FetalEcho

Noticed oil under right passenger rear, seems to seep off a rubber hose and onto the floor. Slow leak, maybe one drops a day.
Checked this forum, some have mentioned it may be the turbo boost hose seal (or something like that).

Took it to dealer today, they said oil separator needs replacement. No mention of turbo hose seal or gasket..etc.
Does this make sense?
Service manger didn't seem to know much about this and just conveyed to me what the technician's assessment was.
If so, is it a major job to replace the separator?
Thank you.

911dude41

Common occurrence. Search "right side turbo lake". If you take that hose off, chances are there will be oil pooled up in the bottom of the hose. I used to disconnect, drain oil from hose and reconnect. I bought an air/oil separator from Vektor but it was only for the 991.2 Carrera, not the Turbo S. You can rig up your won oil catch can.

I went aftermarket hoses and just tightened the clamp to hell. No more leaks.

FetalEcho

Car is CPO so will be fixed by dealer. They ordered the air/oil separator. So replacing the oil separator is the fix?

911dude41

Unless they're installing some revised part it will still happen.

CodyzWorld

Just had mine done at 30K. Doesn't leak enough to add oil, but thats a must fix asap.

If you drive with vigor, make sure you dont overfill the oil. I keep mine at 70% full. I'm sure others would chime in here.

worf928

Yes. As has been posted above it’s a common ‘thing.’

It is located in the least accessible place in the engine compartment. I looked at the shop manual steps which include “remove intake.” My WAG is 10 hours of labor at least. And every gasket dislodged should be replaced. Along the way you might as well have them do all the scheduled maintenance due in the next 3 to 4 years *if* they will charge you only the incremental expense which should be mostly just the cost of parts. (PDCC bottle, drive belt. Spark plugs too, but not all common labor for the plugs.)

Yes and no.

Exactly. A new separator will simply reduce the amount of oil flowing from the separator to the intake.

I just empty the hose every year when I do my yearly oil change.

Regardless of how you drive (on the street) targeting 1/2 full on the gauge is far better than attempting to maintain the level at Max. I, personally, am happy to keep the level at one bar above min and keep a quart of oil in the frunk. I target two bars for fill but won’t add if it’s at one bar. Keeping the oil ‘topped up’ just makes it harder for the air/oil separator to do its job, broken or not.

I do about 3000 miles per year on my Turbo. I do not recall having to add oil between oil changes. And that’s 8 oil changes. Wow. I’ve had my Turbo for almost 10 years pretty soon.

This for typical ’street’ driving. If you are sustaining lateral G on a road course then do not apply my advice.

H2Owon

It could also be the hose coming off the passenger side intercooler which is often removed to facilitate spark plug replacement. They occasionally don't reseal properly due to the age of the seal and leave telltale drips coming off that hose after being driven. It will be a few drops after each drive and park cycle. The oil is coming from the turbo seal on the intake side and is normal. The fix for that issue is hose replacement given the seals are an integral component of the hose.

FetalEcho

Thank you all for your invaluable input. Much appreciated.

I think my oil level is one bar under max, last I checked. Would this alone lead to the oil leak, assuming everything else is intact?

I would hate them to take a million parts apart to reach the separator, for no real good reason to do so. Especially if the issue isn't the separator, but the intercooler hose as mentioned above.

And you guys said, it's a persistent/recurrent issue? So we should just expect and accept that these cars leak oil?

Thanks again.

CodyzWorld

That's what the dealer did exactly. Replaced the hose first. Then when it continued to leak, they changed the separator. At least now it's done and no leaks.

FetalEcho

And this would make sense because replacing the hose is easier (I think), and then you go to the more involved step once step 1 fails. I'm not sure why the tech(s) said separator and didn't think about hose, maybe because most likely that's what it is.

Problem is I have little confidence in dealership techs using logic and research in troubleshooting. I have to assume/hope that they know what they're doing.

I'll keep you guys updated as things move forward.

worf928

No.

Ok. Stop. Sit down and put on your thinking cap.

The system under discussion is the air intake system for the engine. (You know, fuel plus air and a spark makes a boom in the cylinder.) Theoretically, the intake system should not have liquid engine oil in it. Therefore if an intake hose is leaking engine oil, replacing the “leaking” hose is like changing soaked bandages on a head wound for fresh ones. The difference is that engine oil has no coagulant. Or, in other words, replacing a hose is treating the least important symptom. Or, in other, other words, replacing a hose is not even a basic attempt to solve the problem of “way-in-excess oil in the air inlet system.”

It is an issue with all post-70s cars. All cars put a little engine oil into the intake. It is not a ‘leak’ in the strictest sense. If you start here:

https://rennlist.com/forums/991-turb...l#post18126718

and look at my posts and responses to my posts, it provides a high-level overview of “crank case breather systems” and what’s going on in the 991 Turbo.

The issue is that CARB/EPA/TUV-compliant crank case breather systems are apparently “hard” and have been since the 70s. They all rely on some mechanism to separate engine oil from pressurized crank case gases which must be “reburned” in the engine. The oil is supposed to be drained back into the oil sump. The air/oil separator in the 991 has been through 3 (if not 4 revisions.) It appears that even when functioning perfectly it still allows enough oil to get past it and collect in the right side intake tract (it is supposed to expel relatively oil-free crank case gases into the right side.)

Now, if you have liquid oil in the left-side air intake branch then you have an actual leak as there is no “normal” mechanism that would allow engine oil into the left side. In that case, the leak could very well be an oil seal on the turbo. It’s also possible that the right-side turbo could leak, but leaking turbos seem to be rare based upon what folks report here. Bottom line is that on the right-side, oil “leaking from intake hoses” is most-likely to be the crank case breather system not adequately scrubbing oil. Replacing the separator should slow the accumulation of oil (and therefore reduce leakage) until the separator fails again.

I’ve done pretty extensive experimentation with the breather system on 928s (and would love to experiment on the 991 except that the separator is such a PITA to get to) and it’s a complex issue.

The right-side turbo inlet hose functions, essentially, as a catch can for the excess until it gets “clogged” enough for spoon-fulls of oil to get dragged past the turbo and into the hoses downstream. That seems to take 10k to 15k miles. Right now there’s no good way to keep excess oil out of the right side. So, my solution is just to drain the hose with every oil change and that seems to keep liquid oil from coating the after-turbo right-side hoses.

I am unconcerned with the ‘oil leaking.’ My concern is that engine oil is not fuel. Burning engine oil messes up the air/fuel ratio, causes carbon buildup on piston tops, and, with our DFI engines, will eventually put enough carbon on the back side of the valves to keep them from sealing perfectly and will speed deterioration of valve stem seals.

ottodawg

Common.. When I installed CSF IC's a few years ago, there was oil in the right hose, when I removed them this weekend, there was oil in the hose. Pretty sure oil level doesn't make much difference. I usually keep it about mid-level.

onfireTTS

The new hose has a secondary seal to keep the oil inside the hose.

ram_g

I recently took my 43k mile CPO 991.2 TTS in for exactly this and all the dealer did was to replace the hose.

worf928

The volume of crank case gas (also called blow-by) that the engine has to “exhale” is proportional to load. So, the more you’re flat-footing it around the harder the breather system has to work. If you’re running a tune then your working the system even harder when you floor it. Worn piston rings or poorly-sealing pistons will also increase blow-by. There may also be some “capacitance” in the breather system such that short bursts of heavy load don’t stress the breather system. If you’re just cruising along on the highway, engine load is very low and the breather system doesn’t have to do much work.

Oil level comes into play because of “windage.” Windage is how much the crank shaft, rods, camshafts, vavles, and pistons ‘churn up’ the oil in the crank case. (Imagine a blender ‘cause that’s what happens in the crankcase.) Typically, the higher the oil level the more “churn.” The churn is what ”dissolves” the oil into the blow-by gas thus requiring it to be separated from the gas before the gas can be reburned in the intake. The “churn” is load and RPM dependent.

Full-up race cars run a “dry-sump” with a vacuum pump sucking oil and blow-by gas out of the crank case thus minimizing windage. The effect of windage on any particular motor will be very dependent upon the locations from which the gas vents, routing and length of vent hoses, vent sizes, restrictions, etc.

If you look at the thread URL I posted above - there are a couple of pertinent posts per page for about 8 to 10 pages - SamboTT chimed-in with the “run a lower oil level” advice too.