Home remedy for smoke/vacuum testing

hans747

Well-Known Member
Joined
Feb 20, 2007
Location
Asheville, NC
Hey guys,

I've been hunting down a vacuum leak in my friend's car, but having no luck (you wouldn't believe the number of hoses under that hood). I've heard that shops will pump smoke into the vacuum lines to spot where the leak is. I thought about buying a cheap cigar at the convenience store, but I don't think I could produce enough volume to fill the system adequately.

Any suggestions on how I can produce the same results?
 
best way is to spray wd-40 on the vacuum lines one at a time. a rise in engine rpm indicates where the leak is.
 
rustyolred said:
best way is to spray wd-40 on the vacuum lines one at a time. a rise in engine rpm indicates where the leak is.
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Brake or carb cleaner would be preferable as it wouldn't leave an oily messy residue to contend with during the search.

I've also used a propane torch (unlit) lightly flowing gas to narrow down the area of the leak.

Also, knowing what vehicle in question could help, many vehicles have common fail characteristics that from the begining could seem isolated.
 
I'm not sure if this would work or not, but I heard it on Click 'N Clack one day. A guy was hunting a vacuum leak so he started swapping plug wires, got the engine to backfire through the intake, and smoke came out where the vacuum leak was. I'm not sure if the story was true, or if I even told it correctly, but it's something someone else might know more about.
 
JoshRountree said:
I'm not sure if this would work or not, but I heard it on Click 'N Clack one day. A guy was hunting a vacuum leak so he started swapping plug wires, got the engine to backfire through the intake, and smoke came out where the vacuum leak was. I'm not sure if the story was true, or if I even told it correctly, but it's something someone else might know more about.
Click to expand...

Doing that could cause problems from blowing out the power valve on a Holley to cracking a plastic intake on a newer car..
 
Rich said:
Doing that could cause problems from blowing out the power valve on a Holley to cracking a plastic intake on a newer car..
Click to expand...

but if he found the vacuum leak.....:flipoff2:
 
there's a better way than intentionally causing a misfire. put a small amount of tranny fluid in a container and with the engine running remove a known good vacuum line and place in the fluid. the vacuum will suck it up and should smoke out of any leaks. hope it helps.
 
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