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Thread: NA8 Compression check and Seafoam

  1. #1
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    Default NA8 Compression check and Seafoam

    So I started by taking out the plugs, getting pictures then putting the somewhat piss poor borescope down into the pistons to have a look before the first crank of the day.

    Cylinder 1:2017-12-31-14-17-58.jpgIMG_0054.jpg
    Cylinder 2:2017-12-31-14-21-41.jpgIMG_0055.jpg
    Cylinder 3:2017-12-31-14-24-56.jpgIMG_0056.jpg
    Cylinder 4:2017-12-31-14-27-19.jpgIMG_0057.jpg

    Put everything back together than ran up to the store to grab the foam and the compression tester. Grabbed the spray can foam that has a nozzle you can install in the intake. Finished off the can of Seafoam then took it up the road and drove the piss out of it for about 15 minutes. Came back and pulled the plugs back out to take another look at the piston tops after the seafoam.

    Cylinder 12017-12-31-15-20-19.jpg
    Sorry didnt get cylinder 2, forgot lol
    Cylinder 32017-12-31-15-32-38.jpg
    Cylinder 42017-12-31-15-32-19.jpg

    So it looks to have done something I suppose.

    Next were compression checks. Unplugged the fuel? relay under the dash and let the car die. These were performed dry with the engine still hot and starter pulsed twice for 3 seconds. Didn't open the throttle as I wasn't aware that it needed to be, but if it does then please someone chime in and say so. And it was a Bosch tester so I'm unsure if those are wildly inaccurate or not.
    1:163
    2:150
    3:150
    4:178
    Have pics of the gauge readings but I don't think anyone would care to see those.

    I'm trying to track down some heavy white smoke during early morning startups that disappears when warm. It doesn't puff on rapid accelerator release and some mornings it doesn't smoke at all so I'm confused. Seems like maybe the head gasket between 2 and 3 as those have the lowest numbers and 3 seemed to be the cleanest cylinder among the three I viewed.

    Thoughts? If I performed anything wrong please feel free to point it out!
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  2. #2
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    One more thing to add, no.3 started smoking after performing the compression test and pulling the tester out. Wth is that about? None of the other cylinders did that.
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  3. #3
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    Sorry if it's in there and I missed it, how many miles are on the motor?
    David Luney - Suwanee GA
    miatastuff@bellsouth.net
    2004 RX-8, 2005 MCS, 08 Red GT, 1992 Spec Miata and a parts car or two.

  4. #4
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    I'm trying to track down some heavy white smoke during early morning startups that disappears when warm.


    valve stem seals
    92 Italia "Competizione Speciale". 91 BRG "Judy", '69 Corvette "Mojo". '14 F150 Coyote 5.0. Looking for something blue.

  5. #5
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    Quote Originally Posted by miatastuff View Post
    Sorry if it's in there and I missed it, how many miles are on the motor?
    No I didn't think to include it sorry. The engine is sitting at 169k.
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  6. #6
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    Quote Originally Posted by Dynra Rockets View Post
    valve stem seals[/COLOR]
    Nuts. I know I've posted about how easy it is to change those before. And I just finished a TB/WP job a few months ago lol.

    Probably look at changing those when I get around to changing the headgasket then. Don't think i wanna fuss around with trying to keep the valves from falling in while trying to change the seals with the head on. Unless the consensus is I need to redo the check again?
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  7. #7
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    Throttle body needs to be open, I wouldn't trust the compression numbers without that. I've found its easier to pull the CAS plug.

    Next time you do it - do a cold compression test, then a hot one.
    Last edited by iscariot; 12-31-2017 at 06:00 PM.

  8. #8
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    Quote Originally Posted by iscariot View Post
    Throttle body needs to be open, I wouldn't trust the compression numbers without that. I've found its easier to pull the CAS plug.
    Sorry forgot to mention that the CAS plug was also pulled.

    Will try tomorrow when theres light out and do a cold then hot with the throttle open. This time Ill crank for a solid 5 seconds as well. Not sure if that will make much of a difference? Would imagine the engine rotates 720 with the double 3 second pull but Ill give it a go.
    Last edited by Otaroko; 12-31-2017 at 06:03 PM.
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  9. #9
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    CAS plug is all you need to pull - with no cam/crank signal, no fuel is injected. Smoke was probably residual vapor.

  10. #10
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    It hopefully will. There are 3 basic compression tests - cold, hot, and with oil. If you dump a teaspoon of oil down the spark plug, it'll help the piston rings seal, increasing compression. If the compression on a low cylinder doesn't increase with oil, that generally points to valves / head gasket.

    Other notes - your plugs look good, don't see any pepper on the porcelain. White would indicate lean going by old haynes manual identifications that were written for carbureted cars, but in truth most modern sparkplugs look like that.

    Miata-wise, 160-170psi across all cylinders is pretty healthy. Gauges are somewhat infamously inaccurate, so you're mostly looking for roughly the same number across all cylinders.

    White smoke, combined with our cold snap - possibly just water in the muffler.

  11. #11
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    Agree with the above. If it's running well and not consuming oil, drive on.
    David Luney - Suwanee GA
    miatastuff@bellsouth.net
    2004 RX-8, 2005 MCS, 08 Red GT, 1992 Spec Miata and a parts car or two.

  12. #12
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    Quote Originally Posted by miatastuff View Post
    consuming oil
    It is, which is what has had me monitoring everything for a while now. Really only consumes a lot when I do interstate driving, so 70-80mph or so sustained is what eats a bunch of my oil. But I dont see it smoking or anything. Regular driving to school and back which is 55ish or so and I find I dont burn through it anywhere near as quick.
    1996 White--MAGNAFLOW Catback--Illumina/FMSprings--Rev-G Frame Rails--Direzza Star Spec--TWM Big Type R Shifter--CIBIEs w/ OSRAM NBreakers--Nardi Comp Leather 330mm

  13. #13

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    110K on my clock and I also burn oil during highway cruising/trackdays. My compression numbers came back solid with #4 being a little low and I had solid dyno numbers. Don't worry about it, just add what's needed every now and then and keep going.
    '00 Black NB, Track/Street car.
    It seems like the most powerful weapon in the universe is speed. Move something fast enough and it will obliterate anything

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