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JohnJL JohnJL is offline
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Join Date: Jan 2005
Location: Toronto, Ontario
Posts: 4,729
Overflow oil tank is puffing smoke

I am trying to diagnose and deal with a problem thats always been there but has gotten noticably worse recently. The motor has a season on it, and wasnt stessed hard, there no reason it should be acting differently so I wonder if I just didnt notice it so bad before or if anything has changed.

The motor is a 3.2l supercharged running ~12psi or .9 bar.

I have a 2+ litre overflow tank plumbed off the oil filler neck. It has a filter on the top, and it drains to the 4-5-6 upper valve cover. It does not fill up with oil, but it does puff smoke out the filter with each cylinder firing. I took the filter off the overflow tank vent and see it clearly puff. If I block that filter hole and open the oil filler neck, it puffs out there with each cylinder firing.

The smoke is prolofic. I need to do some better sealing of the firewall to the cabin, so I get lots of smoke in the cabin now, particularly shortly after I come off full throttle and get back into it after a corner. Even when the cabin is fully sealed, I cant have that smoke coming off the back. The filter on the overflow tank tends to cool/collect the oil vapor and it drips down in the engine compartment and on the headers. Very stinky and smokey.

Firstly, I am not sure why this is happening and if it indicates a problem. Right now I have the normal oil line coming off the oil filler neck to the engine case. I also have that same filler neck venting to the overflow tank, which is the one smoking like crazy. Should I be plumbing this differently?

I scanned a couple of alternatives, not sure if these would help. Both are variations on feeding that smoking bent back into the intake. The obvious downside being I would now be feeding my engine intake with oil vapor which cant be great.

Anyone help with diagnosis of whats happening, why, and what I should do?

If I do plumb it into the intake, seems it would need to feed in before the throttle body, right? Option 2 below would seem to bleed an unlimited leak after the throttle body, which would essentially be a major intake leak.


2007 911 Turbo - Not a toy
1985 911 Cab - Wife's toy
1982 911 3.2 Indiash Rot Track Supercharged track toy
1978 911 3.0 Lichtbau toy "Gretchen"
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Old 05-12-2013, 04:59 PM
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