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Thread: 69S with strange smoking engine problem - help.

  1. #1
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    69S with strange smoking engine problem - help.

    I recently purchased a '69S and am trying to figure out why the engine is smoking. When I initially made contact with the former owner, he told me he had a dealer rebuild the engine back in the 80s and it ran fine with no major smoking problems until 2 yrs ago when he took the car to a 10 min oil change place. He had the oil changed and the car came back smoking like a freight train. He then parked the car in his garage and it hasn't been driven until a couple of months ago.
    The first time I looked at it, it was blowing a little black smoke, no gray or blue smoke - I figured it was running too rich. I then inspected the car a second time prior to having the engine looked at it was smoking like a chimney - clearly burning oil. We shut the engine down and I sent it off to be inspected.
    Well, I had a leak down test performed with all cylinders between 4-6% . I went ahead and made a deal on the car. Several small oil leaks have been repaired and it was thought that maybe it was overfilled and oil had made its way to the muffler and it was buring it off. This doesn't appear to be the problem as the car has been run several times over the past couple of weeks as general maintenance items have been taken care of.
    Now, sometimes it blows smoke like crazy and other times nothing. Any ideas what could be causing oil to be burned periodically and not continually? I know that valve guides could still be worn even though it has a decent leakdown, but is there anything else that could result in these strange symptoms? Any replies are much appreciated.
    Robert

  2. #2
    Senior Member BBausser's Avatar
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    My 67S has a similar problem. I think it's leaks on the heat exchanger that eventually burn off. It goes to the resto shop this week and hopefully in a year or so won't be a problem no mo
    Currently:
    67 3.6 Rocket "Silver"
    62 T6 Outlaw Coupe "ole Yellow"
    65 F100 Custom Cab Flairside Shortbed

    Gone but not forgotten in last 2 years:
    67S Concours King
    67 912 Vintage Racer
    68 912 Flipper
    83 911SC
    93 Mo30 968

    too many cars before that

    Early S Registry # 787
    R Gruppe # 551

    "its better to wear out then rust out"

  3. #3
    Worn or Broken oil ring or intake valve seal gone bad.. You'll have to isolate the problem by inspecting each plug to see whiich is the oily one.
    Also,, make sure the air cleaner breather line to the oil tank is not switched with the crankcase breather line to oil tank. This could cause the problem as well creating pressure in the engine case and forcing oil past the rings.

    Robert..

  4. #4
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    I appreciate the replies, I will pull the plugs and take a look.
    Robert

  5. #5
    Have you checked the oil level?
    I know that sounds like an odd question, but, if the oil has been over-filled, then it can cause foaming of the oil, pushing it into the air cleaner and causing smoking. This will normally occur if the engine has been driven hard. I have seen it happen if the oil is severely over filled. These people should NOT be allowed in the same hemisphere as a 911!

  6. #6
    Ditto on Mike's thoughts. The oil tank can be over filled and this condition often times will not make itself apparent until the oil gets warm and expands and then is pushed out where ever it can go, usually into the air filter box.

    You didn't mention oil temperature. Is the oil/engine getting hot???
    Check the engine thermostat...a real hassle...they do fail and cause heating/smoking.
    Ed Barnett
    RGruppe #124
    Northern California Racing Club
    American Racing Club
    Member, Northwest Hillclimb Association

  7. #7
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    I just picked up the car and was told it was probably an oil ring(s). Oil changed and it is definitely not overfilled. Went to get gas with engine cold, no smoke at all. I let it idle for a few minutes and nothing. Then I ran it down the highway and warmed it up. At about 3000 rpms, it's smoking like a freight train. When it returned to idle, it is smoking like crazy.
    Any other thoughts?
    Robert

  8. #8
    1969 912 Targa Soft Window #0053 69-912-Targa-SW's Avatar
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    How about old oil and junk inside the muffler. Try getting it out on a long run for about 1/2 hour and get it burned out. Just make sure theres not any bad noises in the motor. I think it has been sitting and just needs to be driven.
    Good luck, Bill
    Bill Kent
    1969 912 Targa SWT
    #0053

  9. #9
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    Thanks to all for the suggestions. I will try running the snot out of it and see what happens.

    On another note, I just let it idle now for about 10 min., I then revved it up to about 3-4K a few times and no smoke at all. None! This is really strange. Maybe it is sucking oil into the engine when it is hot and under load? I will keep looking.

    Thanks again.
    Robert

  10. #10
    It's oil in the muffler.

    This happens all the time when people that aren't familiar with 911s (i.e. oil change places) over fill the oil tank. The excess oil gets sucked into the intake through the breather hose and gets deposted in the intake, exhaust and muffler. The exhaust burns out fairly quickly but the muffler collects a lot and doesn't start burning the oil until after the motor has been run long enough that the muffler finally reaches the temperature that will burn the oil out.

    If you want to expediate the process you can take the muffler of and pour out the oil. I would not use any flammable solvents to rinse it out unless you can be sure that it is completely evacuated of vapor before you place it back on the motor.

    You might also take the air filter out of the air box and clean the oil out of the air box.

    I'm pretty sure your motor is fine. There's no reason to suspect anything like rings unless the motor was pinging a lot.
    Bobby
    71' Olive 2.2E Targa / Early S #491

    I've always considered the glass to be half full...that is until I reached middle age and realized that it is actually half empty.

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