Intermittent Grinding Noise on Braking

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  #1  
Old 07-05-11, 03:16 PM
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Intermittent Grinding Noise on Braking

99 Chevy Malibu V6 Auto 122K.

Wife's car makes a grinding sound from the front end intermittently when brakes are applied. The brake pedal feels fine and the car stops as normal whether the sound occurs or not. Sound is not metallic or high pitched Front brake pads are about a year or so old. Rear brakes are drums and have not been checked, although sound comes from front of vehicle.

I'm trying to assess what to look for before I dig in to taking the car apart.

Thank in advance for ideas/suggestions.
 
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  #2  
Old 07-05-11, 03:26 PM
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Regardless of when the pads were last changed I would check them all again for wear. Sticking calipers can cause problems for one thing. Also might want to pull off the rear drums and have a look also at the same time. Once everything is confirmed OK, then other possible causes around bearings and drive shaft could be next to think about.
 
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Old 07-05-11, 07:58 PM
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allen, it's BRAKES. your wife's LIFE is at stake there. it is no big deal to take them front brakes apart and inspect.
 
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Old 07-05-11, 08:44 PM
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Will do in the AM. I'll report what I find.
 
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Old 07-06-11, 04:35 PM
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OK...it does look like the caliper is sticking. The rotor is RAGING HOT and I'm having trouble pulling it off as it seems to be pushing the pads onto the rotor.

1) How can I remove the caliper based on its current status?
2) Once I get it off, is there a way to UN-stick it? Must the caliper be replaced?

Car is in pieces, wife needs to go to work in the morning.

Thanks, as always.

az
 
  #6  
Old 07-06-11, 05:02 PM
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well, you let it cool, first.
you did not grease caliper guides, did you, when you did the job last time?
you need to cool it down. hopefully, it'll loosen up some so that you can remove caliper side pad. if not, spray some quick wrench around piston edge and pry it in with a prybar between rotor and brake pad. at this point, few scratches here and there are irrelevant. thereafter, the usual - large C-clamp and press it in.
calipers are completely re-furbishable, and not hard to do this. hardest is to press piston out, if uou do not have compressor. you have to use brake pedal - carefully, or remove it completely and use vise to pull it out.
general cleaning of piston and bore, and O-ring replacement. you will end up with air in the system and will have to bleed it all.
problem is not this. problem is to determine exactly why it was dragging. not nerecessily caliper. can be line obstruction or something in regulator or even in master.

glad you caught it on time though.

hey, but wouldn't rotor float free the very moment you remove wheel and front pad? and then you have full access to caliper?
 
  #7  
Old 07-06-11, 05:04 PM
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Without seeing the situation it is difficult to provide detail advice around the condition of things, but assuming that the pistons are moving freely, once you unbolt the caliper form the spindle and slide it off the rotor you will need to clean it with brake cleaner and then apply brake/caliper grease to the slider to free it up. What is the condition of the rotor and the pads?
 
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Old 07-06-11, 05:23 PM
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Piston is stuck in "out" position, pressing on the pads. Pads are pressing on the rotor, so the whole thing is stuck. I cannot get to the pads because of the pressure the caliper is placing on them. If I can get one pad off, I'm sure I can get the caliper off.

It looks like the pads have significant wear. I will replace the caliper and pads. The rotor appears to be in good shape.

Only problem is how to get the caliper off the rotor.

Will try the liquid wrench to see if I can loosen it.

...and no, I didn't grease the caliper guides. (Never heard that instruction...now I know.)

I'll keep you posted. No pun intended.
 
  #9  
Old 07-06-11, 06:13 PM
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Got the caliper off with a Big Effin' Hammer.

Pads are worn down to nubs. Stopping tonite. Will resume in the morning.

Any other potential hazards to look out for? Stuck caliper looks like the culprit. Could something else have caused the problem? Besides not greasing the guides, would anything else cause the caliper to stick?
 
  #10  
Old 07-07-11, 07:01 AM
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Sometimes the flexible brake hose connecting to the caliper from the brake line can collapse inside and hold fluid pressure in the caliper rather than releasing it back to the master cylinder. This could be your problem also. If not, and the piston is not stuck you should be able to manually push it back into place by applying pressure to the rotor side of the pad. If you open the bleeder and this releases a squirt of fluid and loosens up the caliper piston you are probably looking at a brake hose problem. You could end up replacing the hose, the caliper, pads, and possibly the rotor depending on what the surface condition is, how much material is left on it to even be resurfaced.
 
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