General Noise and scraping while braking

[Mustapha01]

Hello everybody,
i've got a Punto 2001 1.2 8V with ABS system. I feel and hear noise and scraping while braking. I also hear the abs motor turning very fast. what's more weird is when I unplag the wires from the brake pedal sensor the noise and the scraping go away and the brake system works great. I'm pretty sure there is a link between the brakes sensor, which is related to the stop light, and the abs module. BUT i can figure out how the sensor affects negatively the abs module.

sorry for my english
any idea will be appreciated.

 

[Ziggy122]

If ur hearing the abs pump activate under braking and its happening even tho the wheels shouldnt be locking up (skidding)


Then unplugging the sensors means it dont know that the wheel is false reading its status and doesnt react

You probably have a dead sensor or a broken tone ring / reluctor ring somewhere

 

[Mustapha01]

i've just changed the rear wheel bearings hubs + abs module; but i have no idea about the condition of the front bearings. i did a test for all four sensors and they seem okay.

 

[Joao Gomes]

i've just changed the rear wheel bearings hubs + abs module; but i have no idea about the condition of the front bearings. i did a test for all four sensors and they seem okay.

As long as there is no humming noise when driving at speed they're probably okay

 

[Mustapha01]

I think of cleaning the sensors and bearings, i hav no idea how to proceed

 

[judderbar]

Hello everybody,
i've got a Punto 2001 1.2 8V with ABS system. I feel and hear noise and scraping while braking. I also hear the abs motor turning very fast. what's more weird is when I unplag the wires from the brake pedal sensor the noise and the scraping go away and the brake system works great. I'm pretty sure there is a link between the brakes sensor, which is related to the stop light, and the abs module. BUT i can figure out how the sensor affects negatively the abs module.

sorry for my english
any idea will be appreciated.

What actually do you mean by noise and scraping when you use the brakes with the brake pedal sensor attached?

Are you talking about a metal on metal type of horrible sound or are you describing the way the ABS unit changes the feel of the pedal?

I think you will make more progress if you can work out where that noise is coming from.

So can you explain more about the kind of sound you are hearing?

 

[Mustapha01]

What actually do you mean by noise and scraping when you use the brakes with the brake pedal sensor attached?

Are you talking about a metal on metal type of horrible sound or are you describing the way the ABS unit changes the feel of the pedal?

I think you will make more progress if you can work out where that noise is coming from.

So can you explain more about the kind of sound you are hearing?

It's the way the Abs changes the feel while I push the brakes pedal. It feels like the pedal is hesitating and vibrating and i can hear abs motour turns even when I move my foot off the pedal. This happens only while braking on low speed when you don't need to push harder unlike while driving with higher speeds (above 60km/h)

 

[judderbar]

It's the way the Abs changes the feel while I push the brakes pedal. It feels like the pedal is hesitating and vibrating and i can hear abs motour turns even when I move my foot off the pedal. This happens only while braking on low speed when you don't need to push harder unlike while driving with higher speeds (above 60km/h)

1. I suppose it makes sense the ABS unit is only activated when the brake pedal sensor detects you braking and so without the pedal sensor connected you get no ABS activity.


2. The following thread might be covering your problem? The problem could be caused by unbalanced braking of the wheels which the ABS system is correctly detecting and trying to correct.

https://www.fiatforum.com/punto-ii/287350-my-punto-mk2-brake-problems.html

That thread also shows the front ABS ring is part of the wheel bearing and what you need to do to get access to it.

 

[Mustapha01]

The front wheels size = R14, 165, 70
The rear wheels size = R14, 175, 70

Can the different size be the source of the problem?

 

[Brendan W]

The back are bigger diameter so will be turning more slowly than the front.
The ABS might not like that and could be interpreting it as either back end lockup or front end spin.
How long have the tyres been like this?

 

[Mustapha01]

about a month ago, since i bought the car. i'll try to change the rear tyres and post the result.

 

[Brendan W]

about a month ago, since i bought the car. i'll try to change the rear tyres and post the result.

Most ABS systems seem to have a tolerance of 8-10% difference in tyre diameter. This is more than the difference between the 165 and 175. ~5%
If the front are more worn than the back this could make the actual difference greater as could a difference in pressure.
Before changing the tyres I would try reducing the pressure in the back for a test.

 

[Mustapha01]

Most ABS systems seem to have a tolerance of 8-10% difference in tyre diameter. This is more than the difference between the 165 and 175. ~5%
If the front are more worn than the back this could make the actual difference greater as could a difference in pressure.
Before changing the tyres I would try reducing the pressure in the back for a test.

Actually the front tyres are worn than the back tyres. I'll try to reduce the pressure and post the result.
I'm also thinking of fitting 4 (R14 60 185) tyres. Can this affect the abs system? because i believe this tires' size is not stock specs for the car.