81, blue smoke on overrun only?
04-25-2011, 05:49 AM
#16
Racer
Thread Starter
thats very interesting sounds exactly like what i'm getting,my trip was in mountain area so lots of long downhill stuff!i did the same after i noticed it just popped it out of gear and rolled down the declines instead.don' think ill get into this one unless something else comes up with the motor and it needs to be overhauled.thank you
04-25-2011, 06:00 AM
#17
Racer
Thread Starter
It's possible, however doubtful. Try loosening the oil cap or just remove it and make the same drive if possible. See if the symptom persists. If the problem goes away, then you found your problem, if not... Well. Keep digging I guess.
I saw something similar to this happen on an old 80's Corvette because the owner filled it with 0W20 oil, the oil was too thin for his old motor. I'm not comparing the two vehicles, I'm just relaying a past experience.
I know old oil will burn even in a tight motor when it's past it's change. Royal Purple is one that comes to mind. Everytime I've used it, it starts to burn in about 3-
When you get it figured out, let us know.
How many miles on your car?
I saw something similar to this happen on an old 80's Corvette because the owner filled it with 0W20 oil, the oil was too thin for his old motor. I'm not comparing the two vehicles, I'm just relaying a past experience.
I know old oil will burn even in a tight motor when it's past it's change. Royal Purple is one that comes to mind. Everytime I've used it, it starts to burn in about 3-
When you get it figured out, let us know.
How many miles on your car?
04-25-2011, 06:09 AM
#18
Racer
Thread Starter
Valve guides in a 928 are relatively short, and when they wear they allow wobble of the valve as the bore of the guide wears more at each end. My guides (82 Euro) were within factory wear limits at the defined valve lift, but I regarded that wear as excessive with 'waisting' of the guide bore, and fitted new guides and stem seals. Prior to this I was getting similar minor oil burn on the overrun (my motor had 230,00km on it). Some discussion on a thread I started here confirmed my thinking on what should be regarded as the wear limit (less than WSM).
At the mileage you have your guides are likely to have similar wear, combined with hard stem seals.
At the mileage you have your guides are likely to have similar wear, combined with hard stem seals.
04-25-2011, 06:12 AM
#19
Racer
Thread Starter
does anyone know if this model 81 euro even has a gauze ie metal wire ball inside one of the breather pipes that could become blocked with old dried oil ???????
04-25-2011, 07:56 AM
#20
Rennlist Member
BTW ... oil burning on mine wasn't fouling the plugs or coking the intake valves, it was just annoying ... which may be why Porsche set the wear limit at a greater number. You could try an additive, but beware that there may be other spin off effects in other parts of the motor.
04-25-2011, 08:22 AM
#21
Racer
Thread Starter
82 euro doesn't .. and I'm not aware that the 81 is any different.
BTW ... oil burning on mine wasn't fouling the plugs or coking the intake valves, it was just annoying ... which may be why Porsche set the wear limit at a greater number. You could try an additive, but beware that there may be other spin off effects in other parts of the motor.
BTW ... oil burning on mine wasn't fouling the plugs or coking the intake valves, it was just annoying ... which may be why Porsche set the wear limit at a greater number. You could try an additive, but beware that there may be other spin off effects in other parts of the motor.
04-25-2011, 08:46 AM
#22
Rennlist Member
Oil consumption figures in the user manuals might be acceptable to Porsche but seem excessive, and are unacceptable to me.
Oil consumption occurs as a consequence of varying factors on the 32 and 16V motors, but can be improved with alterations to crankcase venting, and other measures. With the standard crankcase venting on a Euro, oil mist has a short run through to the vacuum point on the plenum and tends to accumulate as a puddle at the bottom, until WOT and you get the familiar white puff, from that puddle being ingested by the motor. You may be noticing an element of this with your problem.
This is different to valve stem leakage which occurs more noticeably on overrun, followed by WOT, or increased throttle.
Oil consumption occurs as a consequence of varying factors on the 32 and 16V motors, but can be improved with alterations to crankcase venting, and other measures. With the standard crankcase venting on a Euro, oil mist has a short run through to the vacuum point on the plenum and tends to accumulate as a puddle at the bottom, until WOT and you get the familiar white puff, from that puddle being ingested by the motor. You may be noticing an element of this with your problem.
This is different to valve stem leakage which occurs more noticeably on overrun, followed by WOT, or increased throttle.
04-25-2011, 09:22 AM
#23
Racer
Thread Starter
Oil consumption figures in the user manuals might be acceptable to Porsche but seem excessive, and are unacceptable to me.
Oil consumption occurs as a consequence of varying factors on the 32 and 16V motors, but can be improved with alterations to crankcase venting, and other measures. With the standard crankcase venting on a Euro, oil mist has a short run through to the vacuum point on the plenum and tends to accumulate as a puddle at the bottom, until WOT and you get the familiar white puff, from that puddle being ingested by the motor. You may be noticing an element of this with your problem.
This is different to valve stem leakage which occurs more noticeably on overrun, followed by WOT, or increased throttle.
Oil consumption occurs as a consequence of varying factors on the 32 and 16V motors, but can be improved with alterations to crankcase venting, and other measures. With the standard crankcase venting on a Euro, oil mist has a short run through to the vacuum point on the plenum and tends to accumulate as a puddle at the bottom, until WOT and you get the familiar white puff, from that puddle being ingested by the motor. You may be noticing an element of this with your problem.
This is different to valve stem leakage which occurs more noticeably on overrun, followed by WOT, or increased throttle.
04-25-2011, 06:52 PM
#26
Racer
Additives are bad news... A "Mechanic in a bottle" is rarely the answer. If the oil consumption is acceptable, you can try to live with it, or it may be time to take things apart.
04-27-2011, 09:51 AM
#28
Racer
Thread Starter
dont know that adding a little additive could be classed as masking the problem what harm can it do, if it worked it saves an engine pull?i dont even know if this is the problem yet but if it is and it doesnt work and the fault annoys me i would have no problem overhauling the motor!
04-28-2011, 08:01 AM
#29
Rennlist Member
dont know that adding a little additive could be classed as masking the problem what harm can it do, if it worked it saves an engine pull?i dont even know if this is the problem yet but if it is and it doesnt work and the fault annoys me i would have no problem overhauling the motor!
Maybe there might not be a problem with a particular additive ... but what if there is? I've used additives in motors which are clearly stuffed and beyond redemption to buy more time ... but I won't use them in what is basically a sound motor and risk creating a problem.
04-28-2011, 10:32 AM
#30
Racer
Thread Starter
its b#rdahl they produce oils aswell dont think they would have a product on the market that could cause damage.as for thinning the oil, you are talking about a small bottle in nearly 2 gallons of engine oil.