Vacuum Leak Detector

[force_feed]

This writeup will show you how to use a fog machine to detect vacuum leaks

Everybody here knows its a pain to look for vacuum leaks, and have their own way of finding them. I use to work at this one shop that had a leak detector esp. designed for vacuum leaks

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The down side to these machine is they cost about $1300 dollars.

I was in the process of trying to track down a vacuum leak for a customers car, and decided to make my own smoke machine using a fog machine. And it worked like a charm.

There are different types and size fog machines out there. I bought a 400w fog machine for $29.99 at Party Time. And 1 gallon of Fog Juice $14.00 (check local party store)

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On the front of the fog machine where you see all the holes, that part comes off and will reveal a small copper tube. Follow the copper tube back and you will see a plastic lip that is about 1/16". A vacuum line will fit on that lip perfectly!

Buy a 4 foot 1/16" vacuum line and fit over that lip, that whay you have plenty of hose.

Sit the Fog Machine on a semi flat surface somwhere under the hood. If you sat it on the ground it will not work very well, due to liquid gathering in the vacuum line.

Hook up your vacuum hose from your Fog Machine to any port on your intake, turn the Fog Machine on and look for leaks.
CAUTION the copper tube does get extremely HOT, so don't rune the fog machine for a long period of time. 30 Second burst should be sufficient enough to see a leak.

 

[MLutin]

Simply amazing. I work at Spencers and should be able to pick one up fairly cheap. Will the fog juice residue ruin engine internals? Or coat the intake/lines with anything? Also is there any way to pressurize the system at the same time? Or do you not need to?

 

[AWD_FIEND]

Cool idea, I'm sure it would be very effective. But i'm with MLutin on questioning what the Fog juice consists of for the sake of side effects (pun intended).

 

[chico904]

Cool idea, I'm sure it would be very effective. But i'm with MLutin on questioning what the Fog juice consists of for the sake of side effects (pun intended).

Agreed. What's on the label?

 

[MLutin]

I found this:

Rosco Fog Fluid is composed of a series of glycols of low molecular weight mixed with de-ionized water. The components are all listed on the USFDA Generally Regarded As Safe (GRAS) list and are used extensively in food, food packaging products and cosmetics among many other products.

Don't know what it means for combustible engines, but maybe someone else can help us out with that.

 

[AWD_FIEND]

Well the water is pretty much not an issue as long as the engine doesnt injest to much as one time. Glycol is the main ingredient in Antifreeze, I'll have to do some research regarding its properties. One favorable aspect of glycol is it's slippery...Thanks for the input MLutin.

Glycol is a sur-name for many organic compounds in the alcohol family, so without more info regarding which specific compound the fog contains I can only assume its one of the two following derivitaves.

The first is its most common form Ethylene Glycol which is a colorless oily liquid possessing a sweet taste and mild odor. Its produced from ethylene oxide which is mildly toxic, and is used predominantly in Antifreeze, low-freezing explosives, and brake fluid. It seems to offers molecular stability when subjected to low temperatures for example, stabalizing water when it's rapidly condensed.

Or it could be Propylene Glycol which resembles Ethylene Glycol in its physical properties, but is approved by the FDA for use in products for human consumption. Its found in food (preservative) cosmetics, and oral hygene products. So it's obviously not toxic which coincides with the fact that the Fog Oil is considered safe for human consumpiton. I believe its probably Propylene Glycol. If you consider the fact its an organic compound related to alcohol its probably fine to pass through an engine at idle, while not under load. If an engine was under load while passing the fog through the motor I would expect it might affect the A/F ratios and probably isnt safe. One concern I would have would be the fact that it is slippery in nature which might leave a residue on sensors, but I dont know for sure. Use at your own risk.

 

[force_feed]

Sorry I havent put any imput on this in a while.

I havent had any side effects from using this as a vaccume tester.

Water/Glycol based fog machine fluids are usually a mixture of 99.9% pure, pharmaceutical grade propylene glycol, triethylene glycol, and distilled water

Also, oily residue passes through your intake tract from the pcv valve.

 

[AWD_FIEND]

Yeah, and it causes all sorts of issues internally which is why people vent them or install an inline filter/catchcan. The glycol isnt as thick as oil though so at least it has that going for it. How long have you been using it, honestly?

 

[force_feed]

I've used this method on different cars for about a year now.

 

[MLutin]

sold, thanks man.

 

[Defiant]

A propane torch works wonders, too. Don't light it, just run the nozzle around the vacuum lines. The idle will speed up if it gets sucked in. $6.

 

[AWD_FIEND]

A propane torch works wonders, too. Don't light it, just run the nozzle around the vacuum lines. The idle will speed up if it gets sucked in. $6.

Thats the method I learned to use in school, but the problem is you'll have to apply the torch/gas to every suspected joint one by one until you find the leak. With the Fog method, if it indeed isnt harmful, it will find the leak quickly and automatically without any guess work. Hmmm, a lot to ponder.

 

[Defiant]

A 3' piece of vacuum hose with one end up to your ear works just fine, too.

 

[chico904]

My sisters friend has some sort of fog machine in her attic. I will check it out and if it still works, I will give this a shot.