Smoke from Oil filler cap?!

Kyle Saenz · 01-16-2012, 07:50 PM

I have a 3.2 carrera that has been turbo'd, it has ran trouble free for a few months, but the other day it started smoking like CRAZY and so i turned it off and looked in the exhaust and saw it was covered in oil. I fugured I had blown the oil seal on the turbo so i rebuilt it today. started it up and no smoke. whent for a 40 minute drive and all seemed well and it ran perfect, good vacuum, afr's, oil pressure ect. Pulled like it allways had. Then when i got home I popped the engine lid and saw smoke coming out of the oil filler cap... nothing crazy but it was definetely noticable. Also I have had the crank case hose that would normally go to the intake venting to atmosphere, (boost in the oil tank is a BAD idea) i have had it like this for a few months with no issues... So what gives? I havn't done a compression test but the car seemed to pull as hard as ever and run the same, plus vacuum was great.... I didn't add any oil to the car after i rebuilt the turbo, oil level should be around the lower 1/4 mark on the dipstick...
HELLLPPP!!!!

ivangene · 01-16-2012, 08:00 PM

to start with - the easy Q:

you are checking the oil with the motor at operating temp and running right? (level sounds right)

Kyle Saenz · 01-16-2012, 08:16 PM

yes, well i added about half a quart of oil 2 weeks ago and it read half way on the oil level gauge (has proved acurate in the past, and fully warmed up on a level surface of course) after pulling the turbo and rebuilding it some oil was drained and now its at about 1/4. I would love for this to be an oil level problem though...

Kyle Saenz · 01-17-2012, 06:16 AM

anyone? :/

lindy 911 · lindy 911's Garage

Some light smoking from the oil tank is normal I believe. Mine does it when it gets hot. Usually you don't see it because the oil tank is vented to the intake and it all gets burned. Smoking and then not smoking could be from oil overfill but what did the turbo rebuild reveal? Was the seal bad? What did you find that made you think it needed to be rebuilt?

redstrosekNic · redstrosekNic's Garage

My 911 smokes slightly when the oil cap is off, when I'm checking the oil. I'm pretty sure it's normal.

JohnJL · 01-17-2012, 10:10 AM

Moisture evaporating from the oil? As the car cools down moisture from the atmosphere condenses inside the oil tank. Does it still do this after an extended run? Like 60 minutes after the thermostat has opened?

dshepp806 · dshepp806's Garage

I've never seen smoke coming from the oil fill line (my 1989) even on the hottest days.

,..not that this means anything relative to a turbo.

Something sounds a bit warm?

Best,

Doyle

Kyle Saenz · 02:49 PM

hmm. The turbo definetely needed rebuilt, the oil seal was bad and oil was all over the inside of the straight pipe. I don't think it used to smoke from the oil filler cap before the turbo build but i could be wrong. The engine has about 40k on it after a full rebuild. I am just worried its a cracked piston or blown ring, since i run boost.... still seems to run normal though. I guess i should get a compression test so i can at least know my engine isn't broken haha. Would a cracked piston or blown rings even cause smoke to come out of the filler cap? Pretty sure this in't just condensation either, it's a fair bit of smoke (nothing crazy, but i wouldn't call it light either) and it was still doing it after a 50 minute drive today.

TimT · 01-17-2012, 03:04 PM

Is this with the cap off when you are checking the oil? Some vapor/smoke is normal...

What you don't want to see is that smoke pulsing...... puff puff puff puff... that is a sign of blow by

Kyle Saenz · 01-17-2012, 03:12 PM

...yeah its puffing a bit.... some is even puffiing through the cap..... uhg.... shouldn't it be down on power if it was blowby though?! (i'm probably in denial at this point...)

Joeride9 · 01-17-2012, 03:32 PM

I just did a turbo conversion following your thread. What kind of boost you running? I am running 5 psi

Kyle Saenz · 01-17-2012, 03:53 PM

haha very cool! glad my thread helped you out. I have been running 7psi non intercooled. I know i have not had detonation or anything like that, my afr's have been in check and i don't boost for prolonged periods of time. I don't feel like this is something related to the turbo... Even if it is I know a lot of people have gone many trouble free years after adding a turbo to their 3.2... maybe the "full" rebuild i was told it got was not legit, i will look through my paperwork, because there is 140k on the body and if that much was on the bottom end i wouldn't be superised if the ring(s) quite on me... uhg someone please tell me they had this same problem and replaced some $5 gasket!!!! I'm don't want to have a blown engine

TimT · 01-17-2012, 04:01 PM

There are varying degrees of blow by... Ive seen some engines that literally blow smoke rings out of the filler pipe.... If you are just getting teeny reversions..keep driving..smoke rings... start saving your dinero

You should do a leak down test rather than a compression test.. You can isolate whether the problem is with the intake or exhaust valve, rings, and possibly other areas..

Kyle Saenz · 01-17-2012, 04:10 PM

okay, well I will probably take it to a shop and have them test it asap. If it is bad blow by am I going to hurt it more if i continue driving it, or will it just not run as eficient and burn oil but still last a while? (at least in you expeiriance, I realize each car is different, and we still arn't even sure that's the problem...) If it can last until tax returns I will be good to go, but if not i will be in a bit of a pickle...(its my dd)

911pcars · 01-17-2012, 05:49 PM

If it's blowby (sounds like it is), the only path from the combustion chamber to the crankcase is via the rings or a damaged piston. I'd perform a compression test first. It's faster and can pinpoint a weak cylinder for a more definitive leakdown test.

Sherwood

Kyle Saenz · 01-17-2012, 06:29 PM

Yes i will get a compression test done asap, I did just talk to a tuner friend of mine (I know, completely different realm, but he has built 2 600+hp dsm's and knows what he is doing when it comes to engines.) and he said with his turbo cars that if he vented the crankcase to atmasphere he would get smoke like i was saying, but when he connected the crank case vent into the intake BEFORE the turbo (always a vacuum situation) that the problem went away completely. This sounds like a good idea to me and i'm not sure why it never occured to me before. I will be doing this asap as well.
Thanks for the help guys and hopefully the compression test results turn out good! I will keep this thread updated with whatever happens.

911pcars · 01-17-2012, 08:04 PM

Quote:

Originally Posted by Kyle Saenz

Yes i will get a compression test done asap, I did just talk to a tuner friend of mine (I know, completely different realm, but he has built 2 600+hp dsm's and knows what he is doing when it comes to engines.) and he said with his turbo cars that if he vented the crankcase to atmasphere he would get smoke like i was saying, but when he connected the crank case vent into the intake BEFORE the turbo (always a vacuum situation) that the problem went away completely. This sounds like a good idea to me and i'm not sure why it never occured to me before. I will be doing this asap as well.
Thanks for the help guys and hopefully the compression test results turn out good! I will keep this thread updated with whatever happens.

Crankcase blowby, there's always a slight amount, normally vents into the intake anyway. However, the vent location (atmosphere or intake) doesn't cure the source of the blowby, only the symptom of compression loss. FWIW, aftermarket turbo engines often suffer damage from either excessive boost pressure and/or spark advance. Some engines still have higher-than-recommended compression ratio which exacerbates the above. Rings and pistons take a beating as a result.

BTW, if the crankcase venting path doesn't adequately separate oil droplets from the blowby fumes, the intake tract and probably the combustion chamber will eventually build up a layer of oil residue (carbon).

MHO,
S

Kyle Saenz · 01-18-2012, 04:56 PM

okay well under normal driving conditions (no boost) the turbo blew its oil seals again today. LOTS of oil is in the exhaust pipe... again... I really need to get on that compression test... it seams like there is definitely pressure in the crankcase but i don't understand with it venting to atmosphere why it would still be enough pressure to push oil past the seals in the turbo.... Is there something I'm missing here? I almost want to convert it back to stock and see if my problems go away... well bottom line is i need to get it flat bedded somewhere to do a compression/leakdown test. If it's in spec i will be completely baffled...

smurfbus · 01-18-2012, 07:55 PM

How is your turbo oil outlet routed? You may need better scavenging and sump for that line if its only fed to the crankcase sump or right chain cover.

The 930 has a mechanical scavenge pump (driver side cam driven) to get rid of the oil after the turbo and if that pump fails the oil makes its way past the turbo shaft seals and/or to the intake via the turbo sump breather.