87 F150 5.l V8Just as title says, brake booster? Any ideas? Thanks for the help. Also, any idea on this line? New to this truck. Thanks all.

 

Don't jump to the conclusion that its brake booster yet... Your truck has VACUUM operated cruise control, right? For those systems, there is a vacuum dump valve by the brake pedal. It's purpose is to be a safety when cruise is engaged, if for some reason the electrical didn't shut off cruise when braking. Wouldn't think there would be vacuum there if cruise is OFF, but it's been a while since I had a Ford vehicle with vacuum-operated cruise. All mine now are electrically-operated, the motor kind, where a motor provides the muscle to pull throttle linkage, not vacuum on a diaphragm.

 

Hadn't thought of that. I'll check the cruise control, I'd say it emanates more from behind the dash cluster than brake pedal area. I'll have a listen today

 

Are you having to pump the brake pedal, when you start stopping, as in does it go to floor the first time you apply brake pedal? If you have your foot on brake and truck in gear, does brake pedal start easing to floor, before you take foot off brake.

 

Nope, brakes are great, just redone. Noise was present before having brakes worked on as well.
Noise is present when I start the truck, goes away when I brake and comes back when I let off.

 

Bet it's the vacuum dump valve for the cruise, it doesn't close properly when you're off the brakes and the airflow causes the sucking noise. Then when you step on the pedal the valve goes wide open and dumps all vacuum and the hissing stops. Look at your brake pedal, the valve is slightly above the BOO (Brakes-On-Off) switch, it has a threaded body with a little plunger coming out its front and coming into contact with a plastic pad on the brake pedal arm - try wiggling the body so its threaded section gets real close to the pedal arm pad but without physically touching it. You don't actually need to rotate the valve even tho it's got threads as it's just little spring-steel fingers keeping it in place and not proper thread cut into the mounting bracket.

 

Thanks, I'll check this when I get to work on the truck later, let ya know how it goes.

 

So, leak is coming from the seal on the brake pedal plunger into the brake booster as pictured.
checked the cruise control switch and backed it out as above. Brakes are great right now, so just a minor annoyance I can live with unless it's an easy fix which it don't seem like it is

 

Sorry bud, ain't an easy fix that, you'll need a new booster eventually. Just keep an eye on how the brakes work, when you start feeling having to push the pedal harder (not the same as further down, that's different) that's your booster losing its ability to properly assist you and calling for a replacement. Do you by any chance tow anything with this truck?

 

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that is about what I figured initially.
This truck is officially retired recreational vehicle, I'll keep an eye on the brakes and put this on my list. Thanks for the heads up

 

Mine has been hissing when I apply the brakes for probably well over 10 years now. Keep thinking I will change it next year. But, it's been so many next years, I'm about too old to want to mess with it.

 

Seems easy enough to replace the booster, I'll just grab one and chuck it in there.

 

It probably is fairly easy. But, I've kept putting it off until now I'm old and arthritic. It's hard enough getting into the truck these days,,,lol

 

Fingers crossed I've got a few more years before the thritis gets me. I feel for you older fellas workin in tight spots, let that booster whistle!