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yes it is the power brake booster...do you hear alot of air coming from under the brake pedal? im having the same problem..my brakes are real hard and can hardly stop..got to push them real hard..there is NO power there what so ever..im replacing the brake booster this sunday. now im not sure if a 4th gen booster will work or not cant help you there..maybe someone else can answer that.
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yes it is the power brake booster...do you hear alot of air coming from under the brake pedal? im having the same problem..my brakes are real hard and can hardly stop..got to push them real hard..there is NO power there what so ever..im replacing the brake booster this sunday. now im not sure if a 4th gen booster will work or not cant help you there..maybe someone else can answer that.
cool, though i can stop, but i cant lock the wheels up anymore.
the 4th gen pedal will work in our cars, so i see no reason why the booster wont.
I had a 4th gen booster bad when i did my engine swap, and decided to put the 3rd gen one back in and trashed the 4th gen one....stupid me
I would do a vacuum test frist on then booster and check if it leaks down.What pedals do you have in the car? I dont know the geometry of the 4th gen pedals but if the lenth is different it will defentley change the amount of force applied to the hydraulic system.
I would do a vacuum test frist on then booster and check if it leaks down.What pedals do you have in the car? I dont know the geometry of the 4th gen pedals but if the lenth is different it will defentley change the amount of force applied to the hydraulic system.
im using 3rd gen pedals, the 4th gen reference was just for bolt spacing.
well, i did a vacuum tst on the booster. I was able to get the gauge to 19.5 inches of vacuum and it stayed and didnt drop. So this is telling my that its ok?
Only thing i noticed was that the hose connected to the vacuum port on the booster was not clamped and was a little loose. Maybe it was leaking?
Next time i take the car out i'll see if there was any difference
If the booster it self holds vacuum then dont forget to check the check valve (one way valve),and see if it hold vacuum too.Plus the rubber grommet can also have a leak. Some times the diafram in the booster will get week from just wear and tear,old age.
Well if the hose was loose then you may not have bin geting enough vacuum to the booster and it would explain why the pedal gets hard at 1" to 2" of pedal travel.Like when the booster is full of vacuum when u first shut the engine and you press the pedal,each time it gets harder and harder untill its empty.But if the hose was leaking the engine would be running lean,maybe even pin.I would check the plugs to varify.
i have the opposite problem my peddle is so soft i can floor it and they wont lock up is that also the booster? i dont own a vac gague maby ill buy one today. what am i looking for as far as vac?
stock front (for now)LT1 rear with 3rd gen prop valve
i have the opposite problem my peddle is so soft i can floor it and they wont lock up is that also the booster? i dont own a vac gague maby ill buy one today. what am i looking for as far as vac?
stock front (for now)LT1 rear with 3rd gen prop valve
That's more likely air in the lines or a bad master cylinder.
flynbuy is going to make a small (not really small) fortune off me this week ill upgrade and let you guys know how it goes thanks for the quick replys!
I am having a similar problem and also wonder if it is my brake booster. If i hit the brake once it seems fine, the brake pedal travels normal distance but if i pump the brake pedal it gets hard and becomes difficult to stop. If i give it a few seconds though and then slowly apply pressure to the brakes the pedal will travel normal distance. any ideas?
I am having a similar problem and also wonder if it is my brake booster. If i hit the brake once it seems fine, the brake pedal travels normal distance but if i pump the brake pedal it gets hard and becomes difficult to stop. If i give it a few seconds though and then slowly apply pressure to the brakes the pedal will travel normal distance. any ideas?
That sounds like the booster or low vacuum. What is your vacuum at idle?
an easy way to test your booster, without a gauge,
1.with the car off, pump the brake pedal til the brakes are hard to push.
2.with your foot still on the brake (with the brake still being hard to push) start the car, you should feel the booster engage.
if it does, your booster is working correctly, as for leaking or not,
1. take your foot off the brake, turn off the car.
2. let the car sit a minute, then push the brake, is it hard to push? it shouldn't be until depressed two or three times, getting progresssivly firmer
things to check
check the "check" valve that the vacuum line going to your booster hooks to, air should not move both ways though it, you should be able to suck air through it, but not blow it out. if you can, replace the valve, retest the system. if it still doesn't work, it's prob the booster.
an easy way to test your booster, without a gauge,
1.with the car off, pump the brake pedal til the brakes are hard to push.
2.with your foot still on the brake (with the brake still being hard to push) start the car, you should feel the booster engage.
if it does, your booster is working correctly, as for leaking or not,
1. take your foot off the brake, turn off the car.
2. let the car sit a minute, then push the brake, is it hard to push? it shouldn't be until depressed two or three times, getting progresssivly firmer
things to check
check the "check" valve that the vacuum line going to your booster hooks to, air should not move both ways though it, you should be able to suck air through it, but not blow it out. if you can, replace the valve, retest the system. if it still doesn't work, it's prob the booster.
what do you mean "feel the booster engage" kick back like my 04 seirra dose or fall to the floor like my camaro?
could be the master bleeding pressure off.
replace both and call it a day.
brakes get annoying when trying to track down an issue.
get rid of it all and be done with it, IMO.
__________________ 1988 IROC-z/28. 4th gen interior. 408 LSx
sporting the stock fuse box and taillights.
too many mods to type.
6.23@109.71 pump gas. all motor.
well, im still screwing with this. Replaced the master, it was leaking anyway. Re plumbed things, installed a adjustable prop valve and gutted, cut, and welded the prop valve into just a junction block for the front brakes, removing the rear section entirely.
Brakes are exactly the same as before.
IT has to be the booster, everything else is new, and the calipers bleed and function properly.
The booster does hold vacuum without issues, but something isnt right. With the master removed, the brake pedal will travel all the way to the floor with slight resistance. Once the master is installed, with the engine running or not, the pedal moves about 1" to 1.5" and stops dead, i can stand on it and the firewall just bends and nothing else, the brakes blow.
Im going to have to pickup a new booster, unless there is something else to check.
to put an end to this sage once and for all, the issue was a leaky vacuum hose from the carb to the booster. I removed all the hoses and my auxiliary vacuum canister, ran a new short piece of hose from the carb to the booster and now i have brakes! Probably should have tried that a while ago, but everything is pretty new so i assumed the hoses were fine.
But im glad i did all the work, the new master looks really good, no more yellowed reservoir, it doesn't leak like the old one, and the adjustable prop valve for the rears is great. I need a lot or rear brake because of the massive steamrollers i have back there and the adjustment helps, stock bias just wasnt cutting it.
Instead of replacing the booster with a stock vacuum booster, why not get a hydraulic brake booster? It'll finally make power steering a great feature to have.
because what i have works very well now, and hydroboost is a ugly mess of hoses. And from what i hear, you dont get a very good pedal feels from hydroboost.
Also, i dont like the idea of running the brakes and the steering off the same pump. If the belt brakes, you lose steering and brakes. I would rather loose my brakes and be able to steer, or lose my steering and be able to stop than loose everything at once.
__________________ "i thought the plan was fool proof?"
"fool proof, yes. idiot proof, no."
where did you pick up a new booster and master cylinder?
You can get a re-manufactured 82-92 booster for under $100 from autozone. You can get a re-manufactured 82-92 master cylinder for under $30 from autozone. Re-manufactured is basically all new parts in an old core. If I would have known they were this cheap (and easy to replace), I would have replaced them in both of my thirdgens years ago even if they weren't completely shot.
Didnt want to start a new thread yet, so I'll ask here.
Quote:
yes it is the power brake booster...do you hear alot of air coming from under the brake pedal?
I have a loud hissing sound, like air blowing out under my pedal when I press it.
I have C5 fronts and LS1 rears with stock 89 J65 disk brake proportioning valve and master/booster combo. All stock there.
I have no brakes. Car has good vacuum, the motor is not wild. Used to be ok stopping with stock front disks. Only thing I changed was C5 fronts. Bled the brakes good 2 times and still have no brakes. Wondering if my booster is bad.
I have similar conditions as above. Hard pedal. Does not travel down very far. Hard to stop the car. 30mph and it takes a good bit of distance to stop. Definately not safe.
Check valve is working, air cant blow in from the turbo boost but can open up under engine vacuum. I did not do a vacuum test however, not sure how to do that. Did notice it did not hold vacuum over night. Will try again however.
I did try pumping brakes with engine off to get all the vacuum out. Then while holding the pedal down hard, i started the car and it depressed just a little bit but I had alot of pressure on the pedal. Definately doesnt feel like it used to.
Any ideas? Do I need a different master and proportioning valve for this setup? Booster possibly bad now from alll the turbo downpipe heat?
Didnt want to start a new thread yet, so I'll ask here.
I have a loud hissing sound, like air blowing out under my pedal when I press it.
I have C5 fronts and LS1 rears with stock 89 J65 disk brake proportioning valve and master/booster combo. All stock there.
I have no brakes. Car has good vacuum, the motor is not wild. Used to be ok stopping with stock front disks. Only thing I changed was C5 fronts. Bled the brakes good 2 times and still have no brakes. Wondering if my booster is bad.
I have similar conditions as above. Hard pedal. Does not travel down very far. Hard to stop the car. 30mph and it takes a good bit of distance to stop. Definately not safe.
Check valve is working, air cant blow in from the turbo boost but can open up under engine vacuum. I did not do a vacuum test however, not sure how to do that. Did notice it did not hold vacuum over night. Will try again however.
I did try pumping brakes with engine off to get all the vacuum out. Then while holding the pedal down hard, i started the car and it depressed just a little bit but I had alot of pressure on the pedal. Definately doesnt feel like it used to.
Any ideas? Do I need a different master and proportioning valve for this setup? Booster possibly bad now from alll the turbo downpipe heat?
sounds exactly like the problem i had, a vacuum leak between the booster and the intake/throttlebody/whatever.
the booster does make a woosh noise when you push the pedal, i think if the booster is bad, the pedal will just hit the floor.
vacuum line checks out. booster was pumped to 10 inch Hg with a little hand pump and it holds. I pressed pedal down one time and it dropped to 5. I guess its normal. So I assume the booster is working but the brakes are not. Hose is not leaking. I tested it. Its not a small hose either. Check valve works fine.
What else could it be if the brakes have been bleed right and still dont improve? Do C5/LS1 rear combos need a different master? Am I not getting enough pressure to the caliper?
Leave the one way valve on but put a T on it in between the valve and the booster then put a guage on it, then use a vacuum pump or the engine to apply vacuum to the booster shut the engine off or if you use a vacuum pump disconect it make sure u put at least 14 hg on it then let it sit it should hold overnite if not you have a leak if it holds then press the pedal it should be soft if not then the diafram in the booster is weak and you'll need a new booster
vacuum line checks out. booster was pumped to 10 inch Hg with a little hand pump and it holds. I pressed pedal down one time and it dropped to 5. I guess its normal. So I assume the booster is working but the brakes are not. Hose is not leaking. I tested it. Its not a small hose either. Check valve works fine.
What else could it be if the brakes have been bleed right and still dont improve? Do C5/LS1 rear combos need a different master? Am I not getting enough pressure to the caliper?
From what I gather you changed the front 10.5" discs & iron calipers to 13" (?) discs and C5 calipers. Both of these calipers have 5 sq/in of piston area. So there isn't any difference in clamping ability.
The larger C5 rotor will increase brake leverage, providing more braking power.
The wild card in this is the brake pads. Are they decent/good pads, and more importantly, are they bedded in. With some pads it can take quite a while for them to get bedded to the rotors. And if they get glazed in the mean time, then need to start over getting them bedded (sand off pad face and re-install).
From what I gather you changed the front 10.5" discs & iron calipers to 13" (?) discs and C5 calipers. Both of these calipers have 5 sq/in of piston area. So there isn't any difference in clamping ability.
The larger C5 rotor will increase brake leverage, providing more braking power.
The wild card in this is the brake pads. Are they decent/good pads, and more importantly, are they bedded in. With some pads it can take quite a while for them to get bedded to the rotors. And if they get glazed in the mean time, then need to start over getting them bedded (sand off pad face and re-install).
RBob.
I have hawks hps pads up front. Just installed them and did some light driving but noticed they did not seem to stop so I stopped driving. I don't really see much signs of the rotors being marked up by the pads yet so not sure the pads are being applied with enough pressure. Not really sure what bedding is as I have never done a new brake system on a car before. I will look into it and test the booster for leaks overnight
I notice my booster is not holding vacuum. I pumped it to 15 inches of Hg vacuum and it immediately starts bleed down some. It will slow at around 10 inches but definately does not hold overnight. Few hrs and its out.
So I guess I need a booster and possible bedding procedure. Any recommendations for a booster/master combo? Would a c4 vette or 4th gen setup work?
Good thread, same boat as yall, everything has been changed but the prop valve and my brakes still work for crap. Though I can engine brake with the stick so I am able to still stop ok-ish.
checked the booster hose and nada
Only thing I got left to change is the prop valve, but sounds like thats not a 100% fix for this.
Feel like I got manual brakes but the booster is fine..........
__________________ 86 Pontiac Firebird [68 Firebird HoodScoops, Notchback, Rear Mounted Tach, Inverted Wing,
T/A HoodVents in SailPanel, Front & Rear STB, Boxed LCA/PanHard, Fulley Welded Interior, Alston SFC] http://www.thirdgen.org/techboard/v6...-all-over.html
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14psi, pump gas street tune 
