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Weird traces of smoke coming from around the downpipe. I have no idea where to start


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For some reason when I drive my car for more than about 15 minutes (so once the car is fully warmed up) a small amount of smoke starts appearing from around the intake manifold area. Its very hard to pinpoint the exact location because it is a VERY small amount of almost invisible smoke. In fact the only reason I notice it is because you can smell it inside the cabin after a few minutes.

I looked for some clues as to what could be burning and I found some grey-ish residue right underneath the intake....

 

The only thing I can think of it being would be some kind of coolant leak dripping onto something hot... Other than that I have NO idea where to even start diagnosing/fixing this other than taking the car into the shop, which I really dont want to do.

 

Any suggestions?

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I had torn CV and a leaky VC. It was the VC that was making most of the smoke. But it was not what I would call a "trace" of smoke. more like a chimney. Pretty easy to visual inspect for both.
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I had torn CV and a leaky VC. It was the VC that was making most of the smoke. But it was not what I would call a "trace" of smoke. more like a chimney. Pretty easy to visual inspect for both.

I'm leaning towards a leaky VC... how would I search for this? Is it something I can just do myself?

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VC gasket is a possibility either way you are gonna have to get under the car. So check for both grease on the DP and traces of oil at the mating seam of the VC and block, also have you noticed any oil spots on the ground where you park? I am still inclined to say it is the CV slinging grease as I had same issue and it resulted in slight smoke ie high temp grease won't burn off as readily where as oil burning off will be a thicker smoke.
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VC gasket can be done yourself. Not difficult to do just to get to the bolts especially on the turbo side...a lot more in the way...you may need to remove motor mount bolts to manipulate the engine and get a little more space to work...

 

I recommend you source a new oem gasket and ultra grey RTV to reaffirm the seal. It will need to sit or 24hrs (I believe) in order for the RTV to cure before heat should be added to the equation. Make sure you torque these bolts to spec as well. The manual even recommends a certain pattern. Also, make sure nothing gets inside heads...

 

Before you make any assumptions about the issue you should check for a slow leak at the mating surface where the valve cover meets the heads...it could also be the turbo oil drain tube (more common if turbo has been replaced) and I would also inspect the CV boot to be sure before you tear into it...

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VC gasket is a possibility either way you are gonna have to get under the car. So check for both grease on the DP and traces of oil at the mating seam of the VC and block, also have you noticed any oil spots on the ground where you park? I am still inclined to say it is the CV slinging grease as I had same issue and it resulted in slight smoke ie high temp grease won't burn off as readily where as oil burning off will be a thicker smoke.

 

Ok I just checked my CV joint. Pretty sure you were right about it. I didn't raise up the car so I couldn't get too good of a look at it but I'm fairly certain the interior boot is torn. Also, there is a good amount of dark grease coating both the downpipe and also around the boot itself.

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Bingo!! Super easy fix man! Takes a little time but a boot and grease kit from Subaru is like $20-25. They also reuse the clips on the boot. It'll take a few hours your first time but its not super complicated. Just remember the order it came apart. :)
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