Smoke from engine compartment?

[djb3]

Hey guys, this is my first time posting to the 911 technical forum. I have been watching the activity here for some time, ever since I picked up my first Porsche. It’s a 1976 stock 911S (I know, I’ll post some pictures once I get it all cleaned up). I found this car on Craigslist for what I thought was a really good price, but have since learned the mark down was probably because it had a Motormeister rebuild (I know, I should have checked here first, and ultimately passed on the car). In any case, the engine works fine, haven’t had any major issues just yet, just a few oil leaks. It also gives me something to learn on and makes a good starter Porsche.

So, I decided to tackle some of the oil leaks and replace to soft lines leading from the oil tank to the engine. While I was at it I decided I would check the valve clearances, since it looked like the PO hadn’t done that since the rebuild in 2002 (about 5,000 miles ago). To my surprise most looked to be just right. Then I filled the oil tank back up with 9 quarts of Swepco 306 15W-40, started her up and drove off. Everything seemed ok, a little rough in the beginning, but then settled into a nice idle. Then I noticed the smoke, pulled her back into the garage and shut her off.

It appears to me that the black box mounted on the passenger side engine compartment wall, just behind the oil tank filler stack was smokeing. Not just a little, but a lot, enough to fill up the garge so I had to open all the doors and windows. I didn’t notice any fire, and everything warm to the touch, not hot. Any ideas why this might have happened? What is that black box? Is it unusual? Normal? Etc.

Any input is greatly appreciated, Thanks, Dave

[KNS]

From the description it sounds like your charcoal canister - don't know why that would smoke though...

[zippy_gg]

What did the smoke smell like? Electrical? Oil? Plastic?
These could be clues as to what the problem is.

[ossiblue]

My first thought was oil tank overfill but you say the smoke is not coming from the exhaust--it's coming from the "black box". I agree with Kurt that the box in question in the charcoal canister.

There needs to be some more information. First, there should be hoses connected to both ends of the canister, and if there are, how can the smoke be coming out is such large amounts? I suspect that at least one end may not connected.

Second, if the smoke is from burning oil, it could be from oil leaking from somewhere under the shroud and burning from the hot engine. Then, the smoke is pushed into the charcoal canister by the alternator fan as that is where the air to evacuate the canister comes from. Try removing the hoses from the canister (if they are all connected), start the car and drive it warm, and see if smoke is coming from a disconnected hose. (No damage by doing this as these hoses are for the gas tank emissions.)

[RWebb]

is this black box oval in Xsection? that is the canister

I would also have assumed oil fumes, but... pull the offending out and examine it

[djb3]

Hi guys, I still need a little help. Any and all thoughts are appreciated.

As suggested above, I pulled the charcoal canister out, and ran the car around the block to get the smoke going again. Pulled the car into the garage, and checked the hoses that had previously been feeding the canister for smoke, and there was nothing. So, my first diagnosis of the source being the canister was wrong. However, there was still a ton of smoke coming from the corner of engine bay where the canister was located.

I did some more searches here on Pelican, and decided that I must have a leak with one of the following three items: oil pres switch, thermostat, or breather hose. I ordered the parts from Pelican, pulled the CSI off the engine (yes, this was hard to do with the engine still in the car, but I eventually got everything out, and only had to cut one hose in the process).

However, to my surprise, all three suspects, the oil pres switch, thermostat, and breather hose were all dry! Is it possible for the oil to have burned off without leaving a mark? The smoke is new, and only experienced in two short 2 mile drives around the block, but it was a lot of smoke. Looked like the engine was on fire.

There are a few other items I noticed but didn’t mention above:

1) When I drove the car around the block the second time, I downshifted from 3 to 2, and I got a ton of smoke in the passenger compartment through the heating system.

2) After the second drive, I crawled under the car, near the rear passenger side wheel, and I thought I noticed smoke coming out of the fresh air mixer for the passenger heating ventilation (but, maybe my eye’s were playing tricks on me).

3) There was oil on the under side of the passenger side SSI, but not the drivers side.

4) It doesn’t leak when parked in the garage, just one or two drips, which I believe are residual oil drips from the source leak while driving it.

5) Also (this maybe unrelated) there was some oil on the underside of the air box above Cylinder 6 (passenger side front). Also the outside of the fuel injector and fuel hoses for cylinder 5 and 6 were coated in dry oil.

Any insight would be greatly appreciated. Thanks.

[PorscheGAL]

Check the the topside of the SSI under the passenger side valve cover for dried oil. When mine leaks oil, even a little, it drops on the back of the SSI and causes it to smoke. I'm amazed at how much smoke is generated from such a small leak.

Further, my experience is when driving the air flow under the car blows the oil and it misses the SSI. When I stop for a while, it will drop on the hot SSI and start to smoke.

[James Brown]

Try this at home (wife will love this) heat a pan on the stove to 450˚ and place 2 drops of swepco oil in the hot pan. See how much smoke it produces! A small amount of oil can make a lot of smoke and not drip on the ground, check the oil return tubes and the lower valve cover on the passenger side.

[Scott R]

Guarantee this is coming off the exchanger like mentioned above, the only question is where from? Probably not the answer you want but I would have dropped the engine to do all of this. Between the valve adjust and the CIS removal and the oil seals you could have probably saved some time. Also would be easier to find.

[azasadny]

Yep, just a small amount of oil leaking onto the heat exchangers will cause a lot of smoke. If you open the defroster, do you get an oily film on the inside of the windshield?