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Join Date: May 2004
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Smoking like a chimney after shutdown

My engine smokes like a chimney after I shut it off. I spent a good part of the weekend looking for an oil leak, but didnít find any. I even took off the CIS unit and shroud to check the breather cover and oil temperature unit, but no leaks! There are also no obvious leaks on top of the engine, or in the engine bay. I jacked the car up and couldnít find any leaks under the car either (except minor valve cover leaks which I fixed).

I recently completed an rebuild and got it running reliably a few weeks ago, after replacing the fuel distributor and WUR with used ones. The car runs great now, but still smokes after I shut it off. My wife is worried that Iíll burn the house down. Is there any chance that itís the excess silicone and gasket maker stuff burning off (itís a lot of smoke, but only after I shut the car off)? Any other ideas? I already drained and refilled the oil to make sure it wasnít overflowing into the air box. I was also used a funnel to avoid the breather hose connection. The car is a 1974 911.
Old 03-13-2005, 04:01 PM
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When you had the car jacked up, did you run your fingers along the tops of the heat exchangers? (I'm assuming you have HEs and not headers or thermal reactors.) If you are geting any oil leaking there, there can be a huge smoke problem on shutdown.

If this is happening, when it's running, the air being forced down through the cylinder cooling fins and onto the HEs by the fan can mask it, and then when you shut it down, any oil on the top of the exchangers will burn off, causing smoke.
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Last edited by cowtown; 03-13-2005 at 04:23 PM..
Old 03-13-2005, 04:16 PM
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Did you check behind the alternator? Any smoking from that location would be blown under when fan is spinning(I think); anyway, it seems 2 of my thru case bolts are leaking, which I could not find until I removed my fried alt.
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Old 03-13-2005, 04:16 PM
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The most likely suspect is oil on the exhaust. When in motion, or even with just the cooling fan running, smoke can be dissapated to the extent that it is not noticed. Upon shutdown, it just rises with the heat.

Oil can work its way to the exhaust from many sources and usually does. I have a leak that I'm still chasing. My next trick is to clean the engine one more time and lighty dust it with some flour. I'll run it a few minutes and find the source. Right now, it looks to be coming out of the back (front, if you prefer, the part I can't see) of the MFI pump.

Of course, that wouldn't be your problem, but leaks up in that region are hard to see, even more so on a CIS motor.
Old 03-13-2005, 04:21 PM
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Thanks for the explanations. It seems obvious now, but I didnít think of it before - that the smoke only rises up through the engine compartment after the fan stops pushing the air. To fix the leak, it sounds like I need to take more time looking under the car. Again, after taking the CIS unit and shroud off, I didnít see any signs of leaks on top of the engine. Maybe Iíll try the baby powder or flour trick.

Charley
Old 03-13-2005, 04:52 PM
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Is there another possibility?

After work yesterday, I jacked up the car and again searched for signs of leaks Ė nothing. There is only a few hundred miles on the engine since it was completely rebuild. I used plenty of gasket sealer on the case. I had the machine shop assemble the heads and they used globs of some kind of silicone stuff. Is it possible that this is whatís causing the smoke???

Charley
Old 03-17-2005, 04:09 PM
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Have you let it run and looked around to try and see where it's coming from...be careful of the fan though.
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Old 03-17-2005, 04:28 PM
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Last weekend I let it run for awhile and then checked for leaks. The only thing I found was a small leak on the valve covers, which I fixed. After cleaning the area, it still smokes. The only thing left undone is the flour treatment. However, since there is no apparent oil present, I can't see what's generating all the smoke.
Old 03-17-2005, 04:33 PM
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Some sources

1) overhead cam lines
2) Valve covers (which you know about)
3) oil thermostat
4) possibly the switch behind the air filter

Ask me how I know.
Old 03-17-2005, 05:47 PM
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Thanks for the list.

Iíve checked everything except for the switch behind the air filter. Can you see it from the rear of the car, or do I have to do a partial engine drop?
Old 03-17-2005, 06:29 PM
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Quote:
Originally posted by Charley
Thanks for the list.

Iíve checked everything except for the switch behind the air filter. Can you see it from the rear of the car, or do I have to do a partial engine drop?
My understanding is that a partial engine drop is required to reach it. You can probably check it by using an extension mirror. I'm sure others here know for certain.
Old 03-17-2005, 07:58 PM
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I've heard of catalytic converter getting so cherry hot from a missfire/etc. that they've caught carpets and dry grassy fields on fire...
I used to have a smoke stack after shutoff, and fixed the leak from the oil thermostat(center of the case hidden behind the CIS and difficult to get to) which was dripping onto the heat exchangers.
The crank seal and cooler are next and obvious.
Old 03-17-2005, 08:37 PM
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Charley,

The oil pressure light switch is right next to the thermostat to the right of the breather hose connection, and more foward. If it appears that this is leaking, don't tighten it too much as they will break; order a new one, it will come with a new seal(not expensive IIRC). Also, have you checked your drain line from the airbox?
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Old 03-18-2005, 05:37 AM
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I did replace the oil pressure sender (next to breather hose connection) and it was dry when I checked it last weekend. I don't have the drain line from the airbox capped, just a hose that exits the engine compartment. Could that be it? I thought if my oil was not overfilled, nothing would drain?
Old 03-18-2005, 02:01 PM
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I don't know for sure, I did not have a hose at all so I figured I'd mention it.
If it makes you feel better I still haven't found mine. Some kid in another car a few months ago screamed " mom, that car's on fire!!" at a light, kinda embarassing.
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Old 03-18-2005, 03:09 PM
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Quote:
Originally posted by Charley
...There is only a few hundred miles on the engine since it was completely rebuild....
Charley
My car had the 'shutdown' smoke for at least 500 miles. Not until I took it on a highway road trip did it get better. My heat exchangers have a few pin-holes on the top. When I did a valve adjustment, the oil dripped into these. It seemed to stay there forever. If it's not "call the fire dept, that guy's car is on fire" bad, keep an eye on any potential leaks, and get it out on the highway and work it hard.
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Old 03-18-2005, 06:59 PM
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Jay,

Thanks for the advice. I know that oil got in the heat exchangers from a valve adjustment and from my first oil change. I'll work it on the road for a while.

Charley
Old 03-18-2005, 07:28 PM
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