the plug and play ECU).
    -Engine runs cool, oil temperature reads a bit over the 200 degree mark when driving around and the engine's had time to warm up.
    -My car has headers, which I've noticed heats the hood up a LOT and also they sit very close to the oil filter. I doubt that's causing oil to heat up enough to drop pressure though.

    The original engine in my car was an M42, and so this is a pretty new engine/setup to me and I want to make sure I don't immediately grenade this thing.

    So is this just a case of oil pump replacement, or are there other things I can check to see why this suddenly started occurring before I tear the bottom half of the engine off and swear a lot?

    Thanks for any input or advice.



    #2
    if the pressure has only changed at idle (i.e. same at all other conditions) then i suspect one of two things firstly
    - gauge is reading wrong
    - oil temps are much higher now

    So get a second opinion. do you have a mechanical or other gauge to check the pressure directly?

    FYI, you can get a VDO pressure sender with the built in pressure switch that provides a warning light on the dash as per stock but instead of 7psi it's like 8.5psi
    89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

    new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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      #3
      Originally posted by digger View Post
      if the pressure has only changed at idle (i.e. same at all other conditions) then i suspect one of two things firstly
      - gauge is reading wrong
      - oil temps are much higher now

      So get a second opinion. do you have a mechanical or other gauge to check the pressure directly?

      FYI, you can get a VDO pressure sender with the built in pressure switch that provides a warning light on the dash as per stock but instead of 7psi it's like 8.5psi
      Thanks for that! I did find about about the VDO sender with built in switch, once I solve this issue I'll be getting once of those and adding it in (I'll have to find that old wire for the light too).

      I don't have a mechanical gauge but I live walking distance from an Advance and I'm sure I could rent one. Just unscrew the VDO sender and install gauge there? Or is there a better spot?


      Comment


        #4
        Yeah screw into same location
        89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

        new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

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