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Discussion Starter #1
I have noticed a strange knocking sound when I press the brake pedal all at once ( hard braking) that is felt at my foot.However , when I press the pedal gradually nothing is heard or felt. I have the brake examined visually by a mechanic , everything seem normal. Any suggestion is appreciated.
 

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Mechanic may think it's normal but he may have not really looked at it (often happens, mechanics are busy).

I think it could be your rotors, bumpy, wobbly, or abnormal feeling braking can most often be due to warped rotors.

How many miles are on your odometer? How long have you had the car?
 

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Discussion Starter #3
My odo about 150,000 km.
Somebody told me it may be the sound of ABS kicking in every time I press the brake hard because I have almost worn out tires.
What do you think of this possibility ?
 

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Well at 150,000km (94,000 miles) brake rotors are a definite possibility. The ABS possibility sounds unlikely. Worn tires aren't good, but ABS shouldn't be activated by them.

When was the last time you had new rotors and brakes?

I imagine a nice new $200 set of NAPA rotors would fix your problem. You can put them on yourself. I recommend a gear puller from harbor freight ($8) to get the old ones off as they can often be stuck on.

DON'T ever buy cheap rotors like from rockauto or random places. They are chinese and warp. That warpage causes the problem you are describing. Unsmooth braking, bump or knock feelings on brake pedal, vibration of brake pedal, etc.

If the answer to when the brakes were last changed is "you don't know", I'd spring for new rotors and bet that totally wolves the problem.

Old rotors (and cheap Chinese rotors) warp and cause braking bumps, vibration, etc on the brake pedal.

It just happens, it's common. Extremely common on a car at 93,000 miles like yours. Probably past overdue, (I just changed brakes on a 80,000 mile car and they were down to almost nothing!) So that's why you are hearing noise I would bet.

Sure, the mechanic can check the pads and make sure they're fine, but he can't check if a rotor is warped unless he drives the car for a diagnostic test drive, or takes the rotor out and see if it is truly flat.

That's why you have to replace them and see. That will solve your problem I would bet.
 

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Somebody told me it may be the sound of ABS kicking in every time I press the brake hard because I have almost worn out tires.
What do you think of this possibility ?
Unlikely unless it's raining or something. If your rotors were warped, you would feel a pulsating brake pedal when braking.

When's the last time the brakes were serviced/cleaned/replaced? I'm thinking a dirty/rusty caliper (more precisely its guide pins). If it's been a while, it wouldn't be a bad idea to get a servicing, it's not very expensive.

My GF had a similar issue with her Tiburon. She just ignored it for a long time, and when I finally got to bring it to the garage to get the caliper replaced, I passed by the garage by accident, hard-braked and the caliper pretty much exploded. :D
 

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Discussion Starter #6
Well at 150,000km (94,000 miles) brake rotors are a definite possibility. The ABS possibility sounds unlikely. Worn tires aren't good, but ABS shouldn't be activated by them.

When was the last time you had new rotors and brakes?

I imagine a nice new $200 set of NAPA rotors would fix your problem. You can put them on yourself. I recommend a gear puller from harbor freight ($8) to get the old ones off as they can often be stuck on.

DON'T ever buy cheap rotors like from rockauto or random places. They are chinese and warp. That warpage causes the problem you are describing. Unsmooth braking, bump or knock feelings on brake pedal, vibration of brake pedal, etc.

If the answer to when the brakes were last changed is "you don't know", I'd spring for new rotors and bet that totally wolves the problem.

Old rotors (and cheap Chinese rotors) warp and cause braking bumps, vibration, etc on the brake pedal.

It just happens, it's common. Extremely common on a car at 93,000 miles like yours. Probably past overdue, (I just changed brakes on a 80,000 mile car and they were down to almost nothing!) So that's why you are hearing noise I would bet.

Sure, the mechanic can check the pads and make sure they're fine, but he can't check if a rotor is warped unless he drives the car for a diagnostic test drive, or takes the rotor out and see if it is truly flat.

That's why you have to replace them and see. That will solve your problem I would bet.
I have recently changed the pads.But I have'nt changed rotors since I bought it ( more than three years)so your diagnosis is valid.Thank you.
 
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