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Discussion Starter · #1 ·
Hi, I am having problems with my abs. When I am driving say at 40 or 50 mph and I apply the brakes hard the abs kicks in quite badly and I dont stop as quickly as I should. I am new to driving TTs so am not sure if this is normal but I would have thought that braking hard at a fairly low speed should not activate the abs in dry conditions. I have had new discs and pads fitted, new abs sensors and new brake fluid. My brake servo is on its way out but dont think that has anything to do with it.
If anyone else has experienced any problems like this or has any ideas please let me know. cheers
 

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gaz16 said:
Hi, I am having problems with my abs. When I am driving say at 40 or 50 mph and I apply the brakes hard the abs kicks in quite badly and I dont stop as quickly as I should. I am new to driving TTs so am not sure if this is normal but I would have thought that braking hard at a fairly low speed should not activate the abs in dry conditions. I have had new discs and pads fitted, new abs sensors and new brake fluid. My brake servo is on its way out but dont think that has anything to do with it.
If anyone else has experienced any problems like this or has any ideas please let me know. cheers
If you can get a VAGCOM scan, it might pin point a fault in one or more ABS sensors or indeed the brake system in general.
If you didnt have the problem before you changed the sensors, then its likely to be related to them.
Were they genuine sensors that you fitted?

When you changed the fluid, was it done with a pressure bleed kit or at the dealer?

Have you got any warnings on the dash, like the ESP or ABS light showing permanently?

Does the pedal vibrate when the ABS kicks in?

As for the brakes not being as good as before, thats likely to be just the pads bedding in, as mentioned in the previous post. They do take a while to settle in when new.
 

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Discussion Starter · #4 ·
Hi, thanks for the replies. The problem was there before all the work was done on the brakes. The pads and brake fluid were done by an audi specialist garage, the abs sensors were changed by me.

I was getting the esp and abs lights coming on together not all the time but quite frequently. I had it tested on VAGCOM at an audi garage but there were no faults being picked up for the abs or braking system but when it was checked the lights for the esp and abs wouldnt come on.

The esp and abs light still comes on periodically I have tended to notice them coming on more often at higher speeds. I do also get brake pedal judder when the abs kicks in which lasts for some time.

There seams to be a gremlin in the system somewhere but cant find it. I am hoping that next time the dashboard lights come back on I can get it plugged into a VAGCOM and hopefully get a fault show up then.
 

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Its a very strange one for sure.... with no codes appearing or a clear diagnostic result makes it even more strange.

I hate to say it but it could be the actual ABS control module, not the pump but the electronics that control it.

Unfortunately the controller isnt sold separately and a whole new ABS pump is all you can get from Audi but theres a firm called 'ECU Testing' in the UK that can repair these (i think).... they repair dashpods and ECU's, and have an excellent reputation.

The thing is, if the module was faulty or there was an error in the speed sensors, wiring or the brake fluid pressure sensors, you would almost definitely get a fault code stored and therefore you would see it in VAGCOM...... :?

Do the ABS & ESP lights stay on for any length of time or only when the actual pedal vibrates?
If they only light up when the ABS is running or the pedal is buzzing under your foot, then that indicates its working correctly and therefore no codes would be thrown up.
However..... if there was something wrong with the position of a sensor or something wrong with the surface of the stepped rotor on the hub, which shows the sensor that the wheel has locked etc, then that might be telling false info to the ABS unit and activating it too early...... if you see what i mean.

If you can, try to have a real good look at the rotor on each wheel hub, if necessary, remove the sensors and check they are the right or the same distance from the rotor.
If theyre sitting too far away from the rotor it will get a weak impulse, plus ive heard of people having issues with dirt collecting on the tips of the sensors causing false ABS operation.

I hope you get it sorted without too much aggro....
 

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Discussion Starter · #6 ·
Cheers for the help,

just going back to what you said about the lights on the dash coming on when the abs is running and the brake pedal vibrates, they dont come on or flicker when the abs is kicking in, they just randomly come on every now and again and stay on until I restart the car.Which makes things even more weird.

I will have a look at the sensors and wheel rotors at the weekend and get it plugged into VAGCOM when the lights appear again and hope it gives me a fault code.
 

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Thats the best bet for now for sure.

I had something similar on my 225 after i bled the brakes and stupidly let the resevoir run dry.... got air in the ABS unit and this caused the ESP and ABS lights to stay on..... but i had a very spongey pedal too, despite more bleeding.
Finally had the fluid changed at Audi and that sorted it.....
I wish this was the same as your problem but i think if you had the brake fluid changed by a good indi, then thats fairly unlikely.

Good luck with this, ill be very interested in the outcome of the scan and hopefully the resolution.
 

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Discussion Starter · #8 ·
Finally fixed. So I was getting the abs kick in at low speeds also I was hearing a strange sound as well like a twanging noise when breaking at low speeds. This noise went when I pulled the abs fuse out so it was something related to the abs system. Having checked and changed all the wheel speed sensors and checking the rotors for any damage and having the brake fluid changed and bleed by an audi indi garage I decided to have the abs module checked by ecutesting.com. I found a specialist garage in Rugby called Vasstech who removed the abs module and sent it to be checked. However the unit was returned having been checked as ok. Vasstech refitted the module and checked out all sensors, wiring etc and believed that it must be the abs module at fault. I purchased an abs module from ebay which was then fitted but the problem still existed to a certain extent. They then re diagnosed with vagcom and it showed a fault code for the longitudinal sensor. This sensor was changed and the car was fixed, my brakes now work. I am not sure if the problem was the abs module or the longitudinal sensor or a combination of both but I am glad the car now stops as it should.

Vasstech in Rugby very recommended, they removed my abs module,sent it out for repair, refitted it spent two hours checking out abs system, diagnosed it twice with vagcom, fitted a second hand abs unit provided by me. All this for 500 notes which included the cost of sending the abs out to be checked.

Thanks for the help and advice and I hope that this helps someone else as it proved the be a real headache for me.
 

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Sorry, bit late now, but you can monitor the sensors in VCDS/Vag Comm, Select Module, ABS, Measuring Blocks, MVB 4, 5,& 6. I think 6 is the Longitudinal sensor. They should all be steady around zero +/- 4 or 7 depending on sensor. You can watch them change if you rock the car turn the wheel and push the footbrake. It's in the WAK guides and on the RossTech site. Seems as if you may have had an ABS issue as well (possibly poor connection cured by removal refitting etc) because a faulty Longitudinal Sensor should only affect ESP and not ABS.

Glad to hear it's sorted though. :D
 
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