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NA8 Compression check and Seafoam

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  • 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! :thud:
    1996 White Used and abused

  • #2
    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 Used and abused

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    • #3
      Sorry if it's in there and I missed it, how many miles are on the motor?
      David Luney - Suwanee GA
      [email protected]
      04 RX-8, 10 Black MS3, 08 Red MS3, 06 550i, 05 325i 92 Spec Miata and a parts car or two.

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      • #4
        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, '69 Corvette "Mojo". '14 F150 Coyote 5.0. Looking for something blue.

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        • #5
          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 Used and abused

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          • #6
            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 Used and abused

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            • #7
              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, 05:00 PM.

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              • #8
                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, 05:03 PM.
                1996 White Used and abused

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

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                  • #10
                    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.

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                    • #11
                      Agree with the above. If it's running well and not consuming oil, drive on.
                      David Luney - Suwanee GA
                      [email protected]
                      04 RX-8, 10 Black MS3, 08 Red MS3, 06 550i, 05 325i 92 Spec Miata and a parts car or two.

                      Comment


                      • #12
                        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 Used and abused

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                        • #13
                          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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                          • #14
                            So a little update on this. Car was slowly becoming more and more rough every morning I went out to start it. Finally said F it and tore into it to replace the head gasket.

                            Took the head down to the nearest machine shop which was all the way in Brunswick. (Cool heads up, no one does head work in Savannah anymore) After the shop cleaned up the head, and finished the valve job they pressure checked the head. There was the itty bitty tiniest of holes in the No. 2 exhaust runner FWD side where the head mold was cast together? You can see a cast line running along from the gasket flange towards the valve stem. MAYBE a sewing needle could have fit into that hole.

                            This explains the loss of coolant, rough stumbling in the morning as the O2 sensor is doused in silicates from steamed coolant, and tons of white smoke on start up.

                            First temp fix was 2000*F exhaust putty on the hole because I didnt know anyone here who could possibly weld such thin aluminum to begin with, and in such a tight spot, even with the valve removed. Knew it didnt work when I cranked the car up and there was coolant dripping out of both sides of the catalytic converter flanges lol.

                            Was able to find a mystery FM 99-00 head down in St. Augustine from Miata Bob. No idea whats done to it. If we knew who the original owner was FM could tell us what had been performed. Knew it was an early NB head as its got the CAS opening on the front of the valve cover. Cleaned up well enough. Threw it back together and we're golden. I'll have to replace the valve stem seals on this head at some point as its eating more oil now but it's not a priority ATM. Tried soaking the rings with different solvents while I had the head off but it doesn't seem to have helped or hurt anything really. Replaced the somewhat new-ish Koyo stock rad with a very nice CSF unit since it's much warmer down here in Savannah. As well as installed the Dayco hose ghetto Randall intake mod thing. The new M1 Hardcore Double Diagonal was a pleasant addition as well. Debating on removal of the A/C equipment since its too hot down here for it to work for more than a minute or so, to give the radiator less restricted access.

                            Question: Do all Illuminas squish? Have had the FM setup for a couple years now. (Illuminas, FM Springs, NB tophats) They've always made squishy sounds during compression after a speed bump, during railroad crossings and large depressions in the road. With the rougher roads down here Im noticing it more often and Im starting to question whether its time for replacement. Redline has the Tein SA Z's for a good price right now, but the consensus among the general public is that the FM setup is better? My only experience with Tein are the HA's??? I had on my NB6 in Oki and they seemed decent.
                            Last edited by Otaroko; 07-13-2018, 10:16 PM.
                            1996 White Used and abused

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