maybe its me but i just noticed over the last couple of days when i push the brake it seems a little hard to push down and when i do there is this hissing noise? what is that?
Is the hissing noise bad?
also if i push it down a little the hiss will just keep coming out. what is this? also i know my rear drums are shot i hear the griding in the back would this have anything to do with my brakes being hard or the hissing? what should i look for or what should i fix to stop the hissing?

 

It sounds like your vaccuum line on your master cylinder is leaking. It's about 3/8 to 5/8 inside diameter connected from the intake manifold to the front of the black drum shaped object behind where you put brake fluid in. IF you can't replace it immediately, wrap it really well with black tape. That will be a temporary fix until you can get to a parts store and replace it.



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Chris G
91 TA WS6


See more of her here!
Wise man once say "Red ones go faster!"

 

It's not a hose leak. Your vaccum booster is shot. You'll have to replace it. There's a rubber diaphragm or something in there that can fail. When you push on the brakes, the failed diaphragm creates a vacuum leak. That's the hissing and the resultant hard pedal insues because you have effectively no vacuum assistance on your brake sytem now. It happened to me.

The fix isn't fun but it's doable. you've gotta remove the master cylinder (remove the brake lines and unbolt it). Then crawl under the dash (this is the "no fun" part) and remove the 4 nuts that holt the brake booster on the firewall (15 mm wrench IIRC). These are the same nuts/bolts that secure the pedals to the firewall. You've gotta disconnect the pushrod and stuff too.

Don't loose the little pushrod that goes between the master cylinder and the booster.

HTH
Clem

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Clem
SCCA TransAm Series Race Mechanic/CrewChief
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1983 Z28 with LG4, 5 speed, and (unfortunately) T-tops
1983 Z28, NO T-tops, (unfortunately) Auto Transmission (hopefully not for long)

 

Clem is right, it's the booster. But I would caution you to look very carefully at the master cylinder; the most common cause of booster failure is brake fluid leaking out the back of the MC and dissolving the diaphragm. If your booster is rusty right below where the MC attaches but no where else, then you you need a MC too. If it's bad and you leave it there, it will ruin your new booster too.

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"So many Mustangs, so little time..."
ICON Motorsports

 

well is it safe to drive around?? are my brakes gonna not work one time? i call a shop and i can't get into next wed. so will i be ok driving to work for 2 days??? how much is a booster to?

 

if it was the master cyclinder wouldn't my pedal go to the floor?

 

I know this article was written a long time ago, but I was wondering if you could give me some advice. My brakes are having the exact same problems as yours did. They are really hard to press down to apply brakes just at a normal deceleration and they hiss and the idle jumps when applying brakes at a red light to stay still. How did you fix your brakes? Did you take them to a shop? And what exactly was the problem? I think it is my brake booster that is messed up also. Thanks in advance for any responses.

Will

 

You just replace the brake booster. It's not real hard or anything; 4 nuts in the interior of the car on the firewall, and 2 nuts that hold the master cyl to it.

Like I mentioned above, about 90% of the time, the reason they go bad is from brake fluid leaking into them from the MC. Check it carefully; otherwise you'll just ruin a new one too.

 

So it's not too hard to do? I've been slowly learning to do things on my car.... I called just to get a rough estimate for a new brake booster installed, they want $297 plus tax. I think I will look on ebay or through the classified on this site for a used one. As far as install goes: any special tools needed or any extra advice? Also how long does it usually take? When buying a used one.. is there anything I should look out for? Thanks for your help.

Will

 

The only thing you should look for in a used one, is to get a new one instead.

You need either a 13 mm or 15mm deep-well socket for the interior nuts, can't remember for sure; the nuts for the MC are 15mm.

 

So if I have to buy a new booster, do you know of any places where I can get one for a reasonable price? I am on a really tight budget. Also, what exactly should I look for when looking at the MC? Thanks for all of your advice.

Will

 

I have a question on brakes too. Occasionaly I have to pump mine to get them to apply forcefuly. And if I must push down in an emergancy, it would suck when I push and it just smooshes.

 

Lessk, does it make a air sound when you push down?