Best techniques for finding vacuum leaks...?

[SuperTramp]

I’ve never checked for vacuum leaks on my ‘98 5.7 k2500. I’ve had some inconsistent engine idle and haven’t been able to find a simple and efficient technique for finding leaks. Thanks in advance for your help. Wes


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[Bear 77]

Wrong place for that question


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[Erik the Awful]

Use your eyeballs and look at any place that seals the airflow after the throttle plates.

You can use a can of WD-40 and spray it around to see if the idle rises, but beware that if your driveability problem is caused by a leaky spark, WD-40 is also flammable.

 

[evilunclegrimace]

Technically there is no such thing as a vacuum leak.

 

[kennythewelder]

There are 2 ways that work best. 1- they make a smoke machine just for this. Simply unhook a vacuum line and plug in the smoke machine. It pumps smoke into the whole system, then you look for smoke leaking.
2- use a propane torch, unlight and run ot over the intake,and vacuum lines slowly with the engine started and at idle. If the engine speeds up there is your leak. Engine will suck in the propane where there is a leak, making the idle speed up.

 

[evilunclegrimace]

There are 2 ways that work best. 1- they make a smoke machine just for this. Simply unhook a vacuum line and plug in the smoke machine. It pumps smoke into the whole system, then you look for smoke leaking.
2- use a propane torch, unlight and run ot over the intake,and vacuum lines slowly with the engine started and at idle. If the engine speeds up there is your leak. Engine will suck in the propane where there is a leak, making the idle speed up.

These are both good ways to find air leaks.

 

[Supercharged111]

I've had good luck with a can of carb cleaner. That'll make the engine idle up too.

 

[Erik the Awful]

2- use a propane torch, unlight and run ot over the intake,and vacuum lines slowly with the engine started and at idle. If the engine speeds up there is your leak. Engine will suck in the propane where there is a leak, making the idle speed up.

Make sure your spark plug wires are good before you try this one. There's a reason I made note that WD-40 is flammable. I saw a guy try to locate a vacuum leak with WD-40, but instead the misfire was caused by spark jump. The WD-40 made a nice little fire. Propane could get a lot more fun.

 

[andy396]

There are 2 ways that work best. 1- they make a smoke machine just for this. Simply unhook a vacuum line and plug in the smoke machine. It pumps smoke into the whole system, then you look for smoke leaking.
2- use a propane torch, unlight and run ot over the intake,and vacuum lines slowly with the engine started and at idle. If the engine speeds up there is your leak. Engine will suck in the propane where there is a leak, making the idle speed up.

When I was trying to figure out my vacuum issues I made one out of a paint can, a tiki torch wick, resistance wire and some hose fittings. I even put some engineering into it by measuring out the length of the resistance wire to be right at the smoke point temperature of if baby oil when hooked to a 12.8V car battery. It works pretty well.

At that time I also learned that the propane trick only works on *external* leaks, which mine was not, hence the motivation to build the smoke machine.

 

[SuperTramp]

Thanks for your responses.


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