Please help explain 930 engine smoke

LucaScali · 10:50 PM

I have an issue that is causing bluish white smoke to billow from around the driver's side rear wheel and the left side of the engine lid grill, particularly at idle. It seems to be coming from the end of the steel pipe/heat exchanger on that side.

There is no smoke from the tailpipe at startup or any other time, no unusual noise, and no discernible change in performance.

The oil return tubes on that side have long been a problem and seem to leak a lot more lately--I'm greeted with two parallel stripes when the car has been parked for even a couple hours. My guess is that oil is now steadily dripping onto the driver's side heat exchanger and steel pipes below.

Is it dangerous to drive the car with oil burning off from that area? Is this likely caused by the deteriorating oil return tubes as I suspect, or could it be something more sinister (I don't see any other obvious leaks)? Any guidance/advice would be appreciated. Thanks!

T77911S · 07-01-2015, 03:07 AM

just bad for the people behind you.

oil will help keep the back of the car from rusting out

twistoffat · 07-01-2015, 03:35 AM

Your guess is right. If the oil was being burnt of in the exhaust and you had a leaky heat exchanger then you would probably have it appear in the cabin with the heat on. Oil dripping onto the heat exchanger could catch fire so Its sensible to find the leak quickly. Have you checked your valve covers?

Tippy · 07-01-2015, 04:50 AM

If my car hasn't caught fire from oil dripping on the turbo headers, no one's will.

Now if it's running a lot, it may. But drips just vaporize.

tharbert · tharbert's Garage

Autoignition point of motor oil, according to a quick search, is over 750°F. So, it's vaporizing at flash point but won't catch fire until the vapor comes in contact with 760-870° which I think would be hard to do with all the air swirling around in there. Even a cigarette at full puff doesn't get hot enough to ignite motor oil.

jpnovak · 07-01-2015, 05:53 AM

If you have significant leaks on the oil return tubes then you need to take care of that. If the o-rings are failing and actually fail you will basically drain all the oil onto the ground. Bad things happen to engines that run out of oil.

So... Why don't you jack up the car and take a look to see where its actually leaking? There are lots of places where a 930 motor can leak on the rear DS of the engine. Cam towers, cam chain housings, turbo supply, turbo drain, turbo oil siphon tubes, etc.

LucaScali · 07-04-2015, 07:28 PM

Thanks, guys. It's still just a drip so far, so it's good to know there is no immediate safety hazard. Appreciate the warning about the tubes, jpnovak.

So letting the car idle or sit long enough now produces an erratic idle typical of a vacuum leak, which suggests twistoffat may be right about the valve covers. I'm going to take a closer look tomorrow, but it's probably time to replace the gasket, assuming the cover itself isn't warped.

Do I really need to drain all the oil to do this? Is it important to replace all the the hardware or can it be reused? Thanks again.

Last911 · 07-04-2015, 07:50 PM

Jack up the car on the one side. It should drip a bit, but not require an oil change. Great excuse to pop off that tire and have a closer look at what's happening.

Also check your CV boot. Mine ripped and the grease hit the heat exchanger somehow (or it was already there) and it was burning off. Smelled bad. Cleaned it up and it's all good now.

LucaScali · 07-06-2015, 08:50 PM

Thanks, Last911. So guys I took a look underneath and the valve covers do seem to be leaking in a couple spots, but that doesn't appear to be the immediate source of the smoke. Please take a look at the pics and let me know what you think. It seems to be caused by oil dripping from a nut to the left of the valve cover. You'll notice there is also a loose screw just hanging in the gap; not sure if it's supposed to be there.

In the center is the leaky nut.

Here is a closer look. Notice the loose screw above. Is that supposed to be there?

LucaScali · 07-10-2015, 08:11 PM

Any ideas? Would be nice to get rid of the embarrassing smokescreen.

ant7 · ant7's Garage

My Advice first would be to remove each valve cover and fit new gaskets and nuts, and make sure you torque them up with the correct procedure, if you still have the oil leak, then i would suspect it could be coming from the rear of the cam chain case, where it is mounted to the cam box, [had this on one of my previous 911's]
Good luck with it, and as others have said, unitill you know where the oil is coming from, i wouldnt drive too much! If something fails big time, you will lose all of your oil quite quickly, i have experience of this when one of the front oil cooler lines decided to let go, unbelievable mess, fortunetly, i was very lucky as i switched off the engine and dipped the clutch as soon as it happend.
A...

Quote:

Originally Posted by LucaScali

Any ideas? Would be nice to get rid of the embarrassing smokescreen.

onboost · 07-11-2015, 10:26 AM

Obviously you are not that familiar with these cars.. not knowing your mechanical abilities either. I would suggest;
1. That you find a good independent shop in your area and take it in and get the work/leak addressed.

Or

2. Tighten the valve cover bolts starting with the two center bolts and work your way to each end. Spray the left valve cover and heat exchanger with a good engine cleaner/degreaser and hose it down well and get the area cleaned-up. Drive the car a bit and see if it still smokes, or continues to leak. If not, great! If so, at least the area is clean and you should be able to get a better look at what's leaking, oil return tubes, valve cover, or possibly scavenge pump seal (which you can see in your pic.. follow the copper line).

LucaScali · 07-11-2015, 09:22 PM

Thanks, Ant. Appreciate it. Can anyone speak to the loose screw in the space above the leaking nut (which really seems to be fueling the smoke)? It's just hanging there.

LucaScali · 03:10 PM

I suspected that at least some of the oil was actually seeping down from the engine bay and, lo and behold, the spot just above the leak near the lower left corner was wet, and I found that the belt that drives the air pump and presumably the scavenge pump had snapped off.

Is it tough to get at the other end of the pulley to replace the belt? Is the snapped belt likely the cause of the oil collecting in that area or a symptom of a larger issue?

ant7 · ant7's Garage

The belt you refer to does not drive any oil pump!
I would first clean off the old oil, and check under the car with the engine running and try and get an idea of where the oil leak starts from, then investigate further.

Quote:

Originally Posted by LucaScali

I suspected that at least some of the oil was actually seeping down from the engine bay and lo and behind when I checked, the spot just above the leak near the lower left corner was wet, and I found that the belt that drives the air pump and presumably the scavenge pump had snapped off.

Is it tough to get at the other end of the pulley to replace the belt? Is the snapped belt likely the cause of the oil collecting in that area or a symptom of a larger issue?

LucaScali · 07-14-2015, 07:00 AM

Poor choice of words, thanks for correcting me, Ant. I meant the other end of the pulley, if I'm not mistaken, turns the scavenge pump. I saw a diagram where the the pulley linked the camshaft to the pump.

I've looked at it with the engine on and it's definitely originating somewhere in that area (drip from the nut pictured is certain, for what it's worth), but I'll do some cleaning and investigate further, as you suggested. Appreciate it.

ant7 · ant7's Garage

No Worries,
I realy would like to help further, but i have studied the picks above, and i cant seem to see the loose nut your refering to, from what i can gather, the oil leak is somewhere near the cross-over pipe of the exhaust as i can see the flexy part in the pick, is that correct, or is the oil dripping from behind the cam case, between the cam box ? the more info you can give us, the easier it will be for us to identify the leak!
A...

Quote:

Originally Posted by LucaScali

Poor choice of words, thanks for correcting me, Ant. I meant the other end of the pulley, if I'm not mistaken, turns the scavenge pump. I saw a diagram where the the pulley linked the camshaft to the pump.

I've looked at it with the engine on and it's definitely originating somewhere in that area (drip from the nut pictured is certain, for what it's worth), but I'll do some cleaning and investigate further, as you suggested. Appreciate it.

LucaScali · 07-16-2015, 01:02 AM

Took Ant's suggestion and with the engine running the problem became obvious. It's coming from the area encircled in red. No doubt. With the engine off, little if any oil can be seen leaking from there. Once the car is started, oil quickly begins to spill out of this area and stream along the housing, sending a steady drip of oil below. As the engine warms up, the exhaust pipes get hot enough to incinerate the leaking oil and, voila, persistent cloud of smoke coming off the pipes.

There is also a bit of oil coming from the area encircled in blue, even with the engine off, but it's very minor by comparison, and may be derivative.

In the yellow circle is the loose screw I was talking about. It seems to be just hanging there and I can easily move it around with my finger. Does it belong there?

So now what? Is there a seal that can be replaced or is the whole thing kaput? I haven't noticed any problems with the turbo. Is it easy to get at the seal?

onboost · 07:06 AM

Quote:

Originally Posted by onboost

2. Tighten the valve cover bolts starting with the two center bolts and work your way to each end. Spray the left valve cover and heat exchanger with a good engine cleaner/degreaser and hose it down well and get the area cleaned-up. Drive the car a bit and see if it still smokes, or continues to leak. If not, great! If so, at least the area is clean and you should be able to get a better look at what's leaking, oil return tubes, valve cover, or possibly scavenge pump seal (which you can see in your pic.. follow the copper line).

Quote:

Originally Posted by LucaScali

It's coming from the area encircled in red. No doubt.
There is also a bit of oil coming from the area encircled in blue, even with the engine off, but it's very minor by comparison, and may be derivative.

In the yellow circle is the loose screw I was talking about. It seems to be just hanging there and I can easily move it around with my finger. Does it belong there?

So now what? Is there a seal that can be replaced or is the whole thing kaput? I haven't noticed any problems with the turbo. Is it easy to get at the seal?

As I stated above, from your picture it appears to be the scavenge pump seal which needs to be replaced. However I will state again, tighten the various bolts in the leaking area to include the valve covers, upper an lower, clean the area well, and then as you have done.. crank the car and re-check for the leak. There are several things in that area if leaking can provide the dribble of oil.

The scavenge pump has a line running to each side, check to see if they are tight

Also see this link.. it show the seal that would be leaking; Scavenge Pump

And here is a pic of the back side of the pump showing the lines and the housing that holds the seal..

LucaScali · 07-16-2015, 09:10 PM

Thanks, onboost, but whatever may be leaking from the valve covers isn't the problem right now (I actually did tighten the bolts as you suggested previously). The oil causing the smoke is clearly coming from the scavenge pump and only once the engine is turned on. It's not subtle. Thanks for the link and the pic. I'm going to check the lines first and then figure out how to replace the scavenge pump seal. Hopefully that will do the trick or I'll be back here again.

Incidentally, I'm also in the DC area. Appreciate all your responses and thanks for bearing with me.