Brakes going out

[SHOguy 92]

About 2 weeks ago the same day my front driver side wheel bearing went bad I noticed a funny feel to my brakes.

Since then it has progressed (although it seems like it stopped getting worse). When I push the brakes now they go to the floor, they do work, just lightly, then if I let up I can pump the pedal to get some pressure back in the pedal and they work ok. But will soon drop back to the floor if I don't keep pumping.

I got an ABS light on for about 5 seconds a week ago. The ABS still works and If it comes on the brakes work like normal because the ABS pulsing pushes the pedal back up giving me more to work with.

Anyone got any ideas?

 

[ultimatesho]

my 92 is doing the exact same thing..........

my front bleeder ******* r stripped out tho so im hopin its just air in my lines........plan to eather do a 96 upgrade or a cobra upgrade really soon anyways

 

[93rev2sev]

Either air in the lines or an internal seal is gone. Does the car pull to the left or right when you hit the brakes the first time(without pumping the pedal)? When you pump the pedal, does it still pull?

If it stops straight but just has a really soft pedal, then it's probably not a caliper. I would suspect the Master Cylinder first.

the other thought is that the ABS sensor rings are dirty or greasy and sending false information to the computer.

Start by inspecting the ABS rings...look for grease from a blown out CV boot...that will screw up the ABS system for sure...and might cause the pedal to go to the floor(usually you will hear and feel the ABS pump trying to activate).

Good luck, keep us posted.

 

[itwonder]

Check all lines and calipers for visible fluid leaks. If none found, suspect Master Cylinder. Assumes you have not opened up the brake system in the recent past for some reason.

 

[Storm-Chaser]

Have you bleed the brakes since replacing the wheel bearing? Bad wheel bearings can cause the problem you're describing.


I've seen ABS tone rings packed with grease that worked fine. The ABS sensor is a hall-effect sensor that generates an electrical wave-pulse as the metal vanes pass the magnet in the sensor. Where I have seen it create a problem, is when the CV joint begins to deteriorate due to the lack of grease and then coats the grease and tone ring with metal particles. A bad wheel bearing, if allowed to progress for a period of time could do the same thing - coat the tone ring build-up with metal dust/shavings.

A bad wheel bearing can generate considerable heat. I've seen rotors and rims coated with wheel bearing grease that became semi-fluid from the excess heat, and thrown-out from the hub.

Both high rotor temps and metal shavings can damage the piston seal, allowing air intrusion into the system or resulting in fluid leaking, which are other potential sources the OP's symptoms suggest (pedal fade, responds to pumping). If the ABS were malfunctioning, it should result either in the ABS system failing to work, or to work incorrectly or at incorrect times - but in the latter cases result in the charateristic ABS pedal-pumping.

• check for leaks
  
  
• inspect the piston seals
  
  
• bleed the brakes

The master cylinder may also be a problem, but I would address the easy/inexpensive solutions first.

Either air in the lines or an internal seal is gone. Does the car pull to the left or right when you hit the brakes the first time(without pumping the pedal)? When you pump the pedal, does it still pull?

If it stops straight but just has a really soft pedal, then it's probably not a caliper. I would suspect the Master Cylinder first.

the other thought is that the ABS sensor rings are dirty or greasy and sending false information to the computer.

Start by inspecting the ABS rings...look for grease from a blown out CV boot...that will screw up the ABS system for sure...and might cause the pedal to go to the floor(usually you will hear and feel the ABS pump trying to activate).

Good luck, keep us posted.

 

[shotime9]

This same thing happend to my 94 sho. I ended up having to replace all four calipers and it solved the problem.

 

[SHOguy 92]

I been down and out with the flu for a few days, anyways now I'm back.

The car doesn't pull either direction when I put down the brakes right away also doesn't pull if I pump them.

Also when I did replace my wheel bearing I just unplugged the ABS sensor under the hood and brought in the knuckle to the machine shop like that, I didn't feel like having to force that sensor out and put another in.

Also there is no fluid loss that I can tell off, I haven't got a chance to get it into a shop and I don't feel like crawling around in -20 weather outside right now, but I have been monitoring the brake fluid and it's been full for the 2 weeks this has been happening.

 

[Storm-Chaser]

Do a search for the term "disc brake kick back" (it might be knock back), and it will describe how bad wheel bearings can cause the type of brake problem you're describing.

 

[93rev2sev]

I would also make sure there is no movement in the wheel from either a bad wheel bearing or a loose hub nut. Jack that corner and try to wiggle the wheel.

If you just had wheel bearings done, you should probably check this anyway...cause if they are going to fail...they are going to fail quickly.