Vacuum leak detection

chevyman · 03-08-2009, 09:10 AM

With some encouragement I post this tip for anyone searching for a vacuum leak.
Use an unlit propane torch opened 1/2 way to follow all vacuum lines, carbs, intakes, anywhere there is a chance for vacuum leak. If the propane finds its way into the a/f mix, engine RPM will increase. When that happens go back along the section you just went over to pinpoint the leak.

A small hose attached to the end can allow you to get it in tight places as well. The propane idle tool readily available works great for this as well.

There is no mess to clean up afterward and it wont harm rubber or paint like other methods.

Happy Riding

Barb · 03-08-2009, 09:13 AM

OK , I don't get it, can you explain it for me. a/f ? is that air/fuel? Why does this work?

70super · 03-08-2009, 10:00 AM

Carb cleaner also works well.

chevyman · 03-08-2009, 10:53 AM

Yes, A/f is air fuel mixture. It speeds the engine up by replacing the excess air that would normally enter through the vacuum leak with propane a combustible. More combustible in the mix speeds up the rpm temporarily. Carb cleaner works too but can cause some damage to certain materials.

Barb · 03-08-2009, 10:55 AM

Quote:

Originally Posted by chevyman

Yes, A/f is air fuel mixture. It speeds the engine up by replacing the excess air that would normally enter through the vacuum leak with propane a combustible. More combustible in the mix speeds up the rpm temporarily. Carb cleaner works too but can cause some damage to certain materials.

Wow, very impressive and cool! Is this your invention?

static · 03-08-2009, 11:16 AM

Its an old school tip that works really well. I havent had to locate a vacuum leak in so long i had forgotten about it. Thanks for reminding me.

arkie6 · 03-08-2009, 11:17 AM

You can also use the unlit propane torch into the airbox inlet to determine if your idle mixture is too rich or too lean - if too lean then the idle speed will increase, if idle mixture is just right then idle speed may show slight decrease, if mixture is already too rich then idle speed will show a decrease.

chevyman · 03-08-2009, 11:47 AM

That is also a good tip. They make a "special" tool for that.

This is not my idea at all. Learned it about 10 years ago from my autoshop teacher. Came up in another post.

03-08-2009, 09:10 AM	#1
chevyman Registered User Join Date: Jul 2008 Location: WI Posts: 216	Vacuum leak detection With some encouragement I post this tip for anyone searching for a vacuum leak. Use an unlit propane torch opened 1/2 way to follow all vacuum lines, carbs, intakes, anywhere there is a chance for vacuum leak. If the propane finds its way into the a/f mix, engine RPM will increase. When that happens go back along the section you just went over to pinpoint the leak. A small hose attached to the end can allow you to get it in tight places as well. The propane idle tool readily available works great for this as well. There is no mess to clean up afterward and it wont harm rubber or paint like other methods. Happy Riding __________________ "The true hotrodder is only satisfied by a machine so powerful that full throttle results in death by acceleration!" "If loud pipes save lives, why do some many of those who own them crash?"

03-08-2009, 10:00 AM	#3
70super Looking for Tardfest Join Date: Apr 2003 Location: Greensburg (near Pittsburgh), PA Posts: 17,904	Carb cleaner also works well. __________________ He who is not aware of his ignorance will be only misled by his knowledge. - Richard Whatley

03-08-2009, 10:53 AM	#4
chevyman Registered User Join Date: Jul 2008 Location: WI Posts: 216	Yes, A/f is air fuel mixture. It speeds the engine up by replacing the excess air that would normally enter through the vacuum leak with propane a combustible. More combustible in the mix speeds up the rpm temporarily. Carb cleaner works too but can cause some damage to certain materials. __________________ "The true hotrodder is only satisfied by a machine so powerful that full throttle results in death by acceleration!" "If loud pipes save lives, why do some many of those who own them crash?"

03-08-2009, 11:16 AM	#6
static Its Gonna be fun Join Date: Sep 2006 Location: Seattle/Tacoma Posts: 3,001	Its an old school tip that works really well. I havent had to locate a vacuum leak in so long i had forgotten about it. Thanks for reminding me. __________________ Last edited by Static: 2009/09/02 11:29:32 Government: If you think the problems they create are bad, wait till you see their solutions. Gravity can be a cruel mistress, mock her and she will bitch slap you to the ground.

03-08-2009, 11:47 AM	#8
chevyman Registered User Join Date: Jul 2008 Location: WI Posts: 216	That is also a good tip. They make a "special" tool for that. This is not my idea at all. Learned it about 10 years ago from my autoshop teacher. Came up in another post. __________________ "The true hotrodder is only satisfied by a machine so powerful that full throttle results in death by acceleration!" "If loud pipes save lives, why do some many of those who own them crash?"

03-08-2009, 09:13 AM	#2
Barb Registered User Join Date: May 2004 Location: Florida Posts: 24,544	OK , I don't get it, can you explain it for me. a/f ? is that air/fuel? Why does this work?

03-08-2009, 11:17 AM	#7
arkie6 Registered User Join Date: Oct 2003 Location: Russellville, AR Posts: 4,321	You can also use the unlit propane torch into the airbox inlet to determine if your idle mixture is too rich or too lean - if too lean then the idle speed will increase, if idle mixture is just right then idle speed may show slight decrease, if mixture is already too rich then idle speed will show a decrease.

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