brake Booster questions

[Haus]

I think my brake booster is bad. I hear a constant hissing/swooshing under my dash and my car is very hard to stop. and my hvac controls are off

any info on how to replace it?

1992 LX 5.0

 

[Mustang5L5]

Well, first check the 1 way valve and grommet on the booster first under the hood. Usually they fail first. Remove the one way and verify it only flows from the booster and not in. Check the grommet to see if it's dry rotted.

 

[Haus]

i tried but seems im gonna have to remove the master cyl to beable to remove the 1 way valve/grommet to check it?

Just so i know but is that gonna cause a mess or have to bleed my brakes if unbolt the master cyl

 

[Mustang5L5]

No, you don't need to remove the MC (it doesn't mess up the brakes to unbolt it anyway)

The 1 way valve is the plastic valve the vacuum line connects to...also called the booster check valve

Make sure there are no leaks here

 

[4rdnut]

some cars when you bolt the master cylinder on it presses on the one way valve just slightly by the reservoir, like my car, preventing it from being removed easily, just unbolt the master cylinder and see if this will give you room to remove the one way valve.

 

[Haus]

yeah theres no way of taking off the check valve with out taking off the master cyl. not enough room to pull it out.

so i can remove the master cyl and there will be no problems?

Ill try that and check the valve and get back to ya

 

[Mustang5L5]

Ah, i haven't looked at a stock fox booster in some time. I'm used to the larger SN95 booster.

Yes, you can unbolt the MC and pull it forward a bit without messing up anything with the brakes. The booster rod sticks out and pressed against the MC bore. Just don't turn the booster rod any and you'll be fine.

You may not need to remove however. Visually inspect and wiggle it and listen for a hiss or sign of leak. However, if the rubber grommet looked cracked, it more than likely is leaking.

Autozone sells replacments

 

[Haus]

i only hear the hissing inside the car under the dash. makes me think the booster is shot i guess. but i will check the grommet and valve. grommet does feel like rubber and not hard and brittle

 

[Mustang5L5]

Starting to sound like a faulty booster...I'd try and diagnose a bit more. Hate to tell you to replace a booster...not a quick job, but manageable.

When does it hiss? When you hitmpedal...or all the time?

 

[Haus]

all the time. as soon as i start the car until i turn off the car

 

[Mustang5L5]

Well, thats not normal. It's a vacuum leak.

If you take some carb cleaner and carefully spray itnaround, you might be able to locate the leak if the idle raises up

 

[Haus]

so your saying its not possible for the booster to make that hissing sound?

the braking sucks unless i put it in neutral to help me slow down

 

[Haus]

no hissing sound at all behind the dash when i disconnect the brake booster hose from the BB under the engine.

so what does this tell me?

 

[Mustang5L5]

Sounds like booster leak to me