Brake Problems: They Start Coming On By Themselves!

[Tim Galaxy Fan]

Background

My car is an 03 Ghia 2.3 in the time I've had it I've had a couple of ABS rings and sensors replaced. When the ABS light came on about 2 months ago, the garage diagnostic indicated the Off Side front sensor had a "mechanical fault", this could mean that the ABS ring or the sensor was at fault. As the common cause of ABS issues is the ABS ring expanding due to rust building up behind it I decided to first renew the ABS ring. This did not cure the problem and the ABS light was still on. I looked on You Tube and found that sometimes for certain  fault codes a diagnostic tester is needed to reset the ABS light. As I had no issues with driving the car whist the ABS light was on, I took the car up to the Lake District, with confidence.

 

The Problem:

After about 10 miles of driving, I noticed the car starting to slow, as if the brakes were coming on. I stopped the car and sure enough I could smell break pad heat up particularly from the wheel where I had replaced the ABS ring. I decided not to risk the journey from Humberside to the Lakes and turned round to go home. However, the problem cleared and I decided, wrongly, to head up to the lakes. After another 100 miles ish the steering wheel began to wobble and the car slowed again. I pulled over and he same brake heat up and operation again had taken place without one touch on the brake pedal from yours truly. This happened more and more frequently, eventually I had to get the RAC  out as the wheels had locked and I was burning the clutch to make it move against the brake operation. The RAC guy did a diagnostic and determined that the sensor was out, he checked the ABS ring and said I had fitted it right. The RAC took the car home and I duly fitted a new ABS sensor, thinking that this would be the end of the problem. After a couple of test drives all seem to be OK. The ABS light was still on and needing resetting. However on a short shopping trip (10 miles) the same issue happened again: severe braking of the front wheel. The issue seems to be focused on the OS front as the disc is starting to look scored compared to the NS one

 

I spoke to a local Ford experienced mechanic and he said that he had known the securing clamps on the flexible portion of the brake pipes on the front wheels can become so puffed up with rust that they stop the flow of brake fluid away from the brake caliper, thus when the caliper gets hot the fluid expands and operates the brakes. I checked the flow rate of the brake fluid from the bleed valve and all seems OK, I took out the brake cylinder from the caliper and it came out easy as pie.

 

I'm at a loss and need help - is it possible for an ABS issue to create wheel braking of this type. Wife wants to ditch the car but it really is a great machine and I would like to fix it.

 

Thanks in advance

 

Tim

[daddyfixit]

it happens after driving a few miles?

try replacing the osf flexy hose itself, I have replaced hoses on a corsa van that had brakes sticking on....turned out to be the hoses breaking up inside and preventing fluid pressure from dropping---keeping the front brakes binding.

[BrianH]

I've had the same thing happen on an old Escort i had - again front ns flexi hose swapped and problem disappeared after that.

 

If you get it happen again opening the bleed valve should allow you to release the pressure, this will show that the caliper is ok.

 

Only other thing that might cause it is a failure of the abs unit, but this is not usually something that fails, I'd try the hose first before anything else.

[Tim Galaxy Fan]

Thanks for the advice, I'll replace the flexi as advised. I think the hose is OK as I passed brake fluid through it already and flow seems free but whilst the car's up on stilts it's better to be sure.

 

Another thought occurred to me: I read somewhere that brake fluid absorbs moisture and should be replaced regularly say every 1 to 2 years. I have bled the NS caliper (full replacement of caliper) and the two rear ones when I replaced the rear brake pipes, however never the OS caliper. The issue happens when the brakes get warm and the moisture in the brake fluid is released as vapour, this forces the cylinder on to the pad and operates the brakes. The heat generation increases and more vapour is released.

 

I'll replace the fluid throughout the system and cut into the old flexi and report back on what I find.

 

Thanks for the help. Regards, Tim

[sparky Paul]

Your ABS light should reset once you go over 15mph or so, if everything is working ok, so I would say you still have an ABS problem. I would have a guess at an incorrectly seated sensor. When you change the sensor, you must make sure that the scale on the hub carrier where the sensor seats is completely removed, or else the sensor will not reach close enough to the reluctor ring.

 

The brakes sticking on is probably coincidental, if the caliper piston and pads are all free, definitely suspect the flexible hose as suggested above. They break up internally, and the rubber can act as a non-return valve.

 

Brake fluid is hygroscopic, but I doubt that's your problem. It should be replaced every two years, but really it's for the prevention of corrosion from the absorbed moisture more than anything else.

Edited January 29, 2016 by sparky Paul

[Tim Galaxy Fan]

Thanks Paul, I think you are right about the brake fluid, I did some more reading and when the water in the brake fluid turns into vapour it just makes the brakes spongy, which has never been a problem in this car. Needed a change it fluid in any case which I have now done. I had ordered new pads, (which were jiggered by the problem) and a new flexi. Unfortunately the supplier only delivered the pads, so I fitted these and decided to check out the old flexi by running a wire up it:  it seemed fine. Put the car back together and took it for a short run out before ordering the new flexi, but the  problem started again and only on the OS front brake: LHS was fine, so I'll order and fit the new flexi and try it out again to see if it is the cause of the problem

 

Good point about the ABS sensor I'll take off the sensor and check I removed all the scale but I'm pretty sure I did this when fitting. When I fitted the reluctor ring I noticed the old one had so much corrosion on the drive shaft seat, it had expanded a couple of mm which cut into the old sensor and broke it.  When I fitted the new reluctor, having removed all the scale on the drive shaft seat for the ring, the new ring slipped on quite easily - it was firm enough to prevent turning, and from what I'd read the slotted typed don't need heating to expand them so they shrink fit. Mine was the slotted type but I'm wondering if my old car has experienced so much corrosion that reluctor ring diameter is part of the ABS "warning light on" problem. Possibly the gap needed to generate induction current (between the sensor and ring) is too big.  Anyone any ideas as to the required gap?

 

I'll fit the new pipe and report back.

 

Regards Tim

 

Thanks for all the advice.

[sparky Paul]

I know seating the ABS sensor is a problem because I've had it myself. I found that the air gap has to be quite small, maybe a mm or two. If it's too far away, the ABS fault will not reset. If it's just on the cusp, you get a strange fault where the ABS kicks in during low speed braking, just as you are coming to a stop - but no ABS light on.

 

The flexys can appear fine but still give this fault, for the sake of a few quid it's worth eliminating it as a possible cause.

Edited January 31, 2016 by sparky Paul

[BrianH]

I know seating the ABS sensor is a problem because I've had it myself. I found that the air gap has to be quite small, maybe a mm or two. If it's too far away, the ABS fault will not reset. If it's just on the cusp, you get a strange fault where the ABS kicks in during low speed braking, just as you are coming to a stop - but no ABS light on.

 

The flexys can appear fine but still give this fault, for the sake of a few quid it's worth eliminating it as a possible cause.

 

You can get bits loose inside the hose that move but can't get out - as paul says it isn't worth messing about with it.

 

Failing all else if your still getting the abs light on you should be able to use vcds to have a look at why its coming on, which should narrow down the fault just in case it isn't what you think causing it to come on.

[Tim Galaxy Fan]

Thanks for all the suggestions. I have just replaced the flexi, checked the front brake pistons NS and OS to make sure they are free, and changed the brake fluid.

 

I spoke to a local garage and outlined the problem, the mechanic said if the brakes were binding I should crack the bleed valve and see if it releases the pressure on the brake piston and therefore the disc and allow the wheel to turn freely. As both the front brakes are now binding (OS much more than the NS) I tried this on the OS, and sure enough both the discs (which were binding),  then moved freely I did not have to crack the NS bleed valve. What this shows is that both the NS and the OS pistons are moving as they should and somehow the fluid in them has a common connection somehow. I also lubricated the sliding pins for the brake calipers on both NS and OS but these did not appear to be and issue but both the calipers are sliding freely on the shafts. 

 

I took the time to reseat the ABS sensor and clean every bit of rust off the seat of the sensor. The gap between the reluctor ring and the sensor head is around 0.5mm

 

After putting the new flexi on, bleeding the brakes and re seating the ABS sensor I went for a short drive (2 miles max) the ABS light went off  when I reached 15 mph and I thought I had cracked it, then the damn ABS warning light came back on in another 10 seconds and the brakes started progressively to come on again, when I got the car back home and checked the heat of the disks the OS disc was much warmer that the NS disc and the back brakes were really cold. I had tried not to apply the brakes at all so the discs should not have been warm. I had not burned the pads, but the distance was really short had I driven for longer 'm sure the brakes would have become progressively applied, I did not want to risk any more distance.

 

I am led to believe that somehow fluid is getting delivered to the front brakes that cannot be dissipated. I have not a clue what the problem could be, so am on the verge of expensive garage costs, can anyone help? Mastercylinder or ABS pump/mechanisms???

 

Regards Tim

[BrianH]

Either buy yourself a vcds cable or borrow one, and scan the abs module with VCDS lite. The cables can be had off ebay for a few pounds, vcds lite is free. That will tell you why the abs light is coming on and give you somewhere to start.

 

A Vag-com cable will work - this for example > http://www.ebay.co.uk/itm/USB-Cable-KKL-VAG-COM-409-1-OBD2-II-OBD-Diagnostic-Scanner-VW-Audi-Seat-VCDS-/161717467805

[Tim Galaxy Fan]

Thanks BrianH, I'll get this kit and have a look and reply with results.

[Tim Galaxy Fan]

Hi folks, thought I would complete my tail of woe on the brakes on my MK2 galaxy coming on by themselves back from Jan this year.

 

I really appreciated everyone's help and continue to be a fan of the forum, so I hope the sucessful conclusion of my particuar probem will help someone:

 

As usual with older cars (mine's an 03 plate) there are statistically rare combinations of problems coming on at he same time, which are the most difficult to cure, and this was my case,

 

My eventually found issues were:

 

1) A worn off side cv joint that was moving the drive shaft and ocassionally touching the ABS ring to switch the ABS warning light on. The mechanic ( yes I paid despite my reluctance - but this guy was good) noticed some scuffing on a part of the ring when he inspected it and figured out the cv joint wear. The other side was replaced the previous year. CV off side joint was replaced.

 

2) A faulty electrical connection between the ABS sensor on the ABS unit had to be traced down the wiring loom as the resistance was incorrect and this was the main cause of the problem.

 

3) The NS rear hand brake mechanism (which cannot be refurbrished) was also jamming the brake on intermittently). I replace both NS and OS. My car has done 80,000miles and at 13 years old it's probably one of those jobs that you good folks may need to do at this age.

 

In tracking the probem I replaced: all 4 calipers, the OS brake hose, the OS ABS sensor, the master cylinder and the brake pads - all to no avail, however I have a wonderrful new braking system!

 

I also wrongly reported the issue as both front brakes coming on:  in fact the brakes that came on were the OS front and the NS rear, this, if I'd realised, was a clue to the ABS wiring issue as this is the safety braking system linked to the ABS unit - the front NS and rear OS brakes are on the same hydraulic fluid circuit as are the NS front and the OS rear brake, so in the event of a failure the two opposite side brakes still stop the car in a reasonably straight line.

 

With the incorrect electrical signals being fed to the ABS unit, the unit interpreted the signals and started pumbing fluid into the OS front/NS rear circuit.

 

I'd also like to thank all those that contributed to my issue, particularly sparky Paul and Brian H and for the advice to get vcds download which as luck would have it also works on my VW polo, I can now do a lot of stuff the garage was charging a fortune for.

 

The car drives beautifully and stops like you would not believe!

 

Regards to all Tim

[sparky Paul]

In tracking the probem I replaced: all 4 calipers, the OS brake hose, the OS ABS sensor, the master cylinder and the brake pads - all to no avail, however I have a wonderrful new braking system!

 

Brakes should be good a few years, anyway!

 

Glad you got this sorted, I know how soul destroying it can be when you can't bottom it. Sometimes, the only answer is to start replacing stuff, starting with the most likely... just like most garages do.

[BrianH]

Hi folks, thought I would complete my tail of woe on the brakes on my MK2 galaxy coming on by themselves back from Jan this year.

 

I really appreciated everyone's help and continue to be a fan of the forum, so I hope the sucessful conclusion of my particuar probem will help someone:

 

As usual with older cars (mine's an 03 plate) there are statistically rare combinations of problems coming on at he same time, which are the most difficult to cure, and this was my case,

 

My eventually found issues were:

 

1) A worn off side cv joint that was moving the drive shaft and ocassionally touching the ABS ring to switch the ABS warning light on. The mechanic ( yes I paid despite my reluctance - but this guy was good) noticed some scuffing on a part of the ring when he inspected it and figured out the cv joint wear. The other side was replaced the previous year. CV off side joint was replaced.

 

2) A faulty electrical connection between the ABS sensor on the ABS unit had to be traced down the wiring loom as the resistance was incorrect and this was the main cause of the problem.

 

3) The NS rear hand brake mechanism (which cannot be refurbrished) was also jamming the brake on intermittently). I replace both NS and OS. My car has done 80,000miles and at 13 years old it's probably one of those jobs that you good folks may need to do at this age.

 

In tracking the probem I replaced: all 4 calipers, the OS brake hose, the OS ABS sensor, the master cylinder and the brake pads - all to no avail, however I have a wonderrful new braking system!

 

I also wrongly reported the issue as both front brakes coming on:  in fact the brakes that came on were the OS front and the NS rear, this, if I'd realised, was a clue to the ABS wiring issue as this is the safety braking system linked to the ABS unit - the front NS and rear OS brakes are on the same hydraulic fluid circuit as are the NS front and the OS rear brake, so in the event of a failure the two opposite side brakes still stop the car in a reasonably straight line.

 

With the incorrect electrical signals being fed to the ABS unit, the unit interpreted the signals and started pumbing fluid into the OS front/NS rear circuit.

 

I'd also like to thank all those that contributed to my issue, particularly sparky Paul and Brian H and for the advice to get vcds download which as luck would have it also works on my VW polo, I can now do a lot of stuff the garage was charging a fortune for.

 

The car drives beautifully and stops like you would not believe!

 

Regards to all Tim

VCDS works on quite a bunch of vehicles - Lots of Seats as well as your Polo and other VW vehicles from the appropriate years.

 

Good to hear what the eventual problem (or problems as it was here) was - it helps others out too. Sounds like you've got a mechanic to keep in touch with as well if hes figured that out. Sometimes paying works out better than guessing. Trouble is finding who to pay - My mates work van had an auto electrician out to fix a non-working light cluster (hes fine with mechanical stuff, but electronics he just doesn't appear to get!) . £70 later and it still wasn't working. I had a look and found a burnt off pin in the connector - not something that took particularly long to find. Think it took about half an hour to fix in all and it now works. So it looks like £70 wasted there....