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How to find vacuum leaks...

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Old 02-14-2009, 08:29 AM   #1
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How to find vacuum leaks...

My car is low on horsepower nowadays, and I'd like to find the source of the problem. One of my buddies mentioned that I might have a vacuum leak. I don't really see how it would happen, because after I put my intake spacers on, the car was running strong for a good while. But I'd like to eliminate all possibilities, so how do I check the car for vacuum leaks? Thanx
-Chris
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Old 02-14-2009, 09:09 AM   #2
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The way I prefer to do it is using compressed air with a blowgun, tee'd into a pressure gauge and the intake manifold, cap off the throttle-body with a 3" pvc expandable plug available in the plumbing section of home depot, and also cap off the pvc line that comes from the front valve cover. Pump it up with no more than 10psi, use soapy water to find the leaks if you have any. If you hear air bleeding out of the exhaust you might be on an overlap on one cylinder & you'll need to bump the starter. Hope this makes sense.
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Old 02-14-2009, 09:11 AM   #3
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Option #2 (easier & cheaper): Get an automotive stethescope, take off the end so you have just an earpeice & hose (You can also use a stethescope). Use the hose to listen for any vacuum leaks, also works well for exhaust leaks, and the stethescope part works great for diagnosing engine noises, accessories like idler pulley, alternator, powersteering, etc.
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Old 02-14-2009, 09:18 AM   #4
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Or you can turn the car on, and start spraying tb cleaner until you hear the engine start to stumble. This way you will narrow down the location.
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Old 02-14-2009, 11:37 AM   #5
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Originally Posted by KRRZ350 View Post
Option #2 (easier & cheaper): Get an automotive stethescope, take off the end so you have just an earpeice & hose (You can also use a stethescope). Use the hose to listen for any vacuum leaks, also works well for exhaust leaks, and the stethescope part works great for diagnosing engine noises, accessories like idler pulley, alternator, powersteering, etc.
what areas would i listen for these noises? and i would listen for like an air leak, right?
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Old 02-14-2009, 12:40 PM   #6
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Propane or butane applied around hoses while the engine is running. When it stumbles/surges, you've found the leak.
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Old 02-14-2009, 07:11 PM   #7
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You can either spray something flammible like throttlebody/carb cleaner around suspected areas...or heck, even water will do. As soon as the engine changes revs or sound, you've found something.
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Old 02-14-2009, 09:25 PM   #8
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this all sounds like a great way to harm your engine
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Old 02-14-2009, 09:35 PM   #9
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this all sounds like a great way to harm your engine
*Sigh*

Really.
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Old 02-14-2009, 09:43 PM   #10
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use Carb Cleaner. That's what I use. works great. DON'T USE PROPAIN
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Old 02-16-2009, 03:41 PM   #11
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i think i'd feel safer using an automotive stethoscope.. so what areas of the engine would i listen for intake leaks? i'm assuming everything from the air filter back to the throttle body.. around the IM where it bolts down... any other places?
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Old 02-16-2009, 04:30 PM   #12
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Carb cleaner is the way people have been doing it for years.

As everyone says when it stumbles you've found your leak.

A mist if water also works well. The water mist will seal the leak and cause things to smooth out.
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Old 02-16-2009, 05:43 PM   #13
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Have you used a vacuum gauge to what the engine is pulling?
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Old 02-16-2009, 07:00 PM   #14
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Carb cleaner is the way people have been doing it for years.

As everyone says when it stumbles you've found your leak.

A mist if water also works well. The water mist will seal the leak and cause things to smooth out.
alright, well on what components would i spray the carb cleaner/water mist to test it?

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Have you used a vacuum gauge to what the engine is pulling?
i don't really understand your question, but i've never used a vacuum gauge before
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Old 02-17-2009, 04:55 AM   #15
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alright, well on what components would i spray the carb cleaner/water mist to test it?
With the engine running and warm (since leaks are sometimes not there when cold) you want to spray along all of the vacuum lines especially at connection points.

Things could be leaking at a connection or a hose could have rubbed on a hard point and worn through.

Sometimes the plastic hose T's get cracked and leak also.

Good luck
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Old 02-17-2009, 12:59 PM   #16
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Originally Posted by fflint_18 View Post
With the engine running and warm (since leaks are sometimes not there when cold) you want to spray along all of the vacuum lines especially at connection points.

Things could be leaking at a connection or a hose could have rubbed on a hard point and worn through.

Sometimes the plastic hose T's get cracked and leak also.

Good luck
well, i gotta rip off my IM today to change my valve covers and spark plugs today anyway, so i can look out for cracks to the plastic pieces.. and the vacuum lines are all those little hoses that connect to the intake manifold right?
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Old 02-18-2009, 09:10 PM   #17
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carb cleaner, tb cleaner, brake cleaner, they all work
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Old 02-19-2009, 12:24 AM   #18
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All the above: stethoscope (hose only), ultrasonic leak detector, carb cleaner, parts/brake cleaner, etc....listen around all intake manifold mating surfaces and hoses... also another old school way was to parially/sufficate the engine at the carb inlet and it make the leak more pronouced so you could locate it. This would be easy as hell for the WAI boys or short ram boys!
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Old 05-20-2010, 08:04 PM   #19
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bumping a old thread, my car has a vacuum leak and I'm doing 55 in the right lane till it's fixed, I will try these solutions tomorrow.
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