Oil and smoke (lots) out exhaust suddenly 3.6L

[356graham]

Looking to validate and get some suggestions on what are the logical next steps. Here are the facts (some may be irrelevant, but facts none the less) and a couple pictures.

1972 911E with a 3.6L 993 transplant engine. This car is very new to me, and I don’t know much about its history.



Prior to “the incident,” there was some oil smoke – mostly on start-up – but within acceptable visible limits. I haven’t had the car long enough to know what the oil consumption is.

“The incident” occurred driving home from work on the freeway in the hard rain, and driving quite conservatively. After about 1 mile of driving, something occurred suddenly that caused the car to start running a little rough. I attributed this to the wetness and possible wet intake filter, but when the traffic came to a stop, I was enveloped in a cloud of smoke – mine. For the remainder of the drive, the car smoked on acceleration, on deceleration and at idle. I got the car home and said a prayer for my wallet.

A couple days later – after mustering the courage – I moved the car over to my workshop bay of the garage. I had to start the car to move it and noticed;
- No (or very little) smoke on startup – a good sign I thought.
- Idle good – no signs of rough running.
- After about 30 to 60 seconds, oil started to be blown out the little holes in the exhaust and the smoke started again. Enough to get a double take from the neighbor who was walking her dog past the house.
I shut the car down. I pulled all of the lower plugs looking for evidence of oil, but they looked really clean. Wish I had taken pictures. Now for the Q&A.




Q: am I sure it’s oil coming out and not gas or water. (I can answer this one myself)
A: yes. Short of doing a taste test, I have validated it *IS* oil.

Q: is oil overfilled (I can answer this one too).
A: No. I hadn’t added any oil – level was good, pressure was good. Still is.

Q; Does the fact that the lower plugs were not fouled in any way at all eliminate the chance of ring(s) failure or hole in a piston or inadequate case ventilation?
If so, then I’m thinking sudden massive valve guide / seal failure allowing oil into the exhaust ports and not into the combustion chamber.

Q: Do valve guides and/or seals fail this way? I thought that they wore over time.
I’ve read on this board mixed opinions regarding the ability to detect worn guides by wiggling the valve stem back and forth – both when the valve is seated and also when lifted slightly. Regardless, it’s pretty easy to remove the valve cover and give this a try.

Q; What else would you check while the engine is in place and running?

Q: Would you be concerned about running this engine while diagnosing?

I’ve got a feeling that I’ll be pulling this engine and working the top end, but I’m looking for some validation before I start down that road.

Thanks in advance for your assistance.

[Wil Ferch]

Quote... " Q: is oil overfilled (I can answer this one too).
A: No. I hadn’t added any oil – level was good, pressure was good. Still is.

Describe in detail how oil was checked...

1.) car on level ground?.....
2,) engine running and running at idle speed, 800-900 RPM, (+/-) ? .....
3.) engine up to operating temp...about 194 degF...about 8 o'clock on temp gauge?......
4.) To what level was it filled...top or middle or near "add" line?.

[johnsjmc]

Here is a longshot. Other than an overfill. I notice from your picture the crankcase vent hose appears to be a rubber heater type hose. When it gets warm while running, this type of hose gets soft and can kink ,because of the path it is formed into. Oil fumes also soften this type of hose . If this has happened there is a chance that increased crankcase pressure will force oil past rings and guides into the engine to be burned. When it cools the hose is harder again and may not choke off the crankcase ventilation.

[Bob Kontak]

johnsjmc - I like the theory. The breather hose does not look unique though, to a 1972.

What did you have on your SC/3.6 transplant that would resist the kinking?

Maybe the "incident" could have been the hose collapsing and when he started it recently it was just oil smoking. Jeff - did it run rough on your recent start?

[johnsjmc]

I ended up using off the shelf heater hose and had the kinking issue until I carefully trimmed the length to keep the hose close to straight. I have since sold the car and have not heard of any problems from the new owner . The OEM hose is the fabric wrapped stuff which is oil resistant and stiff but I didn,t find a source when I did my install. I never had an oil smoke situation (other than at start up after prolonged storage) as described above but think it is a possible explanation for this sudden oil smoking.

[356graham]

To address a couple of the suggestions;
Oil level measured properly and at 4/5 down from the "max" position on the stick - meaning 1/5 up from the min position. I'll try an ascii representation;

max
|
|
|
|< here
|
min

On the vent hose, I don't see any visible kinks or collapsed areas. It appears really good around the front of the engine and bends nicely.

Running fine - I started it again. No smoke on start - 50 seconds it starts smoking and get's progressively worse.

Now, here's an interesting side note that is sending me down a different path.

I'm eating dinner in the garage now and just used the same paper towel that I used to clean up the oil weaps from the exhaust to wipe my mouth (I know - not best practices). It smells like gas!

I think there is some amount of raw gas in my oil - and I'm definitely questioning my first assumption.

So, I just wiped the dip stick a couple of times with another paper towel and - again - a gas smell. Looks like oil, feels like oil, but I'm pretty certain there is gas the oil system.

Obvious next step is to change the oil ASAP. But how did gas get in the oil? Especially while driving down the freeway?

The wiring is a nightmare and I can imagine that some moisture - or a lot of moisture like the rain we were having - would wreak havoc on the DME - possibly telling it to dump fuel into the cylinders.

Or, maybe this supports a broken ring(s) / theory where any fuel put into that cylinder gets squeezed into the case on the compression stroke.

[johnsjmc]

If you are dealing with a rich running engine and excessive fuel diluting the oil. I would consider the cylinder head sensor suspect. The CHT acts like a choke and richens the mixture for starting. When I had one fail the engine was difficult to start when hot but did start and ran very rich. You could smell it in the exhaust. There is a chart of resistance measurments at diff temps somewhere.
The O2 sensor doesn,t trim the fuel mixtures until the engine is warmed up , until that point it runs in open loop with input from the CHT. then both cht and o2

[356graham]

Measured CHT at 1423 Ohms on the now luke-warm engine. According to the tech article on CHT replacement (Pelican Technical Article: Cylinder Head Temperature Sensor - Upgrade for 84-89 Carrera) that is within the 1K-2K ohm range.

Thanks for all the help.

[356graham]

Oh, and I'll check it again in the morning with the engine stone cold.

[HARVEYWEIDMAN]

Jeff,
I had one act similar once when I soaked the air filter with water. It caused a over rich mixture. Might be worth a try since you were in the rain..
H

[356graham]

Harvey, I hope that it is something relatively simple like that. So, what was the resolution to your problem? Dry out the intake filter, change the oil and then?

Thanks.

[WERK I]

Originally Posted by 356graham

Looking to validate and get some suggestions on what are the logical next steps. Here are the facts (some may be irrelevant, but facts none the less) and a couple pictures.

1972 911E with a 3.6L 993 transplant engine. This car is very new to me, and I don’t know much about its history.

...................snipped for space ...........................

I see it is a '72 911 and you say the oil smells like gas. Someone put gas in the oil filler tank? (right rear passenger side filler door)
I know its a remote chance, but stranger things have happened.

[356graham]

Hi Dave,

The '72 style oil tank is no longer there - removed in the conversion.

I'm pretty sure that the fuel got into the oil by way of a very overly rich condition.

And to follow up on the CHT, it now reads 2.85K cold which is right on spec.

Thanks.

[WERK I]

Hi Jeff,
Have you ruled out the possibility that oil may be weeping form somewhere on the engine onto the exhaust manifolds? You'll really get a lot of smoke under this condition as well.

[johnsjmc]

Your CHT is working but I think it is out of range. If 1-2 K ohms cold is normal. Then 2.85 seems like it will be causing rich running on a cold start. San Diego is never sub zero outside is it?

[Staylo]

Save yourself the stress and trouble and do a leak down test.

[johnsjmc]

Leak down test. Why didn,t I think of that . Agreed.

[ischmitz]

I'd be curious about the leak-down too. Do you have any reliable history on the engine other than the ususal "less than 20k miles on this perfect donor...." kind of BS?

What happens when you open the oil filler cap while the engine is idling. Do you get a distinct change in the idle note. If not something may be wrong with you breather setup.

Ingo

[356graham]

johnsjmc - you are right 2850 ohms is outside the 1k-2k range I stated in previous post. I've since read several other posts that discuss over 2300 ohm at cold being OK.

Leak down - I'd like to be able to do this myself anyhow so I'm going to invest in the right tool for it. I've done a little reading and found the Harbor Freight tool is junk - will have to spend real money for this.

Ingo - interesting point on the breather and something that I've been curious about. In the first picture you will see that the oil tank has a vent pipe and filter open to ambient air. So, it isn't a sealed system at all - therefore no change in idle when the filler cap is removed.

My previous 911SC (stock) and '72 911T (stock) prior to this one were sealed and definitely noticed a rough idle when the oil cap was removed.

This set-up (remember - not stock at all 3.6L transplant in a '72) *does* work. It was working up 'till a couple days ago. But I can't understand how a vented system can provide any positive ventilation.

[ischmitz]

Oh, I missed the little air filter. So you just have the crank case breather hooked up to one of the oil tank lines and the other vented to ambient. On the plus side you'll never ingest oil when you overfill the oil tank. I assume the intake port that normally connects to the other port of the oil tank is simply blocked.

Is there anything else on the intake trakt that is connected to the oil tank/breather circuitry? Else. I really don't know where the oil is coming from.