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Thread: Oil temp measuring

  1. #1
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    Oil temp measuring

    I've been debating this idea for awhile. I *think* the oil drain plug threads on the "early" Chev small blocks (before they went metric apparently) might be compatible with the Chevy coolant temperature sensors used for the coolant temp gauge, in the drivers side head. Two thread sizes, early was large, later was small, but I believe later is 3/8" NPT. I can't find anything stating what the stock oil pan threads are though. 3/8" sounds about right for mine. Two good things there...my oil pan drain plug comes off nearly parallel with the ground, so very little risk of snagging it on something, and the later coolant temp sensors had pre-attached wiring, which would be more resistant to coming off. With the oil pan being so close to the front axle on 4WD, I think there is little risk of hitting it with anything.

    Thus, I think it would be possible (and relatively easy) to use a stock coolant temp sensor to monitor engine oil temps. My reasoning of course is because of how hard on oil highway mode can be.

    I have the engine oil cooler setup on my K5, so I'm not that concerned with temperature, but it would be a nifty gadget, and would be interesting to see how much of a difference there is between highway and non-highway mode oil temps. Eventually I'd like to compare oil temps with and without the cooler itself (regardless of highway mode) to see how effective it is.

    I wonder if there is any location within the ECM that would allow an ECM coolant sensor to be used for oil temp, essentially two temperature inputs that could be datalogged? I suppose the stock ECM coolant temp sensor could be used, but I have to assume oil temps get too high, and would cause some bad running.

    If that is possible, it would then be possible and very easy to wire up a stock truck coolant temp gauge to monitor that sender, or any gauge that operates the same way.

  2. #2
    RIP EagleMark's Avatar
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    As far as going to gauge that would be up to gauge, actually just wire it into coolant temp gauge would work. Putting it in data stream code be done, there are spots in bin to change ALDL output to another item, where to put it in ECM? What ECM?

    I could add an item to ADX file or change one that's there. I have an AutoProm so I could use one of the three inputs for this during dataLog. Have to have an open slot in ECM though like if there were no EGR! Or?

    In the end we could watch oil temp and have a real life test for oil temp increase. Other benefit would be able to watch oil temps for advancing timing! So cool idea!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  3. #3
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    Stock oil pan drain plug threads were 1/2-20 straight (bolt) thread on all SBC and BBC until the "Metric" revolution (then they were 12mmX1.75) . You are correct about the later temp sensors being 3/8" NPT , the early sensors were 1/2" NPT .

    If you use an aftermarket sensor with an 1/8 NPT thread , B&M makes a drain plug kit (http://www.summitracing.com/parts/BMM-80250/) that will screw into the early 1/2-20 oil pans and let you screw in a 1/8 NPT sensor , it is how I monitor Oil temp on most everything I drive with an aftermarket gauge , as far as using one of the aftermarket sensors and inputing that reading into the ECM/PCM , hopefully someone with more knowledge will chime in on that .

    FWIW , if somebody (smarter than me) had this input avalible in $OD and/or $OE using a specified sensor , I would be all in to get this in the datastream. I have some aftermarket (1/8"NPT) Autometer sensors I could measure resistance if need be .

    TOM
    Last edited by Nasty-Z; 03-13-2012 at 10:35 PM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
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  4. #4
    RIP EagleMark's Avatar
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    Not sure what aftermarket sensors read? But CTS values of GM units is known and lookup tables are already done in ADX files, so that is cheap piece with known values.

    Coolant Tempreture Sensor readings Link

    EDIT: Temp sensor readings can be changed in ADX lookup table.

    Coolant sensor approximate resistance specifications:
    Code:
    177 ohms @ 212 deg. F. or 100 deg. C.
    241 ohms @ 194 deg. F. or 90 deg. C.
    332 ohms @ 176 deg. F. or 80 deg. C.
    467 ohms @ 158 deg. F. or 70 deg. C.
    667 ohms @ 140 deg. F. or 60 deg. C.
    973 ohms @ 122 deg. F. or 50 deg. C.
    1188 ohms @ 113 deg. F. or45 deg. C.
    1459 ohms @ 104 deg. F. or 40 deg. C.
    1802 ohms @ 95 deg. F. or 35 deg. C.
    2238 ohms @ 86 deg. F. or 30 deg. C.
    2796 ohms @ 77 deg. F. or 25 deg. C.
    3520 ohms @ 68 deg. F. or 20 deg. C.
    4450 ohms @ 59 deg. F. or 15 deg. C.
    5670 ohms @ 50 deg. F. or 10 deg. C.
    7280 ohms @ 41 deg. F. or 5 deg. C.
    9420 ohms @ 32 deg. F. or 0 deg. C.
    12300 ohms @ 23 deg. F. or -5 deg. C.
    16180 ohms @ 14 deg. F. or -10 deg. C.
    21450 ohms @ 5 deg. F. or -15 deg. C.
    28680 ohms @ -4 deg. F. or -20 deg. C.
    52700 ohms @ -22 deg. F. or -30 deg. C.
    100700 ohms @ -40 deg. F. or - 40 deg. C.
    
    ADX lookup Table
      <ADXLOOKUPTABLE id="10" idhash="0xDE6A9050" title="Coolant Temp in C">
        <desc>&lt;Comments&gt;</desc>
        <inputtype>1</inputtype>
        <outputtype>3</outputtype>
        <lookupmode>0</lookupmode>
        <entrycount>39</entrycount>
        <tableentry input="1.000000" output="200.000000" />
        <tableentry input="13.000000" output="150.000000" />
        <tableentry input="14.000000" output="145.000000" />
        <tableentry input="15.000000" output="140.000000" />
        <tableentry input="17.000000" output="135.000000" />
        <tableentry input="19.000000" output="130.000000" />
        <tableentry input="22.000000" output="125.000000" />
        <tableentry input="24.000000" output="120.000000" />
        <tableentry input="27.000000" output="115.000000" />
        <tableentry input="31.000000" output="110.000000" />
        <tableentry input="35.000000" output="105.000000" />
        <tableentry input="40.000000" output="100.000000" />
        <tableentry input="45.000000" output="95.000000" />
        <tableentry input="51.000000" output="90.000000" />
        <tableentry input="57.000000" output="85.000000" />
        <tableentry input="65.000000" output="80.000000" />
        <tableentry input="73.000000" output="75.000000" />
        <tableentry input="82.000000" output="70.000000" />
        <tableentry input="93.000000" output="65.000000" />
        <tableentry input="103.000000" output="60.000000" />
        <tableentry input="115.000000" output="55.000000" />
        <tableentry input="127.000000" output="50.000000" />
        <tableentry input="140.000000" output="45.000000" />
        <tableentry input="153.000000" output="40.000000" />
        <tableentry input="166.000000" output="35.000000" />
        <tableentry input="178.000000" output="30.000000" />
        <tableentry input="190.000000" output="25.000000" />
        <tableentry input="200.000000" output="20.000000" />
        <tableentry input="210.000000" output="15.000000" />
        <tableentry input="219.000000" output="10.000000" />
        <tableentry input="226.000000" output="5.000000" />
        <tableentry input="232.000000" output="0.000000" />
        <tableentry input="238.000000" output="-5.000000" />
        <tableentry input="242.000000" output="-10.000000" />
        <tableentry input="246.000000" output="-15.000000" />
        <tableentry input="248.000000" output="-20.000000" />
        <tableentry input="251.000000" output="-25.000000" />
        <tableentry input="252.000000" output="-30.000000" />
        <tableentry input="256.000000" output="-40.000000" />
      </ADXLOOKUPTABLE>

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  5. #5
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    So the pan is not NPT, but the senders are, thus won't work as-is.

    I know there is a bushing for using the 3/8" sender in a 1/2" head, anyone aware if there is a bushing 3/8 NPT to 1/2" normal thread? Not finding anything via Google. Have a buddy who does some plumbing, if he's got the right size pipe tap, could certainly make the right piece, as there are 1/2" to 1/4" (or 1/8") bushings. He might be interested in this idea as well. :)

    Only reason I thought of the stock sender is that I have a fair number of them around. I'd prefer to decrease my piles of parts lol.

    Edit: Is there any way the gauge sender could be used by the ECM, as opposed to the coolant sensor? I understand the difference between the two (CTS using reference voltage) but is there some way the ECM could simply measure resistance to ground, just like the gauges do?

    Certainly nice to add the info to the datastream, a gauge is the more low-tech method. In the datastream I assume you could say "it went Hiway mode here, and oil temps started to climb at the same time", or similar. Versus staring at the laptop screen and another gauge.
    Last edited by dyeager535; 03-13-2012 at 11:04 PM.

  6. #6
    RIP EagleMark's Avatar
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    Nasty Z gave a link to adapter that would work, it is designed to be added to trans pan but has right specs to go in your oil drain hole.
    http://www.summitracing.com/parts/BMM-80250/?rtype=10

    Might be a cheaper brass fitting available?

    Using stock CTS sensor is easy start, cheap part even if new. Not sure if it would work tied to ECM and a gauge... Probably not as the stock EFI system has seperate sender for gauge and ECM.

    Not sure on rest..

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  7. #7
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    Darn, looks like lost post. Stupid work. :)

    Brass and steel 1/2-20 to 1/4 or 1/8 bushings are available. Would just need to tap it to 3/8 NPT. Should be simple. FINDING a bushing locally that fits the bill might be a bit more challenging, but they are available online.

  8. #8
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    later coolant temp sensors were 3 wire, 2 for the ECM's A/D circuit, the last for driving the gauge. seems like an easy and thorough way of doing it.

    also, IIRC, the 90-91 corvettes w/5.7 TPI used an oil temp sensor from the factory. that's on a 1227727, but still, any ECM that has at least 1 spare 5V biased A/D channel will work. just need to change the normalization conversion depending on the resistor that's feeding the sensor.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  9. #9
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    Do you know what year/application they started using the three wire coolant temp sensors? I have wondered for quite some time why they went to three wire oil pressure senders/switches but kept the separate CTS/gauge sender for coolant. Apparently they did at some point. I hadn't run across a three wire coolant device, or I would have swapped mine already!

    Another possible "feature" would be if it were possible to trigger a "check engine" light with a low or high temperature reading...could use the temp sender as a low oil/hot oil warning as well, if it were placed in the pan in a location that was normally well immersed in oil with the engine running.

  10. #10
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    10096181

    that's the part number for the one i'm thinking of. check it out on rockauto, you'll get a good idea of what they were used in.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  11. #11
    RIP EagleMark's Avatar
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    Cool! I got one of those brand new in box sitting here, came in a bunch of stuff I got of eBay! Sweet, will do ECM and a gauge... wonder if it will run an aftermarket gauge? Just looked at RockAuto and they are cheap as well.

    1/4 inch hole should tap easy to 3/8 NPT!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  12. #12
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    ?s. PCM? MASK? Trans? Reason I ask is, if '7427 w/Manual, there would be an unused temp input for trans fluid temp.

    AutoMeter has some 1/8"NPT temp senders, I have one in intake and one in radiator.

    http://www.summitracing.com/parts/ATM-2385
    Last edited by gregs78cam; 03-14-2012 at 04:23 AM.
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  13. #13
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    Quote Originally Posted by EagleMark View Post
    1/4 inch hole should tap easy to 3/8 NPT!
    A 1/4" hole will not tap to 3/8"NPT .

    3/8" NPT requires a 9/16" (.5625) hole to start with .

    Only problem I see with using a stock sensor is that even the small 3/8" NPT would require you to remove the pan to tap for a fitting that big , there is not enough meat on the nut on the inside of the pan to go much bigger . Although I would not want to tap it with it still installed anyway .

    TOM
    Last edited by Nasty-Z; 03-14-2012 at 04:04 AM.
    1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
    1992 S-10 434 SBC/Tremec - '7427
    1986 Monte Carlo SS
    1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
    1980 Z-28 496/700R4
    1979 Corvette 496/700R4
    1977 Olds 98 Regency 403/700R4

  14. #14
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    That's a bummer. It would have to be the B&M setup then for the pan plug. Of course, once you get to the point of buying a tap, or welding fittings on pans, whatever, it's probably the cost of just buying an aftermarket sender.

    Any chance GM (or anyone) went with smaller than 3/8" coolant stuff?

    IIRC, the oil pressure switch/sender that screwed into the block was 1/8" or 1/4" (MOST oil holes in the block were 1/8) finding a smaller stock sensor could be another option as well.

    One above the oil filter, if tapped, was typically 1/4"? I suppose you could "upsize" one of the block fittings, but not sure how accurate the oil temp would be compared to pan. Never have seen oil temp at various locations in the block covered.

    Still have the aftermarket sender option, but the three wire stock one is attractive.

  15. #15
    RIP EagleMark's Avatar
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    Don't know what ECM mask trans yet, think dyeager has a few, me too...

    I keep telling you guys I'm not good with math! Unless it's a wrench! Got my 8ths and 16th with 4th all mixed up...

    The three wire coolant sensor I have 5/8 inch in thread grooves. Is it metric 16mm? The small 2 wire I think is a gauge as the other one just mounted in kids truck was bigger, it is 7/16 or 11mm.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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