Intake leak troubleshooting
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Junior User
Joined: Feb 2005
Posts: 66
Likes: 2
From: Surrey, BC
Intake leak troubleshooting
I have a loud whistling sound coming from the intake area on my 300 I-6 engine in my 1965 F100. I've installed an Offy intake and Holley 390 4bbl carb. The engine doesn't idle well and hesistates on acceleration which support that I have an intake leak. I'm not positive where the leak is, although it sounds like it's between the intake and cylinder head around #5 or #6 cylinder.
Before I remove the intake, I would like to identifiy the location and understand why it's leaking so I have a better chance of fixing it. What methods have people used to locate intake leaks. I was thinking of using a propane torch (unlit) to deliver some gas around the intake and hopefully get sucked in by the leak and cause the enigne rpm to increase. Anyone done this before? Is there a better "fluid" or "spray" to use?
Before I remove the intake, I would like to identifiy the location and understand why it's leaking so I have a better chance of fixing it. What methods have people used to locate intake leaks. I was thinking of using a propane torch (unlit) to deliver some gas around the intake and hopefully get sucked in by the leak and cause the enigne rpm to increase. Anyone done this before? Is there a better "fluid" or "spray" to use?
New User
Joined: Mar 2005
Posts: 10
Likes: 0
From: LA
thank for the tips. This helps out on another thread "slight bucking".
BTW, how do you guys avoid a fire?
Any idea where I can get a NON-flammable brake cleaner these days? supposedly that will slow the engine down if it gets sucked in at a leak.
BTW, how do you guys avoid a fire?
Any idea where I can get a NON-flammable brake cleaner these days? supposedly that will slow the engine down if it gets sucked in at a leak.
Elder User
Joined: Feb 2002
Posts: 504
Likes: 2
From: Saddle Brook United State
You can use motor oil, the heavier the better, and an oil can , dribble oil around the suspected leak, the oil will disappear and the idle should change and there may be smoke in the exhaust when you find the leak. Don't use anything flammable, like carb cleaner, or with a low flash point like WD40. Don't use propane whatever you do. You might try soapy water and see what happens. The oil trick works as I used it to find an intake leak in a Pontiac powered 48 Ford I used to have.
stractor
stractor
Cargo Master
Joined: May 2001
Posts: 3,208
Likes: 13
The oil will change the idle when you find the leak. I also use a stethoscope the one I made from one of the auto sethoscopes by changing out the rod for a piece of 3/16 copper tubing run this along the junctions and when you find the leak you will really hear it.
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Junior User
Joined: Feb 2005
Posts: 66
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From: Surrey, BC
To play it safe I ended up using a spray bottle with just water. When I sprayed on the leaks the "whistling" sound changed enough that I located the leak, although it didn't change the idle. Fixed the two leaks and it's running better.
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New User
Joined: Mar 2005
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From: LA
Originally Posted by wtroger
The oil will change the idle when you find the leak. I also use a stethoscope the one I made from one of the auto sethoscopes by changing out the rod for a piece of 3/16 copper tubing run this along the junctions and when you find the leak you will really hear it.
Tried this in the kitchen when I heard a crackling sound behind the sink and found termites, too.
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New User
Joined: Mar 2005
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From: LA
Originally Posted by toque
To play it safe I ended up using a spray bottle with just water. When I sprayed on the leaks the "whistling" sound changed enough that I located the leak, although it didn't change the idle. Fixed the two leaks and it's running better.