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sixer
Samba Member
Joined: March 23, 2014
Posts: 88
Location: Charleston, SC
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 Posted: Mon Feb 23, 2015 7:28 pm Post subject: Finding vacuum leaks with smoke (smoke test, tester) |
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| [url=http://www.thesamba.com/vw/forum/viewtopic.php?p=7568752#7568752]Finding vacuum leaks with smoke (smoke test, tester)[/url] |
Hi all,
A quick write up for this forum, since I couldn't find it when I was searching earlier. I recently had some vacuum leak woes. I built a smoker to make it easier to find them. Based on this design over in the Vanagon forum: http://www.thesamba.com/vw/forum/viewtopic.php?p=5282178
Parts required:
- Quart paint can
- 1/8" barbed to NPT fitting
- Valve stem
- JB weld, epoxy, something gluey.
Instructions:
1) Drill two holes in the lid, one for the barbed fitting, one for the valve stem.
2) Insert barbed fitting, pot with epoxy or JB weld.
3) Install Valve stem
To use:
1) Hook up a pump to the valve stem (I used a manual bike pump).
2) Hook up a vacuum line from the barbed fitting to a place in the vacuum system.
3) Block S-boot with a beer bottle.
4) Light something on fire in the can. I used a scrap of t-shirt soaked in gas and oil, along with some cardboard.
5) Put the fire out, pop the lid on, start pumping the air pump and look for smoke.
Relevant pictures below:
| GoBigEmma wrote: |
That's a cool setup! We copied it to check for vacuum leaks, but we used smoke bombs that I used to make as a kid instead of cigarettes: Wrap a ping pong ball in aluminum foil (make sure to wrap it tight or it will burn, but not smoke) and hold a flame under one spot of it until it starts smoking. Produces a whole lot of smoke (like, A LOT), but breathing that stuff in definitely shortens your life by the smell of it, so be careful.  |
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http://instagram.com/sixer.bus/ |
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PITApan
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Joined: November 09, 2014
Posts: 1058
Location: Northern Colorado
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| Posted: Mon Feb 23, 2015 7:46 pm Post subject: |
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I've always found starter fluid to be very sensitive but I hear unlit propane from your torch works well too. In a few situations I've found leaks with vaseline.
What's the advantage of building a smoker? |
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sixer
Samba Member
Joined: March 23, 2014
Posts: 88
Location: Charleston, SC
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| Posted: Mon Feb 23, 2015 7:58 pm Post subject: |
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I tried the propane torch trick, it didn't work very well for me. I wasn't a fan of spraying starter fluid on my freshly cleaned and painted engine, so I built the smoker. Worked really well so far for me, and for ~$10 I have a new tool for diagnosing. I'll probably add smoking the vacuum lines to my tune up list just because it's easy to do and keep the FI system happy.
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1976 Transporter, Stock 2.0L
http://instagram.com/sixer.bus/ |
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PITApan
Samba Member
Joined: November 09, 2014
Posts: 1058
Location: Northern Colorado
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| Posted: Mon Feb 23, 2015 8:08 pm Post subject: |
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| sixer wrote: |
| I tried the propane torch trick, it didn't work very well for me. I wasn't a fan of spraying starter fluid on my freshly cleaned and painted engine, so I built the smoker. Worked really well so far for me, and for ~$10 I have a new tool for diagnosing. I'll probably add smoking the vacuum lines to my tune up list just because it's easy to do and keep the FI system happy. |
Gotcha.
For $4.00 I got a pack of camels and a rubber hose.  |
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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Mal evolent
Samba Member
Joined: March 31, 2009
Posts: 2912
Location: San Antonio, Nuevo Mexico
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| Posted: Tue Feb 24, 2015 6:52 am Post subject: |
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I do the opposite. soap everything, pressurize the air intake to 2 PSI, watch the bubbles.
can't bring myself to fill the engine compartment with propane and generate sparks. downright Darwinian.
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raygreenwood
Samba Member
Joined: November 24, 2008
Posts: 21513
Location: Oklahoma City
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| Posted: Tue Feb 24, 2015 10:04 am Post subject: |
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Smoke and propane are not capable of finding really small/fine vacuum leaks....especially the type that, open up larger with heat expansion and vibration.
Typically these are very thin leaks less than .001" in space ...on items like runner boots and flat intake runner seals etc.
These types of leaks are rarely large by themselves. Its usually several of them creating a cumulative leakage......which fuel injected systems are very sensitive too. Usually finding these types of leaks is the final stage in really fine tuning.
There is usually either not enough airflow through these leaks or not at the time and rpm you are testing.....which is why smoke and propane do not work In these cases.
However smoke and propane work well on cracked hoses, fittings etc.
Solvents like carb cleaner work well on the types of leaks that smoke does not work on because.....its thin enough to get into crevices and highly flammable. However its also hard on paint and coating.
If you have time a very thin machine oil in a dripped bottle for checking seals you suspect can work well. In some cases.....just soap water works well as others have noted.
You need to use soap to break the surface tension or the water so it gets into very narrow leaks. You can also use Jet-Dry for dishwashers. Mixed with water it makes a good leak checking liquid. Ray |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Wed Sep 16, 2015 7:51 am Post subject: |
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windex often will turn up a leak without stripping paint off.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
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| Posted: Wed Sep 16, 2015 9:34 am Post subject: |
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| Mal evolent wrote: |
| I do the opposite. soap everything, pressurize the air intake to 2 PSI, watch the bubbles. |
This is a great way to do it. Because you are under positive pressure. Leaks that may close up under negative vacuum open up.
For when soap and water won't cut it.
Tire Leak Detectors SPC 35805
Good day
Tcash |
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meester_jamie
Samba Member
Joined: June 14, 2005
Posts: 24
Location: Southern Ontario Canada
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| Posted: Tue Dec 08, 2015 8:48 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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situation,, engine won't start,, looked like crazy for a vac leak.. can't find it.. blow smoke thru into the intake... and see it coming out under the front wheel !! holy crow.. the vac hose is bust at the brake booster.
 I am thinking out loud.. but a bicycle tube , cut to appear to be a hose.. one end stretched over the S boot... and the other end on the smoke source.. lol.. I don't know if you can take a big TOKE on see gar,, and Huff it enough to make it fill the intake system enough to appear thru a leak... but I guess if the leak is right there,, and big enough.. it might just work.. otherwise a vacuum cleaner might add enough blow to make the smoke rise
you tube has plenty of cheap home made cigar smoke machines to let you adapt .. |
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kkjellquist
Samba Member
Joined: June 04, 2013
Posts: 752
Location: Asheville, NC
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| Posted: Mon Mar 14, 2016 5:15 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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Just a bump for this helpful thread and a big thanks to OP. Built one of these and found 2 small leaks. Tool cost me about $10 to build and I fixed the leaks with $3 in hose clamps! My bus idles better now.
One tip for others, a 12V air mattress pump works perfectly and you can run it right off the battery of course. A completely portable vacuum leak tester 
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(1978 2L FI, Pertronix, Hydraulic Lifters)
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busmania
Samba Member
Joined: October 13, 2006
Posts: 1934
Location: Here
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| Posted: Tue Jun 28, 2016 7:19 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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I am about to build this handy contraption but had a few questions.
I assume you look for leaks with the engine OFF? Plug S boot and then introduce the smoke to ANY of the vacuum lines? The smoke will then leak out of wherever the leak is, correct?
Sometimes I have a hard time visualizing things. So thank you! |
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SGKent
Samba Member
Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Tue Jun 28, 2016 7:24 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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engine off. You are looking where smoke escapes.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin |
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Tcash
Samba Member
Joined: July 20, 2011
Posts: 12844
Location: San Jose, California, USA
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| Posted: Tue Jun 28, 2016 8:51 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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| busmania wrote: |
I am about to build this handy contraption but had a few questions.
I assume you look for leaks with the engine OFF? Plug S boot and then introduce the smoke to ANY of the vacuum lines? The smoke will then leak out of wherever the leak is, correct?
Sometimes I have a hard time visualizing things. So thank you! |
https://www.youtube.com/results?search_query=smoke+test+vacuum+leak |
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busmania
Samba Member
Joined: October 13, 2006
Posts: 1934
Location: Here
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| Posted: Tue Jun 28, 2016 11:58 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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| Tcash wrote: |
| busmania wrote: |
I am about to build this handy contraption but had a few questions.
I assume you look for leaks with the engine OFF? Plug S boot and then introduce the smoke to ANY of the vacuum lines? The smoke will then leak out of wherever the leak is, correct?
Sometimes I have a hard time visualizing things. So thank you! |
https://www.youtube.com/results?search_query=smoke+test+vacuum+leak |
As a visual learner, this helps a ton. thank you.
Now when my wife is mad because I'm in the garage "smoking" cigarettes (I quit years ago), i'll point her to the home made red neck smoke machine video.
https://www.youtube.com/watch?v=rumgJ5UBpCw
Thanks again. |
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GoBigEmma
Samba Member
Joined: January 25, 2016
Posts: 209
Location: Currently scattered between Mexico and Illinois
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| Posted: Wed Jun 29, 2016 7:09 pm Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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| sixer wrote: |
| I recently had some vacuum leak woes. I built a smoker to make it easier to find them. |
That's a cool setup! We copied it to check for vacuum leaks, but we used smoke bombs that I used to make as a kid instead of cigarettes: Wrap a ping pong ball in aluminum foil (make sure to wrap it tight or it will burn, but not smoke) and hold a flame under one spot of it until it starts smoking. Produces a whole lot of smoke (like, A LOT), but breathing that stuff in definitely shortens your life by the smell of it, so be careful.
_________________
1975 Bus "Big Emma", 1.8 FI, Hydraulic lifters
Interrupting our Pan-American Roadtrip for post-flood repairs: http://www.thesamba.com/vw/forum/viewtopic.php?t=657738
Follow the trip on our blog: http://www.gobigemma.com |
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ac78
Samba Member
Joined: March 18, 2008
Posts: 330
Location: Nashville
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| Posted: Mon Aug 29, 2016 6:02 pm Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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| GoBigEmma wrote: |
| sixer wrote: |
| I recently had some vacuum leak woes. I built a smoker to make it easier to find them. |
That's a cool setup! We copied it to check for vacuum leaks, but we used smoke bombs that I used to make as a kid instead of cigarettes: Wrap a ping pong ball in aluminum foil (make sure to wrap it tight or it will burn, but not smoke) and hold a flame under one spot of it until it starts smoking. Produces a whole lot of smoke (like, A LOT), but breathing that stuff in definitely shortens your life by the smell of it, so be careful. |
I don't even remember why I'm looking at this thread, but Eureka! Smoke Bombs, Brilliant! I can get those year round in TN. You may not even need to add air pressure with those.Thank you GoBigEmma! I'll have to try it just because...
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78 Westy 2.0l hydr. FI
VW Campmobile
For people who believe a family's
car should be it's castle ! |
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Terminatez
Samba Member
Joined: June 07, 2015
Posts: 340
Location: Sun Valley, CA
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| Posted: Tue Dec 12, 2017 9:03 pm Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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So, how would I do a vacuum test using a smoker when I have carbs?
I'm guessing I can blow the smoke through the hose used for vac to the booster?
What do I need to cap off, and how?
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1972 Westfalia P30 hardtop Campmobile [On-going Restoration]
| aeromech wrote: |
| I don't think I've ever seen an engine in worse shape. |
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timvw7476
Samba Member
Joined: June 03, 2013
Posts: 2200
Location: seattle
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| Posted: Wed Dec 13, 2017 12:48 am Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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| Terminatez wrote: |
So, how would I do a vacuum test using a smoker when I have carbs?
I'm guessing I can blow the smoke through the hose used for vac to the booster?
What do I need to cap off, and how? |
Nitrile or latex work gloves work well as blockers on carb intakes,
they tend to snap right over modern throttle bodies but you can tear a palm
shaped piece out of one & use a rubber band or air filter clamp/zip tie
to seal carb throat. If you are running an open breather set up, plug that as well. Booster line is where I usually stuff the smoke. |
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aeromech
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Joined: January 24, 2006
Posts: 16961
Location: San Diego, California
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| Posted: Wed Dec 13, 2017 12:48 pm Post subject: Re: Finding vacuum leaks with smoke (smoke test, tester) |
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Cap the exhaust pipe too. Remember, when you find the first leak plug it anyway you can and keep going, finding and plugging, until you find ALL the leaks. Don't forget to check around your exhaust system too
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