Blue88

My 88 will not do a panic stop and it takes both feet and a prayer to get the thing to come to a quick stop. The rear pads wore out so I replace the pads all the way around. Replaced the master cylinder and bled the lines. A few months later I am having to replace the rear pads again. Front pads aren't even half worn but they are wearing some due to the brake dust on the wheel. The pedal is really firm but feels normal until I get in the wifes old Chrysler and touch the brakes and it nearly puts me through the windshield just stopping for a stop sign. Is my booster bad or could it be a check valve? Hate to spend alot of money on a booster when a $5 valve will fix the problem. I don't hear or see any vacuum leaks. Thanks in advance for any input you have.

bogus

check the check valve first, cause it's cheaper.

But one is bad.

As for rear brakes wearing so fast? Sounds like you have a hung up caliper.

Blue88

I don't think it is a caliper hanging because the pads on both brakes were worn equally. It appears that most of my stopping power is being delivered to the rear brakes instead of the front. Someone told me to check the proportioning valve. There is supposed to be a small pin on it that controls the amount of braking force between the front and rear and to center the pin if it is pushed all the way in. I have yet to find the little pin and it is supposed to be located somewhere near the emergency brake light switch. I have driven cars in the past that had bad boosters in them and you definately know when you have no power brakes. My car feels like it has good brakes until I have to brake suddenly and that is where things get real exciting. Thanks for your response bogus. I will get a new check valve from the dealership tomorrow.

gpagaduan

I don't know what a check valve is or where it's located. Can you please enlighten me on what this part does? Also, is this part normally replaced after years and years? It's about the only thing I haven't replaced in my 90...maybe because I've never heard of one.

bogus

sorta normal.

It's on the brake booster, where the hose plugs in.

gpagaduan

Would that be replaced as part of a normal brake booster replacement job? I had the booster done about 4 years ago. I'm sure I'll never find the work order to see what parts were involved in addition to the brake booster. Thanks for the info.

bogus

I would think that, yes, this is part of the booster.

dndrsn

hey blue 88, i got the same problem on my '94. i had the pads changed, new booster, complete bleed, and its the same thing. normal driving it seems fine although a little firm, but in a panic stop i feel like fred flintstone dragging my feet out the door. I have an '02 monte carlo ss with all discs and it will throw you out the windshield with minimal pressure on the pedal. i know there are 8 years difference between the cars but it shouldn't be that different. if you find out how to fix it please let me know.

94redrag

Hey, have you two (blue88/dndrsn) been driving my car? You just described the way my car stops. I haven't figured it out yet either!

Zane

SLOWRIDE

65Z01

Well the only extreme breaking I've done with the Vette has been at the big end of the 1/4 mile while bracket racing but they would really grab when called uppon to do so.

I didn't know there was a check valve in the MC; I've just had the lines off mine and cannot see such an animal in there. Since it looks like I'm in for a rebuild of the MC, I'll check when in there if I go the kit route.

It's possible that the front brakes are not engaging well enough and so the rears are wearing out quickly. This would also account for the lack of stopping ability too. I tend to think this kind of problem is in the MC. Remember that the MC for an '88 is unique to that year; maybe someone use one from another year and it's not performing well.

If there is a pin that controls proportioning it must be within the MC as there is only one rod from the booster into the MC.

mitchcole

Here's a chime in from another guy with the same problem. My master is on the way out (I can pump up the pedal).

Bought a new one and a replacement brake bias spring. I'm going to put it all in this Sunday.

As far as front to rear - I'm not going throug pads on either end quickly.

It seems like the pads on the car are racing pads that need to be heated up before they really start to work well. When you take the car through the mountains and get on it - the brakes work great when hot. But cold panic stopping is terrible. Do you have the same situation with brake temperature?

corvette-pilot

Sounds to me like it is working normal??
When I first got my 94 I thought the same thing.
Even now is city driving I don't think it stops as good as you would think.
So I'm looking into the C5 upgrade right now and am gathering the parts.
I figure a larger rotor and dual piston caliper instead of a single should help.

Someone had told me it was designed this way. The brakes work great at bringing you down in speed when going fast. If the booster had more power to make it stop faster in city driving I thing you would kill yourself at high speed if they grabbed too good. guess it is a compromise.

JMO

Da Mail Man

Greetings All,

Mine (1988) Seems To Be As All You Have Described. It Seems That I Am Braking On Either The Front Or The Back And My Guess Is That It Is The Back.

I Don't Have A Lot Of Stopping Power In Any Regard And System Is Tight And So Are Pads.

I Forgot All About Replacing Check Valve In Vacuum Brake Booster So, Will Do Tomorrow.

I Have Noticed That The Front Brake Reservoir Has " Used" A Little Brake Fluid Over The Past Few Months And I Assure You That There Are No Leaks. I Assume That It Is Due To Front Pad Wear However, The Car Does Not Brake Like They Are Even There.

Blue88

I replaced the master cylinder thinking that this would fix my problem. I have done brake jobs on older cars where the proportioning valve had gone bad and this would cause zero or little braking on the front pads. I'm not real sharp on the ABS stuff so I have not been able to trouble shoot the thing. I put some $70 pads on the front when I bought the car and thought that might fix the problem. I put some cheaper pads on and still the same problem. I am going to the parts store tonight on my way home from work and will see if they have one in stock and swap it out. I'm sure that Autozone should have it since this is a pretty common part on GM. Running a leakdown on the booster will help as well. I also have noticed that the front reservoir has to be topped off way more often than the rear. Might just be something that I will have to put up with since so many have reported the same problem. Seems to me the brakes should toss me through the windshield like the wife's old 5th Avenue that has a stock disks on the front and drums on the back. If I find a fix I will post it.

dndrsn

Hey Blue88 I'll be watching. In the meantime I am thinking of taking my '94 to Jupiter to the Corvette Center and have them test drive it. They only work on Corvettes and if there is a problem on these cars I am sure they would know. I just put thin spoke wheels on my car and would like to upgrade the front brakes to C5 if for no other reason than for looks, but before I do the upgrade I would still like to know if the stocks brakes could be improved.

mitchcole

So, I installed a new master cylinder modified with the different rear bias spring.

After bleeding all the brown liquid out of the lines - this car now stops on a dime. Same old pads/rotors/calipers. 12" front brakes. What a difference. When I hit the brakes hard from a good clip, the rears tires make noise and the ABS turns on quicker - but the results are outstanding.

my braking problems are finally solved.

dndrsn

How much did the Master Cylinder set you back ?

Blue88

Excellent news mitchcole. Where did you purchase the spring? I have seen one advertised in the Mid America catalog for $20 and had thought about trying it. If this worked for you then I will order one tonight if it can't be purchased locally. Thanks for posting!

mitchcole

The master cylinder was bought on EBAY ( http://cgi.ebay.com/ebaymotors/ws/eB...category=33566 ) for $89. It's the exact same item as factory - I duno how this guy got them so cheap...