This is on my 1997 S10 pickup.

I just replaced the front rotors and pads (~3 weeks ago?), and the brakes seemed a little "odd"... Maybe spongy, but still stopped okay... I haven't replaced the calipers...

Then I noticed a hissing noise coming from under the dash when I was pressing the brake pedal. Once pressed fully, I no longer here the hissing.

I did NOT notice any affect on idle quality, so I thought maybe it was something I never noticed before...

I rarely drive the truck, and just the past few days I noticed the brakes feel a little different. Still stop fine, and doesn't seem like the power assist is completely gone, BUT, When I put the truck in gear (automatic), it will almost lurch forward a little bit, and I have to press harder on the pedal to stop the truck (It doesn't continue, so I don't think its the master cylinder leaking)...

Its odd, because right before the pads/rotors, it seemed fine, but right after, it seemed "wierd"...

Does this sound like the Booster is going bad (or gone?)?

If so, I'll replace it, and maybe the master (loaded booster?) along with the calipers/hoses...

Thanks

PS, I "searched" and I read this recent thread, and sounds pretty close to my symptoms:
http://www.chevelles.com/forums/showthread.php?t=233819&highlight=bad+booster

Sounds pretty close to what mine was doing. I have a 97 S10 Blazer zr2. Brake pedal was real weird. Also motor acting up like a bad vacuum leak. I let it go fro a while till I had almost no assist (dangerous). I replaced the booster for about $90 and a slightly bruised up ribcage from workin under the dash. If you take it to a dealer, $650. I didnt disconnect the brake lines. Just unbolted and moved the antilock brake mechanism and then unbolted the master from the booster. No need to disconnect any hydraulic lines, unless of course you replace the master. My Blazer had about 155000 when the booster went south.

Mine has about 115,000 miles...

A few months ago, I was debating selling it and getting something bigger (I could use something that will hold 4 people), but I decided to keep it, and consequently spent about $1200+ on tires/shocks/alignment/rotors/pads/fuel filter/trans filter/oil change/plugs/wires/cap/rotor... Been thinking about calipers and brake hoses (it was "pulling" a bit to one side after new pads and rotors)...

So I guess I might as well pony-up for a new booster...

$73 or $183 with a master cylinder... with my luck, if I change just the booster, the master will go out...

DOH!

I been dumping some money in my Blazer too. Although its 11 years old and 170000 miles on the odometer, the 4.3 still runs like new. Looks great too. No rust. Averages around 19-20 mpg too. I plan on driving it as long as I can. No car payments for me. I'd rather sink a grand into it a year rather than make 3 grand a year in new car payments.
If you do that booster, have a Chiropractor on call. Then again I'm 48. LOL

I'd rather sink a grand into it a year rather than make 3 grand a year in new car payments.
If you do that booster, have a Chiropractor on call. Then again I'm 48. LOL

My dilemna is that mine has the 3rd door and bucket seats, so I can only carry 3 people. due to my kids size (4 and 6 yrs old), they can't ride in the rear jump seat...

BUT, I'm not ready for more payments either...

I held the brake pedal firmly (with my foot), and it doesn't continue to drop, so I am assuming the master cylinder is okay...

With the truck turned "off", the pedal is very high and stiff (no assist)... as soon as it starts, the pedal drops way down (almost the floor, but not quite)...

ya, that sounds like the same symptoms my Blazer had. The master is still good with 170000 on it. I dont remember how I definitely came to the conclusion that the booster was bad. Just the brakes sucked and the motor was running kinda bad at low speed like a surging and almost stalling like a bad vacuum leak.

I did notice a slight surve when I stabbed the pedal forcefully, but otherwise, seems to run fine...

Thanks,

I guess I'll go order a booster...

Hopefully thats it!! let me know. the dealer pays 3.5 hrs to do that job. It took me about that amount of time but, spread out over 2 days! LOL My back and ribcage did appreciate taking off the four nuts under the dash! I'm 6'3 230 so that made it a bit tough gettin in there. I almost took out the drivers seat to maybe make it easier. good luck!

Yeah, those 4 nuts were a little hard to get too... Also had to pull the air intake tube and move the air cleaner box to slide the ABS stuff forward...

Still only took me maybe 3 hours, not working very hard (but over 2 days...

It was supposed to be something like 105 today, and the truck is parked outside... Instant sweat when I started putting the stuff back together...

that lower right nut was a B!tc#...
And of course, getting the upper right nut on the stud...

But everything went smoothly, and it seems to have solved the problem... Stops well...

Thanks

in my car i would put it in nuetral at a light an pump the brake pedal an the idle would come up a lil bit. does this mean the booster's bad? just re-did front my suspension. i just removed the master an TIRED the booster sure is a pain. only got the upper left bolt loose.

Yeah, those 4 nuts were a little hard to get too... Also had to pull the air intake tube and move the air cleaner box to slide the ABS stuff forward...

Still only took me maybe 3 hours, not working very hard (but over 2 days...

It was supposed to be something like 105 today, and the truck is parked outside... Instant sweat when I started putting the stuff back together...

that lower right nut was a B!tc#...
And of course, getting the upper right nut on the stud...

But everything went smoothly, and it seems to have solved the problem... Stops well...

Thanks

Glad to hear problem solved! Sounds like you did it exacty the way I did. Just sliding everything out of the way. It was only about 90 when I did mine though with about 80% humidity, so ya, a sweaty job indeed. I do remember that lower nut being a p.i.t.a. I remember just thinking to myself "if somebody else can do it, I can!" You gotta have the right tools, thats for sure.
Bet your glad you didnt buy the master!