Vacuum leak detection

[robfg67]

I suspect a vacuum leak on my 4.0 engine. I've seen posts on using an unlit propane tank or a can of starter fluid and then listen for the engine to race.

 

Would compressed air work as well?

[jtdesigns]

no... compressed air has nothing thats flammable. Its the flammable properties of lp and starter fluid that raises the idle.

[Randy in Maine]

Actually compressed air can work pretty well.

 

I have a little gizmo that I made from cheap stuff and some fittings in the shop (garden sprayer + cone incense burner + vacuum fittings and hose) that plugs into the vacuum sysem with the car off and some "cling wrap" over the air inlets and it does OK for what it cost ~ $15 to build. I only pressurize it to about 4-5 pounds though. I was looking for smoke coming out of any vacuum leaks.

 

SnapOn has a really nice one that does a better job but it costs about $3K.

[carnuck]

I've fixed minor vacuum leaks with silver spray paint. Get the motor to operating temp, spray the affected area, shut it off and spray again then let it sit and dry (old Ford mechanic's trick)

[Mitch]

can't you use throttle body cleaner? I heard it will make the engine run like $#!& the moment it hits a leaky area.

[carnuck]

yup. Almost anything will work