maydog Posted March 7, 2005 Report Share Posted March 7, 2005 Howdy, I have noticed in the past few monthis that my 97 sts leaves a puff of smoke and a burnt smell when coasting / slowing to a stop from a high speed and then taking off again. It is really noticeable if I engine brake the car and then hit the accelerator. It is the worst after filling up the oil - I am careful not to overfill it. My car probably consumes 3-5 quarts of oil between changes (I use the oil life indicator, usually change around 10%). Is this problem indicative of a piston ring issue or could it be more benign like a bad pcv valve. Other than the occasional smoking, it runs like a champ. Thanks, md Link to comment Share on other sites More sharing options...
Bob D Posted March 7, 2005 Report Share Posted March 7, 2005 Howdy, I have noticed in the past few monthis that my 97 sts leaves a puff of smoke and a burnt smell when coasting / slowing to a stop from a high speed and then taking off again. It is really noticeable if I engine brake the car and then hit the accelerator. It is the worst after filling up the oil - I am careful not to overfill it. My car probably consumes 3-5 quarts of oil between changes (I use the oil life indicator, usually change around 10%). Is this problem indicative of a piston ring issue or could it be more benign like a bad pcv valve. Other than the occasional smoking, it runs like a champ. Thanks, md In the 'old school' that I come from, a cloud of oil smoke after hard engine de-aceleration is usually caused by worn vlave guides, or seals. (You would still have good ring compression, which would help pull oil down through the guides..) '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
JasonA Posted March 7, 2005 Report Share Posted March 7, 2005 In the 'old school' that I come from, a cloud of oil smoke after hard engine de-aceleration is usually caused by worn vlave guides, or seals. (You would still have good ring compression, which would help pull oil down through the guides..) That's what I was going to say...on a hard engine decel, you can get some oil sucked down to the cylinder with bad valve seals (or guides, or both). Yet, valve seal problems are apparently pretty rare on Northstar engines. I don't think we've had ANYone here with valve seal problems, and Bbobynski has stated that it's uncommon. But still, you can't argue with the facts, and if you get a noticeable puff of blue smoke, traditionally, valve seals would be a suspect. No puff on a cold or hot start? Your oil consumption seems on the high side of the tolerance, but within "normal" of what Cadillac accepts (1 qt/1000 miles) if you're doing 3000-5000 miles between oil changes. Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
Bob D Posted March 7, 2005 Report Share Posted March 7, 2005 Yet, valve seal problems are apparently pretty rare on Northstar engines. I don't think we've had ANYone here with valve seal problems, and Bbobynski has stated that it's uncommon. I know, Jason I was dubiuos too. Perhaps with the way the PCV is plumbed and operates on a Northster even a slight overfill might cause this? Although maydog did claim not to overfill... Hmm..You know, there is some discrepancy with Northstars as to where is full on the dipstick... '93 STS.. opened, dropped, wide...fast. Link to comment Share on other sites More sharing options...
pats37 Posted March 7, 2005 Report Share Posted March 7, 2005 How many miles on it and when did it start doing this? Link to comment Share on other sites More sharing options...
maydog Posted March 7, 2005 Author Report Share Posted March 7, 2005 The car is at 165K. The smoke i see from the car is whiteish - I have never actually been behind my vehicle when this is happening, I cannot tell if it is blue, but it definitely has a smell. I have never noticed a puff at startup, but it is winter so the steam could cover that up. I just rechecked the oil level hot, it is at 2 ticks up from the bottom marking of the dipstick. The car is on a small incline so I suppose it is at the halfway point on the stick. I never really notice the smoke when the oil level is lower, it may be there just not as strong. Maybe I should just add to 6.5 quarts each fill? I do not know when the trouble started, maybe a year ago? I usually forget about it until oil changes or top offs. Link to comment Share on other sites More sharing options...
JasonA Posted March 8, 2005 Report Share Posted March 8, 2005 Maybe I should just add to 6.5 quarts each fill? Honestly, that's what I would do. Good call! Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
maydog Posted May 13, 2005 Author Report Share Posted May 13, 2005 Hello again, What are the odds, I got a replacement engine with 65K on the clock and the same thing is happening? What could the issue be, i feel sorry for the folks behind me. I noticed most cars keep a pretty good distance from me when I am coasting, a nice safety feature I guess - but pretty ghetto. Stumped Link to comment Share on other sites More sharing options...
Scotty Posted May 13, 2005 Report Share Posted May 13, 2005 I just did some research and everything I find regarding smoke on deceleration is related to valve seals. The odd thing about that however is that Guru said that leaky valve seals are rare and here you have it on two engines. I didnt follow the thread about your engine is this a new engine for you? What kind of oil are you using? I would watch your level and make sure its not too high. What weight are you using? If you are using 5W30 or synthetic I would discontinue it immediately. Why don't you try some of that high mileage oil in 10W30 to see if you can condition the seals a bit. Read the benefits of this oil in this article from Valvoline: http://www.valvoline.com/carcare/articlevi...g=ccr20030901v2 I especially like this: Conditioned engine seals > Helps prevent oil leaks and deposit formation Link to comment Share on other sites More sharing options...
maydog Posted May 13, 2005 Author Report Share Posted May 13, 2005 The engine is new to me, it runs fine but the smoke is annoying. I am running wal-mart brand 10W-30 - maybe it is time for me to upgrade to some brand name stuff. I wonder if this condition is exacerbated by the lack of a catalytic converter, I asked the mechanic to install a new one during the engine swap, but he told me not to worry about it since there are no emissions tests. Link to comment Share on other sites More sharing options...
Ranger Posted May 13, 2005 Report Share Posted May 13, 2005 The engine is new to me, it runs fine but the smoke is annoying. I am running wal-mart brand 10W-30 - maybe it is time for me to upgrade to some brand name stuff. Maydog, I have been using the same oil (Supertech) for a few years now and have had no problems with it. I doubt the brand has anything to do with it. Link to comment Share on other sites More sharing options...
maydog Posted June 1, 2005 Author Report Share Posted June 1, 2005 I am updating this thread for posterity. The smoke dissapeared after I installed a new catalytic converter. I suspect that the converter somehow processes the smoke to make it less noticable or that the slight increase in backpressure reduces the oil burning. See my thread on the catalytic converter install for more details. Link to comment Share on other sites More sharing options...
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