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Diagnosing smoke, HG? Something else?

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  • Diagnosing smoke, HG? Something else?

    If anyone remembers, I posted a few months back that I suspect I have a blown head gasket. (The old thread is here: The summer has been busier than I anticipated, so progress has been slow, but I've done a few more tests, and I still have no idea what I'm dealing with.

    I did a compression test. I warmed up the engine, and as it came up to operating temp there was the familiar white smoke that keeps coming back, again only coming through the left of the two tailpipes. The smoke is white, and definitely doesn't smell like any burning motor oil I've ever smelled. It also doesn't smell sweet. I have never smelled burning coolant, but the smoke coming out has a terrible smell and makes it hard to breathe (it filled up the garage when the wind shifted direction)

    On the warm engine, the compression results were:

    Cylinder 1: 195
    Cylinder 2: 191
    Cylinder 3: 196
    Cylinder 4: 195

    As far as I know, the 5 psi difference between the lowest and highest readings is not a big deal, is that incorrect?

    Also, all the plugs looked good to me, with a brown color to them. None were wet, and none looked steam cleaned.

    After that, I decided that I would pressurize the cooling system, and see if it held pressure. I reasoned that since the smoke appeared when the engine was warm, it's possible that coolant is only leaking into the combustion chamber once it builds up pressure. I'm not sure how much pressure the system is supposed to hold, so I pumped the system up to about 15psi, not too high, but on the high side. It would bleed down to about 13psi, and then stabilize. I pulled the plugs, and looked into each cylinder, expecting to see coolant in one. I didn't, so I pressurized the colling system a couple more times, just to make sure that if it was leaking, enouch would get into the combustion chamber so that I could see it. Still nothing, everything looked dry in there. I turned the engine over by hand a few times, with the hope of sloshing coolant around in the combustion chamber so I could see it, still everything looked completely dry in there.

    So, I don't know what to do next. In my previous thread someone suggested that it's possible that I have bad seals in my brake master cylinder, and the engine is sucking in brake fluid through the vacuum booster. Does this sound like a possibility? If so, will removing the vacuum hose to the booster eliminate this problem?

    Thanks, and sorry for the long-winded post.
    1990 BMW M3
    1989 Porsche 951
    1988 Volvo 240DL

  • #2
    Well. if you want to know what burning coolant smells like, borrow a turkey baster and put a couple of ccs of coolant in it.
    let the engine warm up to operating temp, then "spill" a couple of drops on to the hot header. This will tell you what burning coolant smells like and not a poor air /fuel mixture being partially burnt.

    The only time you would be able to actually see coolant in the combustion chamber( an oven cavity?) is when the engine is stone cold and the gasket has been breached between a water hole and one of the combustion chambers. At this point, a pool of coolant in a combustion chamber would mean that the car has significant start/idle/driveability issues.
    Coolant in the cold combustion chamber would be seen as wetness, just like an over rich fuel mixture.

    I would suggest that you take the car to a pro.



    • #3
      Originally posted by Epic2112 View Post
      I did a compression test. ........

      On the warm engine, the compression results were:
      how did the plugs look when you did the compression test? any with an abnormal white residue?

      cheers, jason


      • #4
        I'm not an expert at reading plugs by any means, but they looked good to me. No white residue, they all had a rich brown color to them. Also, they all looked the same, I didn't see any variation that would suggest an issue in any particular cylinder.
        1990 BMW M3
        1989 Porsche 951
        1988 Volvo 240DL


        • #5
          Smoke can be attributed to all the oil and coolant left on the header.
          Fully Restored 1985 Corolla GT-S
          1987 328ci SR20DET Drift Car (Will Convert to M3 Spec soon)
          1989 Honda Civic Si-R Current Project
          2002 Corolla CE Daily Driver


          • #6
            What type of oil are you using? Mobil 1 synthetic oil burns greyish-white which could be valve seals, especially noticeable at a long idle or on decel. Member Eric used to have an Acura Legend that could easily fill an intersection if let idling for some time (i.e. drive through). Ultimately you need to do a leak down test.

            Originally posted by drinaldis
            I dated a girl who used to do the reverse grind. I kinda liked it.