Smoke test/air leak for dummies
 

Okay,

I'm about to purchase a smoke detector/machine for vacuum leak investigation on my 911. I see the really nice one is close to 900-1000 dollars (at least I quit smoking 25+ years ago so I've saved enough to pay for it :)).

Seriously One which provides 1 psi good enough?
Stinger brand at amazon 150$
I plan on getting a cone to insert in the throttle body too.
Not sure this link works for everyone, Amazon is taking over the world.

https://www.amazon.com/STINGER-Smoke-Machine-Adapter-Manifolds/dp/B0758ZRBT7

I bought an ebay cheapo one that's made out of a paint tin - worked ok the first time I used it. Not sure it's actually safe ... I think it was maybe $30. That looks to be a nice piece of kit for $150 but that's a little bit of dough. I thought about maybe a party smoke machine. I think those are relatively cheap. There is also the cigar method but I've never smoked in my life so that didn't appeal to me at all.

There is also the "tony" test named after boyt991sc - using the reverse vac cleaner technique, spray soapy water everywhere and see what bubbles. You have to remove the CIS "hat", plug the throttle body and tail pipe. That's really cheap. Smoke will find even the smallest leaks though.

Smoke tester........
 

Gary,

I never used the vacuum cleaner for the test. It was Thomas Tree from UK who did it. The air pressure created by the vacuum cleaner is too much and excessive. All you need is a continuous air supply at 1~2 psi. This is more than sufficient to locate the sources of vacuum leak in the system.

A smoke tester is much better and convenient. I made one for less than $30 and been using it for a couple of years now with remarkable success. A few months ago, a local guy asked me to take a look at his ‘83 SC that was recently had work done at a shop.

To make the story short, I suspected there was significant vacuum leak and the shop set the mixture too RICH to compensate for the problem. To confirm my suspicion, I hooked up my smoke tester and within seconds the engine was showing air leaks in several spots. Case closed.

http://forums.pelicanparts.com/uploa...1552530964.jpg
http://forums.pelicanparts.com/uploa...1552530964.jpg

You could make a similar smoke tester using a 20 gauge Nichrome wire and some wick.
And baby oil from the Dollar store and a gallon paint can. Plus some hardwares and plastic tubing. Total budget: $30~$40.

Tony

Thanks guys,

I was hoping Tony would provide his knowledge to this, I got my wish.

So, Tony is 1 psi enough, or might I need 2 psi for finding elusive air leaks?
I like the DIY smoke machines, if I’d have been a better planner I might have made one by now :). Sadly, time is getting squished :D

I made one but used a soldering iron..put just the tip in the baby oil and it will smoke away. There are videos on YouTube about it...good luck

Where on a 3.2 do you attach the Stinger or any smoke machine to check for vacuum leaks?

Not sure on a 3.2, on 3.0 a popular place is in the throttle body. Amazon has a cone which appears to fit in the throttle body. Some claim the exhaust but this seams opposite to the vacuum flow.

Throttle body for 3.0 I say! I’m a risk taker though. And I’m talking 3.0 SC, not 2018 911 turbo 3.0 :p

I read somewhere someone (I won't name names) used a cigar.

Smoke generator.........
 

Mike,

1 or 2 psi. or even less will more than sufficient to locate these hard to find air leak sources. What you need is a decent smoke generator and low air pressure. Your air compressor or electric tire inflator could deliver the needed air pressure for the test. Four (4) psi. or more will lift up the POV. You need a low amount of positive pressure to test the POV for leak too. If you don’t have a POV, then you could use more air pressure.

Tony

Hey Tony, good to know on the vacuum cleaner. That's the same kind of smoke tester I have too. It works great.

Thank you Tony

So can I take the vacuum hose off say the CPR (Control Pressure Reg) and plug the output of my smoke machine in same hose to check for air leaks? Or is the throttle body (Plug in a thight fitting cone say) a better way to test for air leaks?

Let’s make it simple........
 

Mike,

The objective is to create a positive air pressure in a system and locate the escaping air. Either do it with smoke or spray with soapy water for visual inspection. There are several points or locations in a CIS engine where you could inject the pressurized air (with or without) namely:
a). Fuel injector port/s.
b). POV
c). Brake boosted vacuum port by the side of the air box.
d). Throttle body.
e). Any existing vacuum lines.
f). And many more.

For simple show and tell, I used toy balloon to demonstrate when you have a positive air pressure and then spray soapy water everywhere you want to inspect. But smoke generator does a better way than soapy water.

For example, you want to test the air box for air leak. First thing you need is to isolate the air box and plug all the orifices around it. While under pressure, you could submerge the CIS airbox in a tub of water. Any air leak would be visible. But this method is too cumbersome. A smoke generator with 1 or 2 psi. air does the same thing. Faster and effective.

Tony

Well a learning curve for me for sure. I got my machine hooked up and smoke generated nicely! Plugged the output into a couple of different places and both yielded a unexpected result: Smoke pouring out from under the airflow sensor with the boot on. Plugged the smoke output into the CPR vaccum line, and tried the dizzy line with same results.

I'll try smoke down the throttle body soon with the boot off next. And report.
Hope the smoke from the sensor plate was expected, it was so much smoke I could not see any other leaks.

So is smoke pouring out from under the air flow sensor plate the expected result? I expect it was.

Video can be made available :)

Smoke test......
 

Mike,

The air flow sensor should not be included in the smoke test. The sensor plate is under atmospheric condition. You need to block the throttle body and the two (2) vacuum hoses that were connected to the “Pope” rubber boot.

Tony

Here is a few photos during my smoke testing for my engine.http://forums.pelicanparts.com/uploa...1553191803.jpg
http://forums.pelicanparts.com/uploa...1553191816.jpg
http://forums.pelicanparts.com/uploa...1553191833.jpg

Tony,

What is the “Pope” rubber boot?
Block the throttle body to keep it from leaking into the air flow sensor, correct?
I know closing the throttle all the way does not do it!

Throttle body intake boot......
 

Someone referred to the CIS throttle body rubber boot as the “Pope hat”. So for convenience, I began to use it too. Borrowed pic from a sale ad in the classified section.

http://forums.pelicanparts.com/uploa...1553254728.jpg

Tony

Thanks, makes sense. Will try again.

For a sec I thought you meant I need prayer from the papacy to find my air leaks ;)
But it might not hurt!