SCARY ABS

[STORM 2 0]

Hi folks

just replaced the front offside ABS sensor (GSF replacement) and have a major problem. The warning light is now OFF, so it looks like the sensor did need replacing.

However the ABS seems to activate at any opportunity under braking. Occurs especially just before coming to a halt or even worse when gently braking at normal speeds - leading to some pant wetting moments.

Is there some sort of ABS reset procedure?

Also when it does cut in, the warning light fails to come on to let you know that the ABS system has been activated?

 

Any ideas?

cheers

[Supercharged 2]

Compare the resistance of that sensor with the other side - I assume the GSF one was not an ATE part - it may be that you have to change the other side to match...

[tandino 0]

Check to see if the front sensors are 'handed' parts, ie os and ns.

I had this problem on my old 325i i bought years ago, garage had replaced front ABS sensors and fitted them on opposite sides.

Once id fixedthe burnt out ABS wiring (ABS problem no.2) i drove the car down the road and nearly ended up in the back of the car in front.....

[grimmy 0]

I'm very intersted to hear the outcome of this too. Since lowering my car the abs has been very off and on. Excactly the same symptoms as stated by Storm2, if the light is out and the abs is "working" then when gently braking up to a junction you can feel the brake peddle push up against your foot and the car brakes very heavily with abs kicking in. But when you go over a bump the light comes on, the abs stops working but the car breaks normally. I dread starting the car and seeing the abs light out, and i aim for a cats eye to ensure a safe journey to work :oops:

[STORM 2 0]

OK, just had another look at the car.

Specifically, I suspect the problem is the gap between the rotor and the sensor. Replacing the VAG sensor with a GSF one may also have something to do with it. Went up to VAG today to see if I could get an original sensor to match my non faulty one, but guess what? They only do a replacement (siemens i recall) which I think is the same as the GSF one apart from the price (VAG PRICE £50---GSF PRICE £15

Anyway bought another sensor for the other side from GSF and made sure that both sensors were equally placed from the rotors about 5mm away. The gap wont be uniform as the wheel spins with 11 year old rotors but I don't think that was causing the problem.

 

I haven't tried the car yet, but I m hoping it wil solve the problem. If not I'll just disconnect the sensors and do without ABS - its much safer than having no confidence in your braking. :shock:

[STORM 2 0]

Grimmy, I suspect that while installing the suspension it may be that the sensor may have been knocked out of sync with the rotor. So you may have a situation where one gap is small and the otherside may be large - i think this confuses the ABS into thinking the wheels may be locking each time you press the brake pedal. Because you have an intermittent problem - I suspect that either the suspension unit may be knocking against the sensor, OR the sensor plug is under pressure. Once there is discontinuity the light comes on and you have normal braking (albeit withtout ABS).When there is connection the head of the sensor may be in a position that feeds erroneous input to the ABS brain, ie too far way or incorrectly aligned with the rotor. Bear in mind that it may be the rotor that has been damaged or warped during the suspension installation.

Worryingly, the ABS activated by itself today whilst taking a sharp corner, I didn't even touch the brake pedal

[dr_mat 0]

I had exactly this problem and it was a borderline sensor. Make sure your physical installation is good first, but you may well have another faulty wheel sensor.

[mattkh 0]

They only do a replacement (siemens i recall) which I think is the same as the GSF one apart from the price (VAG PRICE £50---GSF PRICE £15

Hi

can you put up a picture of the sensor please.

[STORM 2 0]

They only do a replacement (siemens i recall) which I think is the same as the GSF one apart from the price (VAG PRICE £50---GSF PRICE £15

Hi

can you put up a picture of the sensor please.

 

sorry mate - both GSF sensors are on the car mate. Unfortunately I still havent driven it because I fell asleep after the last post and just woke up now :shock:

[CorradoVR6-Turbo 0]

and are the ABS rotors running true and straight? ive seen many bent ones that dont run true due to long wheel bolts catching the rotor,are the gaps clean and evan?

[STORM 2 0]

Hurrah - problem solved! :D :D :D

[CorradoVR6-Turbo 0]

and it was...............

[dr_mat 0]

No, he wants us to guess.

[STORM 2 0]

sorry - all the details were in the earlier post - you lazy barstewards!

 

Basically - there are two issues here:

Firstly the system doesn't seem to like two sensors of differing makes. One was original and the other was a GSF part. So I fitted both with the GSF part.

Secondly, the gap between the sensor magnet and the rotor cage has to be minimal but not touching - it was a little difficult because like many, my rotors were a little warped but not too seriously. I managed to position the sensors with about say 3-8mm gap all way round.

 

Does that help?

cheers

[dr_mat 0]

Firstly the system doesn't seem to like two sensors of differing makes. One was original and the other was a GSF part. So I fitted both with the GSF part.

 

I think you had two faulty sensors.. but either way - fixed now..!

[mattkh 0]

Secondly, the gap between the sensor magnet and the rotor cage has to be minimal but not touching - it was a little difficult because like many, my rotors were a little warped but not too seriously. I managed to position the sensors with about say 3-8mm gap all way round.Does that help?cheers

Hi That was a great help.

Could brake dust bridge the gap if it was any less ?

[STORM 2 0]

Firstly the system doesn't seem to like two sensors of differing makes. One was original and the other was a GSF part. So I fitted both with the GSF part.

 

I think you had two faulty sensors.. but either way - fixed now..![/quote:pkjdtew9]

 

if that was the case, then the abs warning light would remained on after replacing one side. It went off however once the drivers side sensor was replaced.

[STORM 2 0]

Secondly, the gap between the sensor magnet and the rotor cage has to be minimal but not touching - it was a little difficult because like many, my rotors were a little warped but not too seriously. I managed to position the sensors with about say 3-8mm gap all way round.Does that help?cheers

Hi That was a great help.

Could brake dust bridge the gap if it was any less ?

 

Could do I suppose if the gap was less than 5mm - more likely flakes of corrosion from the hub arm / splash shield probably get in between the sensor and the rotor - remember the face of the sensor is a magnet so any ferrous crud gets drawn to it

[mattkh 0]

emember the face of the sensor is a magnet so any ferrous crud gets drawn to it

Hi

So that means no copper grease in that area. Cheers.

[STORM 2 0]

emember the face of the sensor is a magnet so any ferrous crud gets drawn to it

Hi

So that means no copper grease in that area. Cheers.

 

 

why? does the copper grease have a magnetic component, cos I though copper wasnt magnetic.....

[dr_mat 0]

I think you had two faulty sensors.. but either way - fixed now..!

 

if that was the case, then the abs warning light would remained on after replacing one side. It went off however once the drivers side sensor was replaced.

 

Faulty != dead!

 

Faulty sensors can read fine electrically, but produce bad results.