2004 Passat Brake issue?

[Riknos]

Hi All,

Driving the Passat the other day, went to brake and when pressing the pedal nothing happened, it was rock hard, and I had to basically stamp on it to the floor to roll to a slow stop, after a few minutes of this and nursing it the way home it magically started working again fine?

Any ideas?

I recently changed the front discs and pads a week before, I didn't drain the excess fluid straight away so the car had over max brake fluid for a while,

I jacked the car up and spun all the wheels independently, one of the front wheels has resistance even when in neutral (it's an Auto) is this normal? is this due to the diff? The other side spun fine. The rears sound like they are catching, possibly warped discs both sides so going to replace those too, but if a caliper is stuck could this be causing the brake issue or is it going to be something else?

Appreciate any advice, thanks.

[Prizam]

Riknos said:

Appreciate any advice, thanks.

Don't piss about with brakes unless you know what you're doing.

My guess is a hydro lock. this happens when the fluid flows backwards and the slave has not fully released.

Bleed the system, top down. Preferably using the pedal and not a pressurised bleed kit. try to rewind the pistons fully before starting this.

[The Wookie]

Did the pedal go hard or did it drop to the floor?

The former might suggest a failing vacuum servo or pump if it came on suddenly, the latter might be a dragging caliper that’s boiling the fluid

[Riknos]

The Wookie said:

Did the pedal go hard or did it drop to the floor?

The former might suggest a failing vacuum servo or pump if it came on suddenly, the latter might be a dragging caliper that’s boiling the fluid

Rock hard, like the engine had cut out but it hadn't. My google results pointed me to the servo but would it be an intermittent issue? wouldn't it fail or not?

I also assumed the dragging rear brake may be boiling the fluid but wouldn't this cause the pedal to be soft not hard?

[The Wookie]

Riknos said:

Rock hard, like the engine had cut out but it hadn't. My google results pointed me to the servo but would it be an intermittent issue? wouldn't it fail or not?

I also assumed the dragging rear brake may be boiling the fluid but wouldn't this cause the pedal to be soft not hard?

You would have thought so but it could be something like a check valve failing and intermittent because you happened to hit the brakes at a moment where there wasn’t much vacuum.

As you say, boiling fluid would make the pedal long. The pads could have overheated which would make the pedal go harder but a rear brake on a FWD car id expect it would be pretty undramatic

[yellow cento tom]

I had the same thing happen to me in my passat a couple of weeks back, quite unnerving one of the vaccum lines running along the bulkhead had popped off so re attached and all was well. Hope this helps

[carboy2017]

my mates Golf (54 reg) had the same issue and apparently it was a hose from the servo from what he told me he had a close shave on the A31 when the brakes refused to work !

[Riknos]

yellow cento tom said:

I had the same thing happen to me in my passat a couple of weeks back, quite unnerving one of the vaccum lines running along the bulkhead had popped off so re attached and all was well. Hope this helps

carboy2017 said:

my mates Golf (54 reg) had the same issue and apparently it was a hose from the servo from what he told me he had a close shave on the A31 when the brakes refused to work !

Very interesting, thanks guys. I'll inspect all hoses tonight, but the car was working fine afterwards so suspect a hose hasn't just popped off but maybe related to the servo. When I did some Googling a lot of posts reported to the brake servo failing after the blocked drain hole problem which I had circa 1 year ago, so perhaps the brake servo has damage to it since then?

Edited by Riknos on Monday 2nd July 15:14

[Mammasaid]

If it's a B5.5 (longitudinal engine), I wouldn't rule out a rusted servo from the dreaded plenum chamber issue that affected all Passats, A4s and A6s from that period.

http://www.vwaudiforum.co.uk/forum/showthread.php/...

[E-bmw]

As above it is almost certainly either vac hose or servo related causing leaking away of the vacuum.

[jon_273]

I had this once when I borrowed a B5.5 Passat not too long ago. Went to brake for some traffic lights and there was suddenly no servo assistance. Luckily I had left a decent gap! After that incident it was fine and never did it again.

It was a likeable car despite it trying to kill me and leaving oil on the drive. You could say it had character.

[Riknos]

jon_273 said:

I had this once when I borrowed a B5.5 Passat not too long ago. Went to brake for some traffic lights and there was suddenly no servo assistance. Luckily I had left a decent gap! After that incident it was fine and never did it again.

It was a likeable car despite it trying to kill me and leaving oil on the drive. You could say it had character.

I hope mine does the same!

Upon further research it definitely sounds like the vac /servo didn't work, but it's fine since so not sure what would cause it to be tempermental?

The brakes on the passat have always sucked and they got no better when I fitted new discs and pads so assume it's leaking anyway potentially?

I guess it could have a constant leak and just had a brief moment where the pressure wasn't enough?