Recently I have noticed on my 2003 Expedition (5.4, No Mods) that there is air hissing/leaking in through the brake pedal area. I have not touched anything but if I put the slightest pressure on the pedal when braking, it stops completely, but as soon my foot is off it will go make to making the noise of air leaking back in? Does anybody know what I can look at, I have the ford Certified Pre-owned Warranty and that is comprehensive for another week or so, so I would like to get it checked out and fixed.

Thanks Matt

 

It's either the brake booster under the hood, or it's the cruise control vacuum release switch down near the pedal.

 

Well I took a look at it while it was running and making the noise... it is the actual (green arrow pointing) thing? I dont know what that is called?
<a href="http://www.flickr.com/photos/24020690@N07/2750654073/" title="0810081744 by matkt1108, on Flickr"><img src="http://farm4.static.flickr.com/3207/2750654073_ebe14e0338_m.jpg" width="240" height="180" alt="0810081744" /></a>

 

That's the backside of the brake booster. It's not the actual brake booster that you see there, the booster is just on the other side of the firewall from your green arrow.

 

So then what are we thinking... The brake booster is bad? or is it the spring looking thing my arrow is pointing to? I know that the brake booster is the big Round thing under the hood that the master cylinder is connected to. and can the spring looking thing go bad? or is that all one piece of the brake booster?

Actually as I look here it looks like it is the brake booster? I am def gonna get this fixed, but what should I be worried about?

 

It probably the seal around the shaft that's leaking. It's being hidden by that "spring looking thing." Maybe you'll get lucky enough and get away with just being able to change the seal instead of the whole booster. But the boosters are sealed up pretty good and it's more than likely that you will have to replace the whole thing.

 

Well thats ok because I bought the Expedition less then 3 months ago and got the Ford Certified Pre Owned warranty which is pretty much comprehensive. And I found this....
https://www.ford-trucks.com/forums/6...nder-dash.html

So I will call the dealership tomorrow and have them change the booster, as long as it's covered why not!

 

That's a no-brainer right there. Now git 'er done!

 

Thanks for the help! will let you know later today on how it went at the dealership.

 

It is the Brake Master Cylinder. It will make a hissing or "squishing" noise.

 

Wrong... it is the Brake Booster and was changed out and everything is all good now... for $100 (deductible) why not, part is more than that and labor too.

 

My 2003 Expedition is now doing the same thing. Has anyone called a dealership and ask them why these are going bad? I have had a few Fords a lot older than this and never had this problem before except with my 1972 Mustang and that one was 20 years old. Maybe the new boosters are made in Chinaa.

 

holy crap. It's an epidemic. Mine just went yesterday. '03 Expy.

$99.99 at NAPA (plus core). Now I have to see if it's doable (by me).

 

I reached under the dashboard and jiggled the rubber boot (actually twisted it) and the hissing would stop for a while.

Couldn't it be that the rubber boot just needs to be glued down? It seems to sit around a metal lip but it won't stay seated on it...

???

 

where is the vacuum release switch located
I just replaced the brake switch and discovered my cruise control not working and now I hear air when I drive but it stops when I break