Engine smoking...then fine...whassup?

[BillyIdaho]

Well, my new project 911 is baffling me.

Sunday I did a little work on it, started it up and it smoked a little. The car has basically been sitting for 4 years, apart from being started a few times for prospective buyers by the gent selling it, and when I drove it the two miles home. I expected a little smoke.
Anyway, after warming it up, I take it for a little joy ride up the street - no front fenders, sunroof, hood, doors, decklid, seats - basically your typical Porsche turning a lot of heads. Beautiful cars, y'know...

While I am driving it, it begins to SMOKE like the Jed Clampet special, and drip oil out the tailpipe. I park the car, fearing the worst. I posted a question here about the engine serial #'s, and asked about a MM rebuild. (Since researched here and discarded as a Pandora's box- thanks!)

Tonight, I start the car - no smoke. I let it idle - still no smoke.
I give it a few gentle revs, no smoke, and then while it runs about 10 minutes - no smoke and no oil drips out the pipe. Seems to be running really nice. Neighbor even came over and commented on how nice it sounded, and at the odd lack of smoke.

Is it posibble the motor just needed to get a ring unstuck or soak some dried out gaskets/seals in oil that were allowing oil into the combustion chamber?

I plan on having someone qualifed look at the motor to get a real opinion on what it needs once I have the car painted and back together, of course.

Anyway, ordering the "101" book right now, and I look forward to becoming a regular here. Seem like a pretty cool group.

Regards,

[Early_S_Man]

Billy,

If oil was dripping out the exhaust, while it was smoking before ... it may have been just oil in the muffler that was burning off!

I suggest that you adjust your valves, then run it some more, and after it is fully warmed up ... do a compression test. That will give you a good idea of the engine's general condition.

[A Quiet Boom]

When I bought my current car from my brother it hadn't been driven for something like 3 years, the engine smoked horribly for the first two days until the rings resealed. I used to have the same problem every spring with my drag car although it generally reseats the rings in the first hour or so. I'd follow Warren's suggestions first before you get too worried. It's also very possible that being a flat engine oil seeped past the rings into the exhaust and didn't burn until you got the motor hot enough. I had a neighbor with an old VW based dunebuggy that he parked sidehill next to his garage over the winter, every spring I swore the engine had to be shot but after his first outing it would be fine. To solve the problem (and danger of burning oil in the exhaust) he started removing the headers and putting duct tape over the ports before winter storage. Like Warren said the compression test will tell a lot.

[Wayne 962]

YES! 911 Engines are notorious for this. After sitting for long periods of time they will smoke and run horribly. After about 200-300 miles, they will run like new (if they are okay to begin with). This is one reason sitting engines will show bad leakdown numbers, only to have them come back on-line as good as new after a few hundred miles.

-Wayne

[Early_S_Man]

Billy,

Just for clarification ... oil smoke on startup isn't necessarily being burnt in the combustion chamber! Lots of people speculate about oil seepage past the rings, etc. ... causing the oil smoke, but I have examined spark plugs on several 'smokey startup' engines and found no trace of oil on the spark plugs!

Many 911 engines smoke on startup and never any other time! The average owner always gets concerned without trying to find out what is happeneing. I have seen engines that smoke occasionally, and others that do it every time, yet never show a sign of oil on the plugs! After much reading on the subject and examination of engine details ... have come to the conclusion that as the oil level in the sump rises above the level of the exhaust valve guides ... oil is actually seeping 'up' the exhaust valve guides and running down the exhaust port into the heat exchangers! The reason this can happen is that the white Teflon valve stem seals that allow a 'controlled' amount of oil seapage in operation to keep the valve stems lubricated ... are not good at resisting static pressure from a rising oil level in the sump! It seems to be worse when the car is parked on an incline, and I suspect that the higher oil level at cylinders #1 & #4, or #3 & #6 when inclined raised the static oil pressure at the valve stem seal ... and leakage is worse than if parked on a level surface!

Naturally, if an engine sits for weeks, months or years ... a considerable amount of oil can be in the heat exchangers and muffler! It could take an hour or more of running at highway speeds to burn the oil off!

A past Pelican thread by a frantic owner with a badly smoking engine ... turned out to be a used muffler that had been purchased and recently installed! The troubleshooting took multiple days, but no oil on the spark plugs, and no oil in the heat exchanger outlets ruled out the engine as the source of the smoke! So, the used muffler became the culprit!!!

[911boost]

Warren,

While I did not start this thread, I appreciate your reply. I am thinking that it answers a question I was going to post on here. After driving my Carerra for long periods and then parking it for a couple of days, I sometimes get smoke at start up. It last only about 15 seconds but is noticable. It doesn't do this all of the time, just occasionally.

I have no drips, the engine is very clean and it does not use a significant amount of oil.

Bill

[stevef]

This is a great topic and close to my heart. I completed a top end rebuild on my 2.0L last winter. When I got it going again it smoked. I knew I might get some smoking as the oil used in the rebuild process worked it's way through the system, I also expected to get some oil burn as the rings reseated but I never expected the amount of smoke from the heat exchangers. I bought the car as a non runner so I had no previous running experience with it. I was devastated to start with to think I spent the winter working on it to find I screwed up. My neighbour who had worked in Germany in the 70's and 80's in the military and had had several P cars while there helped me get through it,as did this board... my local support system!
Happy to say everything is working great.

[Rich911E]

I did the same thing. When my 2.4 pulled a head stud, I bought a 2.0T motor from a guy in Huntington Beach to use while I fixed the 2.4. It didn't cost much and seemed pretty clean inside (once I got all of the goo off the outside), so I just stuck it in and ran it. It smoked like James Bond's DB5 for a the first 20 minutes, but now that it has cleared up, it is still running like a champ.

A friend (KeithO64) did this with a 2.2 liter lately and had the same experience. Smoked like crazy until it burned off the oil in the exhaust and now it is clean and runs strong. These little old motors are pretty indestructible.

What we did on both motors was start them with about 70% oil and 30% ATF. ATF has a very high detergent content and solubilizes all of the old oil from the inside of the engine. After about 2-3 hours of operation, you drain it out and put in regular oil. As you might imagine, the oil/ATF was pretty nasty, but since then the oil has stayed nice and clean.

Rich

I have been using the oil formulated for older engines (which is supposed to easy on older style gaskets) and it seems to work well with this 1969 2.0 engine. There has been less seepage than with Mobil 1.

[stevef]

Rich, I like the analogy to 007, My wife told me she thought I was trying to emulate a World War II destroyer laying a smoke screen.
I had already loaded Mobil 1 in my motor before I learned from the discussion on this board about old style gaskets etc. I guess I should put dino in on my next change. Although I don't seem to be having any problems I assume I could

[justin]

Hmm, I just got my (new to me) 76' 930 running today and it smoked like a train,very badly. I realized that the previous owner had over filled the tank about 2 quarts of oil,will that cause it to smoke? Also oil is dripping out of the exhaust too. The car sat for about 2 yrs before I got it. Sounds like oil dripping in the heat exchangers? The motor has been recently rebuilt by a shop I am pretty familiar with. I'm new to the 911 car. So any help would be appreciated.
Thanks

[Chuck Moreland]

The oil can get into the exchangers/muffler. I once had a car leaning steeply with one side high on jack stands for 2-3 weeks.

Some oil actually spilled out leaving a puddle, though I'm not sure where it leaked from. When I started the car it soon began to smoke like Cheech and Chong. It went on for a long time, maybe 30 minutes. Obviously it wasn't oil in the cylinders burning for that long.

Then it cleared up and all was back to normal.