i have a 94 ford ranger 4.0 and i have a vacuum leak, but i dont know exactly were it is, for a while, i had a vaccuum cap missing, and i always that was what was making hte hissing noise, but now i have the correct cap on it, ( i have a 7/32 on it) and it still hisses, when you shut it off, then it is real obvious, you can hear the last suck in of the air, and i was wondering were the best place to look for the leak is, and how exactly to find it,
any help?
quack!

 

A couple of ideas, especially for a leak that big.
1) Get a stethoscope or similar device and use it to listen to various vacuum lines/parts. You should be able to hear a leak that large.
2) Get a propane torch or similar. Squirt propane near vacuum lines/connections. The leak will be located where the propane getting sucked into the intake causes the idle to increase.

 

but where should i start, i dont know exactly were all of the vaccuums are, how do i know that it is a vacuum??

 

There should be a sticker under the hood with a schematic of the basic vacuum operated accesories. I would start with the hoses (and accompanying accessories) that come off of the vacuum tree near the rear of the upper intake manifold. Not certain on a '94, but on my '92 that includes
brake booster
cruise control
fuel pressure regulator
automatic transmission modulator
airbox control valve
vacuum reservoir
ventilation controls.
PCV attaches to the upper intake just forward of the vacuum tree
On a '94 there should be vacuum hoses to the EGR system (no EGR on '92 so I'm not familiar with how they set it up)
finally a hose that attaches to the throttle body for the evaporative emmissions system.
And, while your inspecting the vacuum tree, there may be more ports than you have hoses/accessories. Normally it's capped off, but it seems common to lose a cap off of the tree.

 

wow thanks, that really helps alot. i will have to take a look at all of that stuff this weekend!!!
quack

 

well just thought i would tell you guys, i foudn the leak, it was right by the other leak, it was on the other side of it, i didnt see it there, and i just looked and i was like wow theres the leak! and i just capped it off w/ a 7/32 inch cap and bam the noise stopped i was releaved!
thanks for the help!