More Vacuum problems... | Ford Explorer Forums - Serious Explorations

  • Register Today It's free!

More Vacuum problems...


Active Member
June 3, 2009
Reaction score
City, State
St. Albert, Alberta
Year, Model & Trim Level
'92 XLT
Well last night I was out driving...truck working perfectly except for useless Auto hubs lol. This morning I get in and fire it up, at first I notice a very loud hissing sound and second I'm getting a bad idle. I popped the hood and found the vacuum line that I BELIEVE is the problem.

This is the hose on the vacuum tree. Its the black hose.



I checked all the hoses and the vacuum valve check (The black and white connecter between the 2 hoses). Everything seems good but there's no change. Next I fired the truck up, took off the hose from the tree and put my finger against the opening on the tree (second picture). It steadied the idle but only temporarily.

So I searched on the forums and I found out that hose goes to...I think..the brake booster? Also many similar problems also had braking problems. I took my truck for a spin around the block. From 500 - 1000 rpm its rough. After that the hissing goes away and it runs perfect. Also my brakes work perfect. I'm thinking maybe my brake booster is broken or stuck? If thats possible lol.

I'm pretty positive this is the hose that's giving me problems. The lines are all good, but its just not getting air like theres a block in the booster. What shall I try next? Also how hard is it to take off the booster and disassemble it?

Join the Elite Explorers for $20 each year.
Elite Explorer members see no advertisements, no banner ads, no double underlined links,.
Add an avatar, upload photo attachments, and more!

The nice black looking hose that has the plastic thing in-line is your cruise control.

The brake booster hose is the dirty one right next to it.

Your brake booster or booster hose fitting (one way valve) may be having an issue and causing a hiss, but that wont' cause the hose for the cruise to come off..

See if you can find where the hiss is actually coming from as a vacuum leak will mess with the engine/computer...

If you can't find it by ear.. spray a little carb cleaner where connections are and see if the idle changes.. If it does, you found the leak..

Also, double check there are no other open ports on that vacuum octopus. A few of them should be capped off and if the one for the cruise blew off, maybe one of the caps came off too...

Okay thanks. I'm almost certain there no open ports. I was looking and it looks like none are even capped off?

And now that I think about it, when I first found the hissing I THOUGHT the black hose had a hose clamp around it, I don't think it ever blew off.

The hissing is coming from the ?grommet? on the vacuum tree where the black hose attaches. How likely is it that my vacuum tree has a crack in it or the grommet all of a sudden broke?

And for future reference, if that drum like thing the black hose connects to isn't the brake booster...what is it? lol

Yup, those capped vacuum ports on the back side will always getcha!:thumbsup:

And for future reference, if that drum like thing the black hose connects to isn't the brake booster...what is it? lol

the brake booster is the thing with the dirty hose connected to the firewall.. There is a 1 way valve on the brake booster which can sometimes go bad (gromet) and leak.. thats what I was thinking might have been your issue..

The clean "black" hose in your pic connects to the vacuum canister for the cruise control. It uses vacuum to pull the throttle cable when it wants to go faster.


My Son's Ranger started making a vibration noise. It is coming from the vaccum line from the manifold to the Cruise control diaphram on the drivers side fender (same one you were reffering too). Everything that uses a vaccum seems to work, the cruise will spit and sputter a touch, but never shuts off. The line really vibrates and is loud and the truck really runs (idles) rough. I don't see a leak.

Mud4Life- was your situation similar? Where was the port that wasn't capped off? I'll check that too.

It was almost similar. The port was directly on the backside of the vacuum tree. It was pointed towards the firewall. And if you KNOW its coming from the hose that connects your cruise control then its probably not the same as I had. If the line vibrates maybe it has a small hole in it? I just took it off and blew air through it while plugging one end and slowly checking the entire line.

i got a ? please help anyone need my car fix before thurday because i'm moving so please help and tell me so i can buy it from autozone...mine is like this having same prombles...but see my hose broke off to the back one What's It Go To And Would It Mess It Up If I Blocked It Off Because Can't Afford For My 1994 Ford Explorer XLT To Have Anymore Promble's.But Really What To Know What Does It Go To... This Look For The Red I Did To The Pic Thank's And Mud4Life I Used You'r Pic Just To Show!!!!

Are you sure the hose broke off? Some of them are just plugged from factory. The hose can be bought at any store really. Even just some cheap hosing from a hardware store can work. I don't have my Ford anymore so I can't tell u where the hose goes. But if its the same as mine, just plug it with something.

hehehe.... Fixed it.... :confused: There was a capped port hidden on the backside of the vacuum tree.... Easy fix at least lol. Thanks for the help :thumbsup:

Lol, first problem I ever had was a capped port coming off... I paid 65 dollars at a shop for someone to fix it. After that was when I originally started learning myself. Happens to the best of us I suppose LOL

yea im sure it broke off because i was trying to put it back on and it broke on me...

simple, as long as all you broke was the hard plastic line on that vacuum just slip a short piece of 1/8" vacuum hose over the broken pieces until you feel like replacing it.

hehehe.... Fixed it.... :confused: There was a capped port hidden on the backside of the vacuum tree.... Easy fix at least lol. Thanks for the help :thumbsup:

I'm glad I read through all te posts.. I was going to ask you to look to the very Firewall. There is a hidden one there.

Glad you got it

i got a 1994 Ford Explorer Xlt And For Some reason my oil GAUGE is almost on the (L) but say's that way wen driving it this did not start happing until i let my sister use it last night and she hit a deer but never hurt anythang besides the front grill...can anyone help me??? it just wont move at all idk what the deal is well it dont look like its moving...