What Brakes

[Tonka73]

Hi all

Looking for a little help with my 06 plate 130TDi trendline Passat last of the old shape.

The car is at the main dealer but they cannot find any problems hence I am here.

The problem is:

3 ish weeks ago brake warning light appear then disappears ( must take car to garage I think! then Christmas)

between Xmas and new year pedal feels real odd with the travel changing.
I checked the brake fluid which appear fine a little low maybe but fine.

Booked the car in at the dealer

On the way home night before the visit the pedal travel got really long, really really long, panic time at the trafic lights but it did stop!! Hand brake on which was at close to 90 degrees loads more than usual. Set off to get out of the way and everything back to normal, so steady home (not far).

Taking car to dealer following morning nothing all fine!????

Any ideas!

thanks Tonka

[calum]

Sounds like a big problem,but the car is an 06 so it's VAG's problem to fix, thanks to the warranty.If they start getting shirty with you,tell them it's the number one safety feature on the car.They have all the diagnostics equipment so they should be able to pinpoint the problem quickly.Probably an ABS pump problem,seems to be quite common,anyway good luck with the car,Cheers Calum

[Tonka73]

Thanks Calum

Have got the car back and they claim to have done nothing. However the car feel and runs a little different.

I am thinking that they have changed some settings? Maybe updated the over complicated computer system that all modern cars have these days.

I don't understand why they may have changed something and not said, however my experience with VW dealers it that they are in a little world of their own.

I will run the car for a few days and see what happens

Will update in a week or two if I don't have any serious issues (optimism is a wonderful thing)

[RickT]

nothing in VAG can be changed for the brakes!!!

I would guess there was a leak on the system somewhere and they have replaced it without telling you.... (which is not right)..

if they claim to of not done anything like that... take it easy for a while or even book it into another VW dealer to check... (as you know... we all need brakes!!)

RicKT

[Teutonic_Tamer]

I've had something similiar with my B6 S4 a while back, with a very long brake pedal going near to the floor with the engine running, but maintaining a "normal" travel with engine off and no servo assistance.

Having done some work on the brakes myself, I actually feared that i'd either srewed up the master cylinder, the ABS modulator or the servo.

Backtracking right upto the starting reason for working on the brakes in the first place.

Took the car on a track day, and regularly smoked the front brakes, with onlookers commenting on my cherry red glowing discs. Towards the end of the day, in my determined desire to beat a B7 RS4, I cooked the brakes very badly, with the pedal going down to the boards, and looseing virtually all braking effect, which resulted in a minor wing-and-bumper-to-track-bollard-interface (but that's another story). With the front tyres looking like Formula 3 slicks and the canvas very visible, it was end of play for the rest of the track day.

A host of other commitments meant my S4 was off the road for 4-5weeks (wifes new car/holiday/powdercoating rims/new tyres etc). I eventually got round to stripping the front brakes down (including disconnecting brake pad wear and wheel speed sensors), cleaning all the guides, applying fresh ultra high temp anti seize paste, and refitting everything.

I then started bleeding the brakes, and wasn't surprised to find a lot of air in the fronts, due to boiling the fluid on the track day. What did surprise me though was just how much air was in the fluid, along with the fact that just one circuit seemed to be affected - the front-right and rear-left just would not bleed clear, while the front-left/rear-right bleed clear very quickly. Going round checking the tightness of all the brake pipe & hose unions, I found some very slight give in the spanner on the top of the ABS/ESP modulator for the bothersome FR&RL circuit (confirmed after checking up on my German to English translation), although it was only ½-1 flat on the nut . . . Anyhow, after trying a couple of different bleeding techniques, pumping through 2½-3 litres of fresh fluid, I finally got rid of all air, and a nice firm short travel brake pedal finally resulted.

After firing up the motor, with the aid of jump leads due to a flat battery, the brake pedal merrily proceded to sink to the floor. Pump away to restore normal pedal travel, but no joy. Kill the motor, pump the pedal a couple of times to get rid of the stored vacuum from the servo, and bingo a normal short travel brake pedal again. Fire up the motor again, and pedal down to the boards again. After double, nay triple, finally quadrupley <sp?> checking all components for any signs of leaks or other damage, and confirming all OK, I thought along the lines of a ******* servo.

After an intensive brake test on my usual <cough> closed roads, the brakes are mighty efficient, pull up in a perfectly straight line, at varying pedal pressures, even under max pressure with ABS merrily buzzing the pedal - conclusion, the brakes work perfectly OK, just a bl00dy long pedal.

Much head scratching lead me to my local trusted independent garage. After plugging in his mighty expensive Snap-On fault code reader (what an awful, useless piece of junk that was), a number of fault codes were retrieved and then all deleted (or so I thought!!!). The significant (to this brakes issue) codes were both front wheel speed sensors (intermittant error), and low battery voltage. The low battery code is obviously self-explanatory, the wheel speed sensors may have triggerd the fault code when I disconnected them, and turned on the ign whilst disconnected.

Driving away after clearing the codes resulted in a normal brake pedal travel. I can only think that the stored fault codes for the wheel speed sensors, which supply data to the ABS/ESP, somehow caused the brakes to go into a kind of "limp home" mode, with the very long pedal travel acting as a permanent warning/reminder to get the brakes sorted.

The OP may merely need to get any stored fault codes cleared.

Rgds