99 deville/Northstar
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Northstar Engines and System Technical Discussion Discussion, 99 deville/Northstar in Cadillac Engine Technical Discussion; My Northstar did something strange yesterday. I slowed down to go through a toll booth, when I left the toll ...
  1. #1
    imaddicted2u is offline Cadillac Owners Member
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    Question 99 deville/Northstar

    My Northstar did something strange yesterday. I slowed down to go through a toll booth, when I left the toll booth there was a cloud of blue smoke left behind. I drove a bit further and there was no oil smoke. I slowed to exit the highway and another big puff of smoke was behind me. I drove through town and no blue smoke. Now I know the engine is using some oil, about a liter every thousand miles, but I have never seen a cloud following me. The engine runs strong, no signs of troubles as of yet. I've only had this Deville for a couple of months and it works great. Considering there is 547,000 Kms, Yes I said 547,000 Kms, on it the ride and handling are good. I don't know if the engine is original or not but it runs smooth and is clean. I can't see any sign of oil smoke at idle either. If it does actually have 547,000 Kms on it I think it deserves a drink of oil. There doesn't seem to be any substantial amount of oil leaking, no drops under it after it sits. The engine was spark knocking under light load before I noticed the puffs of blue smoke. I figured it was the 89 octane I put in it instead of the 91 or 93 that I usually use. I added a bottle of octane booster and the knock went away. When it knocked the knock would go away if I slowed or sped up slightly. So, on the 50 mile drive home, "I drove it like I stole it" and didn't see any oil smoke following me. I would think that if the engine had internal trouble it would smoke all the time. Any ideas as to what might have caused it to smoke in the first place.
    thanks

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  3. #2
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    kilometers or thousand miles?

    Either way, that IS a lot of mileage. All things get worn down with use... My bet is that your oil useage is due to not "exercising the rings", i.e. not frequently taking the engine to 6000+ rpm. What happens then, is you get carbon build up, and then the rings start to stick, and then you use more oil, and then you get MORE carbon, and you use more oil.... etc... in a horrible cycle.

    My recommendation to you, is to follow GM's procedure for removing the carbon. I'll post it in a bit.

  4. #3
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    Hmm... well I can't copy/paste, so I'll have to type it up.

    Before considering major engine repairs, the technician should perform the following procedure to clean carbon from the engine combustion chambers.
    Note: This procedure must be strictly followed. Hydrostatic lock may result causing severe engine damage if this procedure is not strictly adhered to. (that's important.)

    1) Obtain one can of GM TOP engine cleaner (TEC) P/N 1052626.
    2) Start the engine and bring the engine coolant temp to 200 degrees on the instrument panel gauge. (220F on a scan tool)
    IMPORTANT: Do not raise the engine speed above idle
    3) with the engine idling, disconnect the PCV hose from the PCV valve and slowly spray the TEC into the end of the hose.
    4) Raise the engine speed to approximately 2000 rpm until you see a cloud of white smoke coming out of the exhaust pipe, then shut off the engine.
    5) Let the vehicle sit for at least 20 minutes, preferably overnight. This allows time for the TEC to act on the carbon deposits.
    6) Once the soak period has been completed, start the engine and proceed to remove the remainder of the TEC from the engine by increasing the engine speed to 2000rpm until the white smoke has diminished.

    I recommend you follow that advice, and make SURE you get the aerosol can of TEC. It's much less likely to hydrolock the engine, and you can't pour it in too fast like you can with the bottle. After you finish the above, take it on a highway on-ramp, and with the shifter in 2nd, floor it. You can further exercise the rings by letting the car speed drop to 30mph, and flooring it back up to 60....

    Oh, you're going to want to change your plugs after you do this. A lot of crap gets moved around, and some of it can collect in the plugs, shorting it out.

  5. #4
    imaddicted2u is offline Cadillac Owners Member
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    Re: 99 deville/Northstar

    Excellent information, I thank you. I'll get the cleaner as soon as I can and carry out the instructions to the letter. I did excercise the rings on the trip back home with the transmission in 2nd as you described. The car seems even stronger after doing that. I got a sweet deal on this car when I got it due to the high kilometers. I paid $3500 canadian dollars for it and I just couldn't pass it up. The same year is selling for $13,000 to $15,000 canadian dollars around here.
    again,
    thanks to you Eldorado1

  6. #5
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    No problem. It may not entirely fix your oil consumption (in the event the carbon scored everything up), but it will certainly help. It should get rid of the knocking however, and it will run like $1,000,000 US (or the canadian equivalent) afterwards.

  7. #6
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    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 99 deville/Northstar

    An engine that puffs blue smoke after idling or deceleration usually has worn intake valve guides or valve guide seals. Under conditions of high intake vacuum, oil is drawn past the guides and into the intake. When given the throttle to get back up to speed the accumulated oil is drawn into the combustion chamber and burned. In a pushrod engine this can be fixed without removing the heads but a DOHC engine requires the heads be removed. The condition doesn't hurt anything but it does make your Caddy look like a polluting junker.

  8. #7
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    Quote Originally Posted by dkozloski
    An engine that puffs blue smoke after idling or deceleration usually has worn intake valve guides or valve guide seals. Under conditions of high intake vacuum, oil is drawn past the guides and into the intake. When given the throttle to get back up to speed the accumulated oil is drawn into the combustion chamber and burned. In a pushrod engine this can be fixed without removing the heads but a DOHC engine requires the heads be removed. The condition doesn't hurt anything but it does make your Caddy look like a polluting junker.
    Why would the oil go into the intake? The higher vacuum has to be in the cylinder for air to travel from the intake into the cylinder. So under idle conditions, it would just drip down the valve and get sucked into the cylinder, and be burned. There's no way it's going to collect in the intake unless your engine's on it's side or something... Typically bad valve seals will show up as a puff of smoke on startup.

  9. #8
    imaddicted2u is offline Cadillac Owners Member
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    Re: 99 deville/Northstar

    I went to my local dealer today and they never heard of Top engine cleaner. They sold me combustion chamber cleaner #993026. Is this product the same? Perhaps the part# is different in Canada. Anyway I put it in the engine and I guess I'll see what happens. It says to leave it in for 15 minutes but I will leave it in overnight. I hope that's ok.

  10. #9
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    Ranger is offline Cadillac Owners Member
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    Re: 99 deville/Northstar

    Same product. Don't forget to change the oil afterwards as that stuff will seep down past the rings.

  11. #10
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    Quote Originally Posted by imaddicted2u
    I went to my local dealer today and they never heard of Top engine cleaner. They sold me combustion chamber cleaner #993026. Is this product the same? Perhaps the part# is different in Canada. Anyway I put it in the engine and I guess I'll see what happens. It says to leave it in for 15 minutes but I will leave it in overnight. I hope that's ok.
    Ahh, my apologies... I don't think they have the aerosol in canada... Not sure why, could be some customs related thing.. As long as you followed the directions above/on the can, you should be fine.

    Leaving it in overnight is the best idea, but as ranger mentioned, it does seep past the rings (cleaning them on the way past), and contaminates the oil, so you're going to need to change it soon.

  12. #11
    BASSIN4FUN2003 is offline Cadillac Owners Member
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    Re: 99 deville/Northstar

    you might want to check the fuel regulator also to see if it is leaking fuel.it will cause the same blue smoke when they first start leaking,just pull the vacuum line off while running and see if fuel starts spitting out of it.

  13. #12
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 99 deville/Northstar

    eldorado1, only a very small amount of air travels through the intake system when the throttle is closed during either idle or over run. The high vacuum condition pulls oil past the valve guides and the oil accumulates on the valve stems and under the valve head because air flow is insufficient to carry the oil on through. When the throttle is opened up there is immediately much more air through the intake passage plus a washdown of fuel from the injector that carries the oil through to the combustion chamber where the oil is burned and produces blue smoke out the exhaust for a short period of time until it is all consumed. Unlike with worn rings, the blue smoke is not present as you cruise down the road because you no longer have the high vacuum condition in the intake with the throttle open. This is not an opinion or deduction on my part but straight from the aircraft engine developement engineers. An interesting side effect is that if the intake valve guides and seals are not replaced during overhaul enough oil can be drawn past the guides to prevent the proper breakin of the rings.

  14. #13
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    hmm... interesting. I personally only know of one instance of a smoking on decel problem, and that was due to poor ring seal, causing the oil to get sucked past the piston into the combustion chamber. Cure was to replace the rings. Like I said before, the only time a seal was suspected was for a puff of smoke on startup.

    With the kind of mileage Imaddicted has, just about anything is a possibility. Including the engine just being worn down.

    Any updates?

  15. #14
    imaddicted2u is offline Cadillac Owners Member
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    Re: 99 deville/Northstar

    Yea, sprayed the combustion chamber cleaner through the throttle body. I couldn't put it in through what looks like a pcv, located on the left side of the front valve cover. There was no vacuum on the hose or where it connects to the throttle body. Is that hose supposed to be the equivlent of the pcv if not what is it for? I feel vacuum on the grommet in the valve cover but not on the hose that plugs into it, is this normal? Should there be vacuum in the crank case? After letting the combustion chamber cleaner soak overnight I still intermittently get oil smoke. When it smokes I get a lot of blue smoke if I rev the engine in park and sometimes I don't. I get smoke sometimes when I pull away from a stop and sometimes not, sometimes when I decelerate and sometimes not. This seems strange to me. If the rings were worn out wouldn't it smoke all the time? Anyway soon after the combustion chamber cleaning I got a sluggish mass air flow sensor code and fuel mileage decayed. I sprayed the sensor with carb cleaner and so far haven't gotten the code back and the fuel mileage is getting back to normal. I think the combustion chamber cleaner fouled the sensor and hopefully the carb cleaner cleaned it. So far it looks that way. The engine still feels strong and runs smoothly. It gets good fuel mileage as well.

  16. #15
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 99 deville/Northstar

    The PCV is on the rear side of the engine, it goes to the middle (?) nipple on the top of the intake manifold. Sorry I didn't specify that before, I can see how it's easy to get confused. If the rings were worn out, yes, it would smoke all the time. It's pretty rare to get a northstar with worn out rings, they tend to last forever (partly due to their agressive wall hone and "oil consumption"). It still sounds like your rings are sticking to me.

    Just out of curiosity, did you spray the TEC through the mass airflow sensor? That would definately foul it up. It has a lot of oil in it that could coke the thin fragile sensor wire.

    I guess the real question is, did it get any better? Was it smoking all the time before? Or about the same frequency? How much of the TEC did you use?

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