passat brake pedal movement

[welling]

I have a 54 reg passat tdi 130 highline auto with just 20,000 miles.............the brake pedal basically goes to the floor !!! ( I bought it at 16.,000 miles from VW dealer and the problem was not evident then )

the brakes actually work, but the movement is very worrying........


the first diagnosis was rear pads 70% worn, so they were then replaced, but no improvement


the VW dealer says the pedal is "normal" and acceptable, but I say this cannot be right, especially as my previous 2002 passat diesel auto did not have this problem...................furthermore , if they are saying it is"normal", then by default they are saying that when the car was brand new, the SAME pedal movement must have been there ??? ...I don't think so ?


there is no fluid loss, but you can definitely hear and feel some pressure loss when the pedal goes to the floor.........is it a bypass issue ? is the master cylinder at fault somewhere ?


this pedal movement cannot be "normal " !!!

[Stevebt]

Hi
Sounds like air in the system to me.

[welling]

cheers Steve, but today the VW dealer tested car again and they still say nothing wrong..........they say it is normal....................I am awaiting VW head office intervention..................this cannot be right,,,,,,,,,,,the dealer actually confrimed that when the car was brand bnew it would have had the same brake pedal to to the floor action...!!! I think not !!

[motman]

Hi,
Info From The Dealer Could Well Be Correct.
Many Modern Diesel Engined Non Hgv Vehicles Are Now Fitted With "high Boost Servos" And Vacuum Pumps. This Prompted The V.i. (now Vosa) To Issue A Special Notice Sighting Spicifically Vauxhall (but Applicable To All, Sn 5/94 And Sn9/95) Advising Mot Testers Not To Fail These Cars Just On Long Pedal Travel!

A Quick And Reliable Test, With The Engine Off Pump The Brake Pedal Several Times To Exhaust The Vacuum In The Servo. Now Apply The Pedal Hard Down, Normally It Will Reach A Stop Long Before The Floor, Now, Does It Creep? If It Does Creep Or Reach The Floor Get It Checked, If All Is Ok, With Your Foot still Hard Down, start The Engine, You Will Feel The Pedal Drop As Vacuum Pump Evacuates The Servo And Continue To Drop Slowly With Each Pump Revolution. This Is Normal.
On The Road The Brakes Will Lock (but For Abs) Long Before The Pedal Travel Became An Issue.
Bit Long Winded But I Hope It Helps, Cheers.

[john250]

Hi guys,

I've got the same problem with my wife's S reg 1.9Tdi. we've had it from 8 months old and we're both sure that the pedal travel has increased recently. I particularily notice it when I switch over from my own car. I've checked the pads n disks and they are only about 25% worn and all working ok, I've replaced the master cylinder and bled the system completely but still no improvement.

Its not a nice feeling when you're comming to a roundabout and the pedal goes almost to the floor. The brakes do stop the car but you don't feel as if you have anything in reserve as the pedal is about 1 inch off the floor. With the engine off its a good hard pedal but with it running there's almost no resistance to pressing the pedal.

Its gotten to the point where neither of us are comfortable driving the car because we're expecting the brakes to fail completely.

Cheers

John250

[Eddie]

Had a problem like this years ago but the car had done 120000 miles the flexi hoses on the brakes had softened up and where expanding under the pressure of the braking system,worth a look

[passat 130 tdi]

after changing rear discs and pads and bleeding all 4 calipers i find the pedal ok - its not my ideal brake pedal for me . It does get better with 3 pumps of the pedal though .

as going to the floor i'd say mine goes to half way before my head hits the screen .

i definately think you may have an air lock somewhere . i also read that when screwing in rear caliper pistons , the returning pressure from brake fluid back to the resovoir can turn the master cylinder seals inside out causing brake loss.

try pumping up the brake pedal with the engine on , 3 pumps and the pedal should be hardish , if not you have issues.

i also hear a "schooosh" sound on depressing the pedal , mainly when the engine is off though . HTH ?

[john250]

Hi Guys,

Don't wish to hi jack this thread, but I've now replaced the hoses to the calipers as Eddie suggested and I've still got a long pedal. Basically its made no difference whatsoever. I've also tried the brakes with the handbrake on by one notch, thinking it might be stretched cables allowing the pads to retract too far but this made no difference either.

To my simple way of thinking, whatever is causing the problem has to either be a problem with both circuits or a component that is common to both circuits. Otherwise you would expect that if a component on only one circuit (say a caliper) was faulty the other (good) circuit would give you a good pedal because it would react normally.

Any / all brilliant suggestions would be welcome, because I'm running out of ideas.

Cheers

John

[Eddie]

I said check the hoses not go and do em regardles two man job one pumps the brakes the other watches the hoses, anyway other possibilities passats have sliding calipers have the sliders seized? are your discs worn excessively,an old trick we used years ago was to take up the play on the pushrod that actuates on the master cyl piston 2 locknuts inside driver bulkhead not sure if this is applicable to Passats though,check the one way valve on the vacuum to the servo is it one way? check the 'o' ring on the servo vacuum inlet,check servo for water ingress,when you changed master cyl did you bleed in the correct order ie furthest from master first.

[john250]

No problem Eddie, the decision was mine based on the fact that I had already replaced one hose due to a pin hole. All calipers are sliding freely, discs n pads show more that 70% life still on them. The impression I get is that servo leaks would produce a hard pedal, the problem I have is the opposite.

Doing the test described by motman gives a hard full pedal with the engine off but pressing the pedal hard when the engine starts the pedal goes to within 1 - 1.5" of the floor. Having said that when simulating an emergency stop I can bring on the ABS on a dry road but that is with the pedal finishing near the floor. As I said the brakes work but its the "J C" moment when the pedal goes so far down that's very unsettling.

I'll try adjusting the push rod on the servo to see if I can take up some of the movement.

Thanks for your help.

Cheers

John