i have a question? i changed my brake pads on my 89 c4 and now it doesnt want to stop. i first put on cheep pads and it was scarey. i put on raybestos pads and it got better. it feels normal under normal stopping but when you need to stop quick it takes both feet and a boat anchor . you cant even lock it up in rain. help

 

i have a question? i changed my brake pads on my 89 c4 and now it doesnt want to stop. i first put on cheep pads and it was scarey. i put on raybestos pads and it got better. it feels normal under normal stopping but when you need to stop quick it takes both feet and a boat anchor . you cant even lock it up in rain. help[/QUOTE]

 

It sounds like you do not have any power assist from the power brake booster. See if you have vacuum to the booster, see if you have low vacuum caused by a leak in the brake booster diaphram.

 

silly question.... but did you cut the rotors. did you get anything on them.

Youd be suprised how little it takes to contaminate a apd/rotor

 

yeah, douche em with some brake cleaner and get all the greasy fingerprints off.

 

yes i cut the roatters and polished them to a 220 grit. they were clean. this has been like this for a couple of months. also checked vacuum and replaced power booster with new one . replaced master cylinder.

 

ABS won't let you lock em up in the rain! You must have frozen calipers.

 

Polished the rotors with 220 grit? I musta missed that trick in the Helms book.... The brake pads need to grip the rotor. By polishing the rotors your pads can't grab.

SO! Take that sumabitch out on the open road and bed-in those pads. Run'er up to about 60 and stand on the pedal hard until it almost stops then, do it again. It might take three times until you break off the polish on the rotors. Its gonna smell like the bottom of the Grapevine Grade.... So keep driving about 10 minutes and let her cool off. Then try braking hard again and see if your brakes are starting to grab again.

Sound rough? You bet it is! Or take the rotors off and have em turned again and this time have your buddy smack you up-side the head if you even think about doing anthing to those rotors other than cleaning then with brake cleaner.

 

 

One other thought. The ABS system may be at fault. I met another 89 owner this weekend who's complaining of the same problem. Except his brakes "fail" on an irregular basis. He's replaced all the mechanical parts except the ABS Pump and computer.

 

Also, per JrRifeCooch's advice.... when doing the bedding, do NOT come to a complete stop. Just slow down then release, letting the car roll. Clamping the brakes down to a full stop with toasty hot rotors can easily crack them. Same applies to locking them up, but you dont have to worry about that with abs

 

hey jr, that was me this weekend.a gm tech told me to cut them smooth. 220 grit. it was a gm buleitin. smoother surface means more surface contact. its got to be something with the abs?????????

 

The abs senses when one or more wheels are not rotating and turns on a pump that modulates the brake line pressure from wheel locked to unlocked rapidly, it cannot reduce the line pressure while you are applying line pressure through the master cylinder. ABS is not involved. You have low friction or low caliper force. Air, pinched brake line, frozen calipers, or a flexible line having an aneurism are where I would be looking.

 

With the FoMoCo paint chip?

My daughters 99 Alero (ex) had an ABS computer failure as a result of a battery/alt problem. When she would brake for a stop, the brakes would just let go! (No modulation, just no brakes) She had all the pedal and no brakes. The Olds dealer replaced the module and with in a few weeks the problem returned. She traded the car in at the dealer. (Last thing I needed was a late night phone call from the CHP.)

This problem sounds simular.

ABS pumps are reasonably cheap on ebay. Might want to give it a try.

 

Gentlemen
To be fair to the ABS systems out there, let's set the record straight on the components and their respective functions. Your ABS system has:

Wheelspeed Sensors - ,telling the system how fast each wheel is rotating. Since you have 4 of these, basic mathematics can be used to figure out that your wheels are turning slower than they should be and the system needs to intervene.

Isolation Valves - ,these are located between your master cylinder and the brake cylinder. They are normally open, closing when you are applying too much pressure to a wheel with your foot. Hence, they "isolate" you from applying any more brakes.

Dump Valves - ,these are normally closed. When the Isolation valve is closed and your wheel still has too much pressure, the dump valve opens to release it.

Pump - ,The pump takes all that fluid that the dump valves just released and pumps it back into the master cylinder.

NONE OF THESE THINGS MATTER IF YOU CAN'T LOCK A WHEEL. Now you could potentially have a system fail (although they are designed NOT to fail this way) such that it totally isolates you from braking and you feel like a hockey puck. However, they can't "partially" isolate you from the brakes as you describe. Something in the basic brake system is affecting your braking (i.e., clamping force or friction force).

My 2cents.

 

i am takeing in all of this stuff. im just scratching my head....................

 

im beginning to think i have a miss match between pads and roators.maybe someone before me put aftermarket roators on it?

 

This guy got a bit over zealous bedding in his brakes.

 

Damn I want some of them pads!

 

WOW!! thats some serious chit there...