problem with brakes

had an intermittent problem with the brakes on me 300tdi for about 3 weeks now an cant find out what it is. brakes work fine most of the time, but once every couple of days il press the pedal and the pedal will vibrate but its like theres something stuck under the pedal so it wont push down (maybe 2cm of movement before it stops hard instead of the normal 7-10cm). the vibration is similar to when the ABS kicks in but slightly more shakey, and when this happens the car doesnt brake. if i press and release the pedal 2 or 3 times the vibration goes away and brakes return to normal. this fault can occur a few times in a row or not happen for 5 or more days, and it happens under all braking conditions - fast stop, slow stop, wet road, dry road, hot day, cold morning.

ive bled the brakes twice (1st time with Disco71 so i know its done right) and there isnt any more air, ive had all 4 wheels off and jetwashed the disks/pads/calipers, ive checked all brake pads are in the right position and not jammed up or anythin, the disks arent warped, the car doesnt pull to 1 side or anythin when this fault occurs, and all the hoses and pipes from the master cylinder out are all in perfect condition with no signs of damage or leaking fluid anywhere. oh and the pads are less than 500 miles old and are all in good condition with no chunks out of them or anythin.

anybody got any ideas what the problem could be and a possible cure?? decided the car is no longer safe to drive untill this is cured, just in case!!

Probably either the ABS pump relay or a wheel sensor playing up and the ABS is cutting in at the wrong time.

my 1st thought was ABS but when i get the vibration it doesnt matter how hard you press the brake pedal the car doesnt really slow down or stop. ive tried to force the pedal down when i get this vibration and its like stamping on a brick but makes no real difference to the speed of the car.

would a fault with the relay or a sensor make the dash light stay on? every now and then the ABS light stays on when i start the car, but if i switch the ignition off then re-start the car the light goes off. and the fault isnt related to if the light stayed on or not.

il get a new relay and swap it anyway, cars a few years old so probably needs doing.

Mark Disco said:

my 1st thought was ABS but when i get the vibration it doesnt matter how hard you press the brake pedal the car doesnt really slow down or stop. ive tried to force the pedal down when i get this vibration and its like stamping on a brick but makes no real difference to the speed of the car.

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ABS is cutting in and stopping you from putting and more pedal pressure because it thinks that you have locked a wheel.

Not sure about ABS light. Some go out once vehicle has reached a certain speed. A Testbook would be able to tell you if there is an ABS fault logged...and I think which wheel sensor if any. Sorry I don't have a Testbook

ahhh makes sense - sounds like your right if the ABS stops you pressing the pedal as the vibration is very similar. il get the relay changed and do the paperclip test on the ABS ECU and see what it brings up. the ABS light should go out when you reach 5mph, but every now and then mine stays on - could be a small stone or bit of **** stuck between the sensor and the shaft so il have another check of that and clean it while im there.

cheers Andy your a star

Hi there, have just seen this post and as i have the same problem was wondering if you found a cure.

not yet

changed the ABS pump relay but its made no difference so tomorrow im gonna read the ABS ecu memory and see what (if any) faults are stored. it seems to be worse when the car is hot and the weather is hot, never does it 1st thing in the morning or in the wet. its also definately ABS related as ive checked all the pads (which are brand new) and theres nothin wrong there, all the discs are ok, and the fault doesnt appear if the ABS is off.

il report back tomorrow after ive checked for fault codes and see if theres anythin there that could cause a problem.

did the paperclip test today and got 2 fault codes .....

2-2: left front solenoid valve (inlet or outlet valve) failure in modulator, wiring harness or inside ECU.

i'd been laning a few days before i started to get problems and had pressure washed the engine bay - removed the wiring plug from the modulator and dosed the plug and modulator in WD40 and gave it a bit of a clean. fault hasnt come back in 10 miles so hopefully thats cured it.

2-14: air gap, left hand front wheel sensor.

light tap round the top of the sensor to seat it right down - fault has not returned.

il be keeping an eye on it for the next week, this was a very intermittent fault so just cause its ok now doesnt mean it'll stay ok

also noticed that the oil level in the swivel pin housing was low on this side, could this be a possible cause of the sensor faults?

Most ABS problems can be traced to wheel slip sensors, the sensor attract iron filings from discs/pads ect, and the sensor cannot 'see' the serations in the ABS ring.

Very very common problem, often shows as air gap issue. If it come back try removing and cleaning the sensor/ABS ring.

regards

Dave

^^^ WHS ^^^

Well done on finding the faults and curing.

Dave 2000 said:

Most ABS problems can be traced to wheel slip sensors, the sensor attract iron filings from discs/pads ect, and the sensor cannot 'see' the serations in the ABS ring.

Very very common problem, often shows as air gap issue. If it come back try removing and cleaning the sensor/ABS ring.

regards

Dave

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code 2-14 came back today along with the grinding brakes/ABS coming on issue. took the sensor out and there were lumps of crud on the sensor so yeah very good advice. not sure if this has finally cured the fault but thanks for the good advice and hopefully this'll be it!!

RAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRR

problem is back again!! but this time there are no faults showing up on the ABS?? the light blinks out and then back on when the ignition is switched on which indicates there are no stored faults, and the light goes out when i get over 5mph which shows everythin 'should' be working ok. but in the 8 miles ive just driven the brake pedal has vibrated under load maybe 15 times. roads are bone dry, the disks arent warped, yet the ABS seems to be kicking in randomly. doesnt seem to matter what the speed is, same problem if i brake from 40 or 15mph.

is this an ABS fault or could it be a sticky caliper? or could there be a fault in the halfshaft or the tractor joint (this was low on oil till the weekend, could lack of oil maybe have caused a fault?)

REALLY need to get this fixed now, cant cope with worrying when im gonna rear-end someone!!

thanks, Mark

Mark Disco said:

RAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRR

problem is back again!! but this time there are no faults showing up on the ABS?? the light blinks out and then back on when the ignition is switched on which indicates there are no stored faults, and the light goes out when i get over 5mph which shows everythin 'should' be working ok. but in the 8 miles ive just driven the brake pedal has vibrated under load maybe 15 times. roads are bone dry, the disks arent warped, yet the ABS seems to be kicking in randomly. doesnt seem to matter what the speed is, same problem if i brake from 40 or 15mph.

is this an ABS fault or could it be a sticky caliper? or could there be a fault in the halfshaft or the tractor joint (this was low on oil till the weekend, could lack of oil maybe have caused a fault?)

REALLY need to get this fixed now, cant cope with worrying when im gonna rear-end someone!!

thanks, Mark

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This is almost certainly a wheel slip sensor. The self check which occurs after starting and then with the light going out and the fault occuring during movement would indicate this is a fault related to wheel speed difference. The fact that since cleaning the sensor has stopped bring up the warning code I would suggest you are on the right track.

It may be worth pulling all the sensors and cleaning them, if one was a mess then the others may well be as well. I have seen this particular fault a couple of dozen times over the last few years and only once has it been the ABS ecu failed.

We were lucky in the garage because we could swap around with known good wheel sensors. Out of all the problems over the years all but two or three sensors responded to cleaning (sensor and the serrated collar) the rest were replaced with new items.

Another strange think that was noted was that on UK rhd cars it was the front left hand front that failed or needed more cleaning. We put this down to it is the first wheel to hit the kerb when parking, the wheel that takes all the sunken drain manholes, and also the one that picked up all the standing water in the gutters, this was never proved but it did seem a little coincidental.

regards

Dave

thanks for the reply Dave. im gonna clean the front ABS sensors again and also drain the oil in the swivel pin housings to hopefully drain out any sludge and crap thats built up in there. is there any way of 'flushing' the swivel pin housing without removing it? or would any flushing agent such as petrol get trapped in there and do a load of damage?

when you mention about cleaning the serrated collar - is this a part of the front CV joint? reading the haynes manual it says that the front ABS collar is a part of the CV and cant be replaced seperately, but the pics aint very clear and ive never been inside a landy swivel pin housing before:doh:. to clean this would i have to remove the half-shaft and give it a diesel clean then refit as it is? or would cleaning the sensors and doing an oil change be enough to clean the area?

thanks, Mark

I have not seen a serrated ring that could be purchased separately but I could be wrong, the norm is with the CV some cars the ring can be purchased on it's own.

Do not put petrol in the CV housing, instead drain out all the oil and refil with 'one shot' grease, this is a 'one off' operation assuming no leaks from the housing seals. If your's are leaking then you might as well strip/clean and replace the seals and then start fresh with 'one shot'.

To clean ABS ring it is best to use a toothpick or similar and through the sensor hole slide it between each of the serrations as you rotate the hub, keep wiping the muck off as you go or you will just move it to the next serration, it is a slow PITA job but if it works it's money saved.

You would not be the first to put the car in a workshop and find that after a hefty bill for wheel slip sensors ect your told "bad luck gov, we found all four sensors were faulty", you then drive down the road and the problem comes back because the ABS rings had bearing/brake/dust/filings on them.

I hope you are lucky and it works, there is nothing worse than a fault that appears and disappears without trace. It is things like this that stop me moving to a newer car, if the fault tracing equipment/software worked it would not be so bad, but your's is a typical example, you have a serious braking fault and the ecu says 'all is well'!!

Good luck

regards

Dave

I had a smilar problem...wheel bearing had a bit of play, all cured with new wheel bearings. I have heard that worn swivel bearings can be the cause.

Dave 2000 said:

I have not seen a serrated ring that could be purchased separately but I could be wrong, the norm is with the CV some cars the ring can be purchased on it's own.

Do not put petrol in the CV housing, instead drain out all the oil and refil with 'one shot' grease, this is a 'one off' operation assuming no leaks from the housing seals. If your's are leaking then you might as well strip/clean and replace the seals and then start fresh with 'one shot'.

To clean ABS ring it is best to use a toothpick or similar and through the sensor hole slide it between each of the serrations as you rotate the hub, keep wiping the muck off as you go or you will just move it to the next serration, it is a slow PITA job but if it works it's money saved.

You would not be the first to put the car in a workshop and find that after a hefty bill for wheel slip sensors ect your told "bad luck gov, we found all four sensors were faulty", you then drive down the road and the problem comes back because the ABS rings had bearing/brake/dust/filings on them.

I hope you are lucky and it works, there is nothing worse than a fault that appears and disappears without trace. It is things like this that stop me moving to a newer car, if the fault tracing equipment/software worked it would not be so bad, but your's is a typical example, you have a serious braking fault and the ecu says 'all is well'!!

Good luck

regards

Dave

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i drained the oil out of the swivel housing yesterday, gave the teeth a clean but there was hardly anything in there, then refilled with ep90. all seemed well then when starting the car after a 2 mile drive the pedal vibrated when the ignition came on and fault 2-14 came back again. i always have my foot on the brake when starting and sometimes the pedal does nothing and other times it either feels like someone punched it from behind or it vibrates for a second. when the fault came up this time tho the 'punch' in the pedal seemed ALOT harder than normal, and the fault relating to air gap came up straight away as soon as the car moved.

so im guessing this is definately a sensor or a sensor ring fault as thats the fault code that keeps on coming up. the sensor does have score marks going across it, i presume from where its fitted into its hole and the ring hits it untill it is pushed to its 'sensing level'? is it common for people to have to replace the CV joint because the sensor teeth go faulty or wear or should i just replace the sensor and see how i get on with that?

Richard Martin said:

I had a smilar problem...wheel bearing had a bit of play, all cured with new wheel bearings. I have heard that worn swivel bearings can be the cause.

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when i 1st had this fault happen i was laning with a few guys from this site and that was the 1st thing they said, jacked it up half way down a green lane to check bearings and all were declared perfect. was having a look round the swivel housing yesterday and couldnt find any play in it at all, was looking at the oil as i drained it and there were no traces of anything metallic in it to say there was anything wearing or rubbing anywhere.

getting to the point where i might just rip the whole ABS system out, becoming more hassle than anythin else now!!!!!

Mark Disco said:

RAAAAAAAAAAAARRRRRRRRRRRRRRRRRRRR

problem is back again!! but this time there are no faults showing up on the ABS?? the light blinks out and then back on when the ignition is switched on which indicates there are no stored faults, and the light goes out when i get over 5mph which shows everythin 'should' be working ok. but in the 8 miles ive just driven the brake pedal has vibrated under load maybe 15 times. roads are bone dry, the disks arent warped, yet the ABS seems to be kicking in randomly. doesnt seem to matter what the speed is, same problem if i brake from 40 or 15mph.

is this an ABS fault or could it be a sticky caliper? or could there be a fault in the halfshaft or the tractor joint (this was low on oil till the weekend, could lack of oil maybe have caused a fault?)

REALLY need to get this fixed now, cant cope with worrying when im gonna rear-end someone!!

thanks, Mark

Click to expand...

Hi Mark, my wife's car was doing the same as yours and sometimes it felt quite unnerving.

So I disconnected the electrical connector on the abs pump and have had no trouble since. Conventional braking (ie no abs) but consistent braking.

I mention this as you may be able to use this information in your diagnostic phase??

Well I had an ABS light on 2-12 error code so I cleaned the offending sensor and took it for a little test drive after and was ok, now today I am experiencing the same issue strangely not on the initially putting on the brakes, but just before I get to a stop the ABS (below 7mph) kicks in when its not needed.

So I'm contemplating my next move so to speak. When I cleaned out the sensor I checked the ring and it looked very clean so I'm wondering how hard is it to replace a wheel bearing or ring.

rcha said:

Well I had an ABS light on 2-12 error code so I cleaned the offending sensor and took it for a little test drive after and was ok, now today I am experiencing the same issue strangely not on the initially putting on the brakes, but just before I get to a stop the ABS (below 7mph) kicks in when its not needed.

So I'm contemplating my next move so to speak. When I cleaned out the sensor I checked the ring and it looked very clean so I'm wondering how hard is it to replace a wheel bearing or ring.

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That's in autodata:

code:
2-12 Wheel speed sensor, RH front-air gap > Probable cause : Wheel speed sensor, sensor rotor, wheel bearings.


Swap the front sensors....if after that u get the same code it's the bearing/rotor if u get 2-14 it's the sensor