ABS brake failure / fault

We are having major problems with our ABS brakes on our 95 300TDI ES.

The ABS light is on all the time and the brakes intermittantly fail (usually at low speeds).

We have had it hooked up to the diagnostic computer at the friendly local garage, who advised it showed up as needing a replacement ABS ECU module. It also went up on the ramps, and was thoroughly inspected for faults/damaged/misplaced/dirty ABS sensors, but all seemed OK.

We have today put on replacement ABS ECU module purchased for £20 from LR breakers, but the ABS light is still on all the time. Although the brakes haven't failed since fitting the ECU module we still don't trust it as the brakes often work fine for a day or so and then go on to fail several times in one outing. Does this mean that the replacement ABS ECU is also faulty, or, that other replacement parts are needed, OR, does it just need resetting on the computer to get the blooming ABS light to go away!

We have been advised that it is definately a problem with the ABS, not the servo, as failure problems would be there all the time, and also not the vacuum pump as the brake pedal is hard before starting and goes softer when starting the vehicle - which apparently is how it should be?

To describe the symptoms of the intermittant brake failure - it mostly fails at low speed (usually under 15mph, and mostly shorly after starting up). When pressing the brake pedal usual resistance is felt, but when brake failure occurs you feel the pedal pump a bit and a gravely feeling the brakes just do not work no matter how hard you try and push!, usual brake pedal resitance remains.

We have had the brake fluid replaced and this has made no difference. (The stuff that came out was really bad, very VERY dirty and full of air).

:doh: We love the disco, but are getting very worried about it's lack of reliable brakes!!!! - please help if you can. Thanks

Shaz, you're in luck. I've had exactly the same problem. I can tell you that you most probably have a wheel bearing that's got a bit of play in it. The sensors for the abs are effected by the wheel bearing and when you feather the brakes at slow speed the abs cuts in (the vibration you talk about). Once the light comes on the ABS is disabled and the brakes work ok. So, for less than 20 quid from Paddocks you're sorted!
Hope this helps

Mark

I have the same problem (check out my threads), my bearings are fine, ive had to take the ABS fuse out in the end (until i can get the problem sorted), you lose ABS but at least no russian roulette braking! If you want to check if the ABS is now working and that the light is just on (you may need it reset) just drive somewhere with 2 wheels on the grass and 2 on the tarmac at about 10 MPH and brake sharply, you'll soon find out!
Bloody ABS - bit of a dark art.

landymangib said:

Shaz, you're in luck. I've had exactly the same problem. I can tell you that you most probably have a wheel bearing that's got a bit of play in it. The sensors for the abs are effected by the wheel bearing and when you feather the brakes at slow speed the abs cuts in (the vibration you talk about). Once the light comes on the ABS is disabled and the brakes work ok. So, for less than 20 quid from Paddocks you're sorted!
Hope this helps

Mark

Click to expand...

The wheel bearings all seem OK. The ABS light is on at ALL times, it never goes out at all. Do you know if we can completly disconnect/remove the ABS and revert to normal brakes - would this then pass an MOT??

Unfortnately, if it leaves the factory with ABS then it will be checked at the M.O.T.

I have the exact same symptons as you, and an impending MOT too.

Please post the remedy should you fix it in the next couple of months.

regards Red.

redhotmax said:

Unfortnately, if it leaves the factory with ABS then it will be checked at the M.O.T.

I have the exact same symptons as you, and an impending MOT too.

Please post the remedy should you fix it in the next couple of months.

regards Red.

Click to expand...

We are hoping to look into it a bit further this pm, so will let you know if we manage to get anywhere with it!

Update..... we have had it plugged into the diagnostic computer again, and the replacement ECU unit is OK. The ABS light went out for about 3 miles, but then returned. The final fault that is now showing is front left wheel sensor wiring - so we are gonna make another trip to the LR breakers and get a replacement sensor & wiring - fingers crossed this should then be OK. Will post more when we know.

Shaz said:

The wheel bearings all seem OK. The ABS light is on at ALL times, it never goes out at all. Do you know if we can completly disconnect/remove the ABS and revert to normal brakes - would this then pass an MOT??

Click to expand...

pull the fuse out and you will have normal braking again (no ABS) to pass an MOT however you will have to have a friend who does MOTs who will look the other way or alternatively you could wire the ABS light up to your oil light and hopefully fool the tester - hypothetically speaking of course

Hi... a further update for you.

We have finally got rid of the ABS light and intermitant break failure!! - yipeeee!! (and no, we haven't taken out the bulb or fuse!)

With the help of our local friendly LR specialist garage (£20 diagnostic check) we appear to have fixed the fault. As well as a replacement ECU (£20 LR breakers), we also replaced one of the front sensors, which was what was showing up as an intermitant fault on the diagnostic test. It wasn't the sensor itself, but the wiring from the senor, so although visually it appeared to be ok it was further down the line. We went to the LR breakers again and got ourselves a sensor c/w wiring for £10, fitted it and so far so good.

The ABS light comes on as it should on starting the disco and goes out around 5mph..... AND WE HAVE BRAKES!! (which is quite a novelty now!)

It's well worth doing some homework to find a local friendly garage who live and breath LR's! - Their knowledge and experience is fantastic and they charge a fraction of the price that main dealers charge.

Hope this helps you if you are having similar problems - good luck.

Now..... next job......attempt to get the central locking to work!

:crazy_driver:

congrats.. I know my abs problems were not as severe as yours but it is a good feeling to get that little blink when you turn the key .. and my heart still leaps a little every time I hit 5 miles an hour and the light goes out..

happy driving

Hello,
I have a problem with my ABS system too.
The problem started couple of months ago. My sister was driving the car (discovery I 300 tdi XS 1996) while she was coming to the stop sign the ABS got activated; Few days later the car went for a regular service and when we told the mechanic about the incident, he suggested to flash the braking system. For couple days everything was functioning properly.
Then this is what happened:
1. Weird clicking noises were coming from the valve, the one that’s close to the ABS
pump; We replaced the valve.
2. The Master Cylinder developed a leak; replaced that too.
3. I cleared the contacts of the master (engine bay) fuse box.
4. Yesterday, the mechanic lift the car up and checked for anything loose; bearings
etc; nothing was found.
5. We use a computer to talk to the ABS computer; the result was wide gap and
open circuit on both front sensors; we tried to clean it, but……
6. Yesterday when I refueled the car I noticed that the weight was making a
difference the brakes were working better and no light; weird
7. Even with the ABS light on the ABS function SOMETIMES.

All this is very strange to me. The petal is kicking randomly. Any suggestions?
Regards,
Stelios

Out of interest do LR still produce new sensors and wiring for the disco 1 or are we now scouring the net and breakers yards for bits and pieces...

The sensors are easy to get hold of new . Both genuine and aftermarket, they just cost lots more . Regards Jonathan