Best way to pin point a Vac Leak?

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truckin151

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Alright guys, school me in the best way to pin point/detect a vaccuume leak. I have a feeling since my surging issue and some kr issues have still not gone away that it is now more than likely a vac leak somewhere. I have a strong feeling its coming from my CAI that I made up but need to check everything out.

On another note, since I got a couple weeks off, I will be starting my tear down on the stock HEMI hat, going to open it up, seal off all the chambers to make it a through and through design, smooth out the inside, seal it up and repaint it and see how it does. If it works I got another idea I want to try out but thats a bit more complicated and I need to do some design work for it.
 
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truckin151

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Yeah I got a smoke machine, but I also know how much air is moving undr the hood while its running. I would think that the smoke would just be blown away.
 

AWE Daniel

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You should be able to smoke around where you think it might be leaking and see it pretty easily.
 

Redtruck-VA

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Ryan, it is only a vacum leak if it is behind the TB blade and is a un-metered source of air.
 

Boo Radley

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carb cleaner is what they had us use in mechanic school. any place you hit with the carb cleaner that makes the idle change is a leak. but if its the CAI it wont cause any real harm and not change idle. at worse it will just be unfiltered.
 
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truckin151

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What are the main areas where a vac leak can occure? I know of the TB gasket (where it meats the intake manifold) the brake booster, and I believe there is another line behind the TB on the intake manifold. Any other areas that would be a good place to check?
 

Redtruck-VA

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carb cleaner is what they had us use in mechanic school. any place you hit with the carb cleaner that makes the idle change is a leak. but if its the CAI it wont cause any real harm and not change idle. at worse it will just be unfiltered.

Carb cleaner is not recommended for use on our TB's and apparently will damage the engine electrics. I use a unlit propane torch, but can't recommend it to others for obvious reasons. lol
 

Boo Radley

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Carb cleaner is not recommended for use on our TB's and apparently will damage the engine electrics. I use a unlit propane torch, but can't recommend it to others for obvious reasons. lol

Carb cleaner is fine as long as you don't spray it directly down into the throttle body. You are looking for a leak at a hose or gasket, not inside the throttle body. I use carb cleaner for this every day and so do the Mopar certified teaching techs I work with.
 
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truckin151

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So carb cleaner is what the dodge techs use and you are just looking for a rais in the idle. Good to know.

What are the main areas where a vac leak can occure? I know of the TB gasket (where it meats the intake manifold) the brake booster, and I believe there is another line behind the TB on the intake manifold. Any other areas that would be a good place to check?
 

Redtruck-VA

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Carb cleaner is fine as long as you don't spray it directly down into the throttle body. You are looking for a leak at a hose or gasket, not inside the throttle body. I use carb cleaner for this every day and so do the Mopar certified teaching techs I work with.

Boo, don't mean to sound critical and don't really care what you use daily on other people's rides. But there must be a reason the manual says don't use carb cleaner and being a certified chrysler mechanic use to mean a little more to me than it does today as my local dealer with it's CM's have failed in performing a simple PCM reflash, plus they were more interested in test driving my truck to see how it ran then in getting anything right. That dealer with it's certified mechanic's was no guarantee to having the job done right.
 
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