Checking for Vacuum Leaks
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Senior User
Joined: May 2004
Posts: 120
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From: Vandenberg Air Force Base
Checking for Vacuum Leaks
Hello all,
With all of the computer controls on engines these days, how do you find vacuum leaks? Basic question, but in the golden days of carbs, I used ether or WD-40 to find the leaks. Today the computer seems to adjust faster than I can pick up on a change. How do you pinpoint a leak? Like an intake manifold leak? Do you disconnect something before spraying around hoses and mating surfaces?
Does the system have to be in open loop for the spray test to work?
Please help out this heavy junk mechanic, thanks in advance.
With all of the computer controls on engines these days, how do you find vacuum leaks? Basic question, but in the golden days of carbs, I used ether or WD-40 to find the leaks. Today the computer seems to adjust faster than I can pick up on a change. How do you pinpoint a leak? Like an intake manifold leak? Do you disconnect something before spraying around hoses and mating surfaces?
Does the system have to be in open loop for the spray test to work?
Please help out this heavy junk mechanic, thanks in advance.
Last edited by SgtJoe; Dec 26, 2004 at 04:50 PM. Reason: Clarify
Laughing Gas
Joined: Jun 2004
Posts: 1,240
Likes: 3
From: Dallas, Texas
You can use propane, Throttle body cleaner. The intake is the tricky part. You have to make sure the thing is sealed good or you get bad readings. If the seal around the body or air cleaner is bad you will know real fast.
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Joe if your scan tool will let you watch fuel trims in real time while the engine is running that helps a lot too. If you watch them while you spray carb cleaner or whatever you're using (I like Carb-Medic) you'll see the short term fuel trims take a big drop if you hit a leak with the spray.
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