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2004 330Ci 85k miles
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Discussion Starter #1 (Edited)
There are so many requests for solving problems that usually start with "do a smoke test for vacuum leaks" that there's a real need to have a single thread dedicated to smoke testing. Then we can just post the link to this thread when someone needs smoke testing info. Please chime in with your tips, links, experience, etc., and I'll curate it all in this first post. I'd like to dedicate this thread to jfoj for posting most of this information in various threads over the years. I plagiarized his posts heavily. :bow:

Homemade Smoke Tester
Other Smoke Testers
Tricks to Doing it Well
  • start with a fully cold engine, some leaks go away with heat expansion of parts
  • put the front end up on jack stands so you can get under it while looking for smoke
  • remove all engine covers (top and bottom), air box, and anything else blocking good visibility all around the intake manifold (power steering reservoir, cabin microfilter tray, etc.)
  • use a mechanics mirror and bright light to search for smoke
  • open the oil filler cap while you pump lots of thick smoke into the intake until smoke is coming out the hole then replace it, that ensures smoke has filled the crankcase, keep pumping while you search for smoke leaks
  • remove the one-way valve from the brake booster grommet, plug it well, then see if the STFTs go down
Guides
Common Leaks
  1. Upper and lower intake boots
  2. Upper intake boot around F connector
  3. DISA main O-ring and shaft area
  4. Vacuum hoses and plugs at the rear of the intake
  5. Fuel pressure vent hose that connects to the F connector on the upper intake boot and under the drivers floor board where it connects to the fuel pressure regulator
  6. CCV and hoses, especially the lower oil return line
  7. Dipstick and dipstick guide tube
  8. Oil fill cap
  9. Valve cover gaskets and cracked valve covers
  10. SAP vacuum line to Kombi valve on front of engine, this will not leak smoke because of the control valve under the rear of the intake
  11. Power brake booster, sucking jet pump, and related hoses
Note that the brake booster usually cannot be smoke tested because of the input vacuum check valve at the booster connection.

Smoke Test Videos

https://youtu.be/AsgB9eBl58I

https://youtu.be/1sRZ5ves1DM

https://youtu.be/qGcOepRgU6c

https://youtu.be/Np_duzsaZxI

https://youtu.be/3encrkBsss0

https://youtu.be/dfAkpEExnQc

https://youtu.be/zMok2y05jNE

How to Make a Smoke Machine

https://youtu.be/EhNQiIRsCCk
 

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I used homemade and then cheap smoke generators. Then I bought a Stinger Pro. only a few $ more than cheap machines, and much more reliable and easier to use. Well worth a few extra $ for the reliable tool.
 

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Here to serve y’all
2004 330Ci 85k miles
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Discussion Starter #4
I used homemade and then cheap smoke generators. Then I bought a Stinger Pro. only a few $ more than cheap machines, and much more reliable and easier to use. Well worth a few extra $ for the reliable tool.
Thanks! Added a link to the Stinger 2 as well as smoke testers on amazon and ebay.
 

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'02 330i 5-Speed
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I used homemade and then cheap smoke generators. Then I bought a Stinger Pro. only a few $ more than cheap machines, and much more reliable and easier to use. Well worth a few extra $ for the reliable tool.
^This. I bought the cheaper Stinger model when the company offered it (they don't anymore I believe). Still one of the best tool purchases I've made:



Here's one of my smoke tests:

https://www.youtube.com/watch?v=qGcOepRgU6c



Here's a question I have that maybe you could put the info for in the top post: What diameter PVC cap should I buy to make a homemade plug for the upper intake boot? In the above test, I use a long funnel that I tape into place, but as you can see, it's not a perfect seal. Would be great to have a PVC cap or similar with a tapped fitting in the center; that way I can just use the boot's hose clamp and get a better seal.

I could just remove the MAF sensor and take it down to Home Depot to match it up, but if anyone has that info handy, it would save some hassle. Thanks!
 

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I just put a latex glove over the maf and insert the tubing through a hole in one of the fingers.
 

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I just put a latex glove over the maf and insert the tubing through a hole in one of the fingers.
You don't want to be blowing smoke through your MAF. It will sh1t up the sensor wire. The glove thing will work just as well with the MAF removed.
 

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balidawg, i haven't seen whole video (just a fraction of the 1st), nor read the thread yet, but i liked your smoke machine, so simple, and looks so easy to use.
 

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2004 325i automagic
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Here's a question I have that maybe you could put the info for in the top post: What diameter PVC cap should I buy to make a homemade plug for the upper intake boot? In the above test, I use a long funnel that I tape into place, but as you can see, it's not a perfect seal. Would be great to have a PVC cap or similar with a tapped fitting in the center; that way I can just use the boot's hose clamp and get a better seal.

I could just remove the MAF sensor and take it down to Home Depot to match it up, but if anyone has that info handy, it would save some hassle. Thanks!
Wouldn't it be better to take the intake boot with you to Home Depot, so to speak? Since that is what the pvc adapter will plug into to run the smoke test.

Edit: Maybe it doesn't really matter. I've thought about this as well. If a pvc pipe itself happens to fit in the intake boot, then that could also work if cut very short (like 2 inches) and then the corresponding end cap fitted over the end.
 

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'02 330i 5-Speed
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Wouldn't it be better to take the intake boot with you to Home Depot, so to speak? Since that is what the pvc adapter will plug into to run the smoke test.

Edit: Maybe it doesn't really matter. I've thought about this as well. If a pvc pipe itself happens to fit in the intake boot, then that could also work if cut very short (like 2 inches) and then the corresponding end cap fitted over the end.
Maybe. It's just more convenient to take the MAF sensor than to remove the intake boot. I guess I could just measure the darn thing. :idea:
 

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Here to serve y’all
2004 330Ci 85k miles
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Discussion Starter #11
I just put a latex glove over the maf and insert the tubing through a hole in one of the fingers.
Yeah, this is what most people do. Because a latex glove can easily stretch and fit over various sized ports and the finger is perfect for connecting the smoke machine hose.
 

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Here to serve y’all
2004 330Ci 85k miles
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11,517 Posts
Discussion Starter #12
balidawg, i haven't seen whole video (just a fraction of the 1st), nor read the thread yet, but i liked your smoke machine, so simple, and looks so easy to use.
Thanks, but I cannot take credit for the simple smoke machine. I think it was jfoj’s post where I first saw it. Pretty much all the information here was taken from a bunch of threads I found when searching this forum for “smoke test”, so really a team effort.
 

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Maybe. It's just more convenient to take the MAF sensor than to remove the intake boot. I guess I could just measure the darn thing. :idea:
I found that a 3" diameter piece of PVC pipe fits nicely into the intake boot with the MAF sensor removed. I then used the nitrile glove connection version over the other end of the piece of pipe sticking out of the intake boot where the MAF was to hook up to the Harbor Freight transfer pump version of a smoke machine.

I suppose that a 3" cap could be bought and glued onto the short piece of 3" diameter pipe and then drilled and tapped/threaded to install the appropriate barbed fitting for a hose to connect to a smoke machine. Just a thought.
 

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'02 330i 5-Speed
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Way too expensive. Just get the Stinger unit for less than half the price.

I suppose that a 3" cap could be bought and glued onto the short piece of 3" diameter pipe and then drilled and tapped/threaded to install the appropriate barbed fitting for a hose to connect to a smoke machine. Just a thought.
Yeah that was the idea. Thanks for the input; 3" is a good place to start.
 

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Wouldn't it be better to take the intake boot with you to Home Depot, so to speak? Since that is what the pvc adapter will plug into to run the smoke test.

Edit: Maybe it doesn't really matter. I've thought about this as well. If a pvc pipe itself happens to fit in the intake boot, then that could also work if cut very short (like 2 inches) and then the corresponding end cap fitted over the end.
I found that 3" diameter PVC pipe worked just fine for me.
 

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Here to serve y’all
2004 330Ci 85k miles
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Discussion Starter #18

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'02 330i 5-Speed
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I'm all for cheap-and-dirty DIYs (the cigar method, etc), but E46s being what they are, there's practically NO chance you'll only have to do just one smoke test. Might as well pay a little more for a robust, reusable tool.
 
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