91 explorer phantom vacuum leak

[darkarrow]

i have a 91 EB explorer and i dont know where my vacuum leak is coming from. the sound originates behind the vacuum tree area on the driver side of the intake manifold. i have replaced many hoses and checked many for leaks, but i havent found any yet. if anyone knows of an odd place where there may be a vacuum leak in this area, please help me find the problem, any help is greatly appreciated.

 

[Rhett]

It's very difficult to diagnose from what you've posted. How do you know it's a vacuum leak? Perhaps the IAC is noisy. Do you have any of the symptoms of a vacuum leak in the driving condition of the vehicle?

 

[pinoyesv6]

there's an extra nipple on the back of the vacuum tree. it doesn't have a hose going to it but usually there's a cap. the cap fell off of mine and thats when i got the leak. i just plugged it up with a hose i tied into a knot and the problem went away.

 

[Longjohn119]

Squirt a little oil around the seams (gaskets) of the intake manifold with the motor running ... the oil will temporarily seal any leak and the RPMs will jump a little and then fall back as the oil sucks through and the leak becomes active again ... if nothing happens then the gaskets is probably alright and the leak is elsewhere ... this motor is known for blowing intake gaskets and this is the best way I know of to find out

 

[Mr. Stroker]

this is a bit dangerous and not the best way but the old guy down the street from me uses a propane tank(not lit) and when u get a leak it sucks in the propane and drops the idle.

its not the best way but it is effective so try at your own risk

 

[jreece04]

I have heard of using carb cleaner and spraying it around the engine compartment and you are supposed to see an increased idle if it hits a leak. it seems more safe then propane and is pretty cheap.

 

[91Expgeek]

there's an extra nipple on the back of the vacuum tree. it doesn't have a hose going to it but usually there's a cap. the cap fell off of mine and thats when i got the leak. i just plugged it up with a hose i tied into a knot and the problem went away.

Same thing just happened to me - with the engine running (and the wife keeping it running) located the vacuum leak on the back of the little octopus (vacuum tree) with my finger - plugged it with my finger and idle went to normal and vacuum leak sound quit. That "extra cap" was missing. Replaced it with a rubber cap from my "rubber junk" drawer (I've got *lots* of junk drawers) and the problem was solved. Hope this helps somebody else. -=dave=-