**READ ME** ABS wheel Speed sensor.....WARNING!

[ALPINE]

Under advice taken on here that i could drive the car with an intermittent jibby Wheel speed sensor i will warn you all...


DO NOT DO IT!

just tryed to stop with my 7 year old in the car comming up to a major busy round about to put my foot on the pedal for it to just spaz out and not slow me down! i had to no only stop us from hitting the car that was stopped at the round about, but slide sideways between the car stopped and the van the stopped the other side of it...AND not hit anything or slide into the 350Z flying round the round about! Glad my hand brake works!

to top it off it seems we left the haribos on the self service counter without putting them into the bag!

Rant over...

 

[leshkin]

Bummer man! Glad you are all OK.

 

[Dani_B19]

**** me mate, glad you and the kid are ok.

Bummer about the haribos

 

[martin g]

glad your all safe

 

[Broken Byzan]

ABS fails safe, it must have been greasy too to make it do that.

However, glad you had your wits about you, i wouldn't want any harm to come to you or your little family

 

[s3dave]

scary....glad your both safe :icon_thumright:

 

[ALPINE]

thanks peeps.

im buying 2 sensors tomorrow.. i like my wife and kids and fancy keeping them for a little longer. plus.. i cant sell a car with moody brakes.

 

[beachbuggy]

Agree with ByzanA4 it should fail safe. Sorry to here what happened though, hope your all ok.

May be worth getting the ABS pump checked with VAGcom as it could be that.

 

[ALPINE]

what you mean by fail safe... there was nothing safe about it!!! the ABS went mantal as the roads a little bumpy, other than the abs buzzing the pedal, it was as if the brakes did not work. I have vag com`ed it and it says left front wheel sensor intermitant.

if its the pump im braking the car simples.

 

[Prawn]

as people have said above, abs fails safe.

However, what can happen, when a sensor is going dodgy, is that the ABS can THINK it's working, most often when it's getting intermittent signals from a wheel, so it'll THINK it's working just fine and that one wheel is locking up (sensor loosing signal).

The error you made Alpine, is driving the car when it's in that indecisive stage of not knowing if it's broken or not. That can cause the ABS to trigger randomly.

if it's completely broken, the light will stay on and it'll be 100% OK, just without ABS.

If the lights out but you're getting it comming on and off sometimes, pull the fuse to be safe.

 

[s3dave]

all abs systems should be fail safe thats why you can pass the mot with the abs light on....but like all mechanical things , they can and do go wrong like fail safe thermostats....

 

[ALPINE]

the lights been on for a couple weeks prawn. had no problems what so ever. took me by suprize i tell you this.

i dont get all this fail safe shizzle.. by brakes did not work. how is that safe?

 

[s3dave]

the lights been on for a couple weeks prawn. had no problems what so ever. took me by suprize i tell you this.

i dont get all this fail safe shizzle.. by brakes did not work. how is that safe?

as i understand it, if there is a problem all solonoids/valves in the abs should remain open in the event of a failure, so it reverts back to a car without it...

 

[ALPINE]

thanks dave. so moneys on the ABS pump then. as i have said, the pedal went mad with the abs doing its thing, but the car did not even slow. surely vag-com would show a error code if the pump was at fault. Fail safe or not.. i had no brakes. (tho was fine the slow 2 mile drive home)

 

[ALPINE]

mite considder braking the car if i cant find out whats wrong tomorrow. so any one whating bits Pm me what you want and ill see if its worth my while. maybe make an offer on the whole car. i cant be ***** to fight with it as im getting a new car soon. i only want a little extra money to get extras on the LCR.

 

[jojo]

The vultures are circling.

 

[mike_plymouth]

PM sent

 

[1.8tplym]

I had something very similar with a 99 passat i owned previous to the Audi. Took it into the garage for cv joint to be replaced and on driving it home the ABS kicked in under very light breaking. intermitant initially so i took it back to the garage who denied all responsiblility and said that the car was fine! Driving it the next day and started to brake and the ABS kicked in far toearly and i only just managed to stop the car. After a very heated phone call with the garage they came and collected it from me and came to the conclusion that they 'may have' broken the wheel speed sensor when in for the cv so out of good will they would replace for free?! Suffice to say i 'politely' told them my feelings on the whole matter and havent used them since. Scared the crap out of me!

 

[ALPINE]

i think it is the wheel speed sensor tbh.. vag-com dont lie and it makes sense. dont particually wanna brake it as its just a mission.

mite well get new sensors and sell the motor cheap tho if im honest.


Mike plymouth... as regards to your pm ill keep you posted and yes you have 1st dibbs

 

[beachbuggy]

Just to clarify. The ABS computer constantly monitors the signal from each wheel speed sensor. When it senses that any of the wheels are approaching lock up during braking, the ABS computer sends the signal to the hydraulic control unit, which modulates the braking pressure for a corresponding wheel(s) preventing it from locking up.

It does this by opening a valve in the control unit, releasing pressure in the caliper then reapplying the pressure.

If the control unit detects a fault in the system, either in the computer, sensor or pump then it will display the warning light on the dash. When this happens the control computer disables the control unit thus making the ABS redundant. You are left with normal brakes in that when the wheels lock they should stay locked.

This is called "fail safe".

However this is a little misleading! A car with ABS is by nature is much safer than a car without ABS, and hence why used.

The term "fail safe" refers to the fact that should the system fail, then it will fall to a state which can safely be runwithout the use of automatics to control the braking. It doesn't refer to the effeciency of the braking it's self just to the action required, IE the need to stop the car.

Pulling the fuse for the ABS will disable the ABS and you should be left with a stock hydraulic braking system.

Have you by any chance replaced the brake fluid recently or let the fluid run low at any time? If you have then you can get air in the ABS pump and unless you do the ABS pump cycle in VAGCOM you wont clear this and it may only show when you lock the brakes.

 

[1.8tplym]

If the control unit detects a fault in the system, either in the computer, sensor or pump then it will display the warning light on the dash. When this happens the control computer disables the control unit thus making the ABS redundant. You are left with normal brakes in that when the wheels lock they should stay locked.

That certainly was not the case with my Passat. No Light at all on the dash. Just intermittantly would kick in the abs under any type of braking. it was only the one instance when the abs seriously affected my stopping distance (and yes, it was dry) but it was enough to scare the carp out of me! The garage admitted that they had damaged the wheel speed sensor (eventually) and once replaced no more abs problem! Im certainly no mechanic but i know when the abs kicks in and i certainly knew that the car didnt want to stop lol!

 

[beachbuggy]

That certainly was not the case with my Passat. No Light at all on the dash. Just intermittantly would kick in the abs under any type of braking. it was only the one instance when the abs seriously affected my stopping distance (and yes, it was dry) but it was enough to scare the carp out of me! The garage admitted that they had damaged the wheel speed sensor (eventually) and once replaced no more abs problem! Im certainly no mechanic but i know when the abs kicks in and i certainly knew that the car didnt want to stop lol!

Ok, but then if you had no light on the dash then the computer hadn't detected a fault in the system and thus not gone into a fail safe mode!

You are right though, if the garage had damaged the sensor or misaligned it, then you are likely to get dodgy braking as the computer is probably recieving duff information and acting accordingly.

My point is that should the ABS computer detect a fault, not due to bad mechanics! then it will give you a warning and then go into a fail safe mode. If you have no warning, as you did, but there is a problem then you will possibly, as you found, have seriously affected braking.

 

[ALPINE]

..