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Discussion Starter · #1 ·
Here is my problem: Any time the temp drops below 25 degrees and my car sits longer than 4 hours I lose my brakes. One of two things happens; the brake pedal is either rock solid and will not stop the car OR on other days it moves but is super slow to return and the brakes stay applied longer than normal, dragging the car. Once the temp rises or the car runs for a half hour the problem slowly goes away. All of the hoses look fine.

Its not the fluid as both front and rear were flushed recently.

Brake Booster? Vacuum issue?

Thanks for the help, could not really locate any info on the web.
-Corey
 

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Discussion Starter · #3 ·
Yes, fluid change was done after problems started. It has done this probably on 7 occassions when it was below 25 degrees at night.

And it is a 2002 v6 4mo.
 

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Discussion Starter · #6 ·
So my mechanic investigated the problem and has told me the ABS control module is faulty. Interestingly there was no ABS light on my dash.... They suggested installing a used one for $350 plus labor.
Does this seem reasonable? Should I do a new one from VW instead?
 

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Get a rebuilt one. What happens if the garage installs it and the problem persists? Are you out $350 plus labor and still no brakes?
 

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So my mechanic investigated the problem and has told me the ABS control module is faulty. Interestingly there was no ABS light on my dash.... They suggested installing a used one for $350 plus labor.
Does this seem reasonable? Should I do a new one from VW instead?
I'm no pro, but i believe you mechanic has no clue.... Maybe i missed something, but i have never heard of a faulty abs module cause problems like this.
 

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Discussion Starter · #9 ·
I guess they ran the vagcom and the only code that came up was something relating to the ABS. Not sure on this one, strange symptoms and have not really been able to find too many similar instances...


I'm no pro, but i believe you mechanic has no clue.... Maybe i missed something, but i have never heard of a faulty abs module cause problems like this.
 

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yes, you can run it without the ABS.

my vote is the master cylinder is hosed possibly two ways - moisture has gotten into the hydraulic oil, causing the peddle to be too stiff at times with the moisture freezing in this cold weather, and the master cylinder needs replaced.
 

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His car is a 4Motion - I'm pretty sure it needs the ABS, as that is what "monitors" the 4 wheels for spin to initiate braking on the spinning wheel(s) which then causes the differential on the front and/or rear axle to lock.
I guess it could run without it, but then you might be running without your 4Motion?
 

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Both the FWD & 4MO can run w/o the ABS, you'll just have "traditional" brakes & no ASR/ESP system.
slammed -- When the car is warm, can you get the ABS system to activate? (try braking hard from 30mph while turning in a wet parking lot). I think you should take the car for a second opinion.

His car is a 4Motion - I'm pretty sure it needs the ABS, as that is what "monitors" the 4 wheels for spin to initiate braking on the spinning wheel(s) which then causes the differential on the front and/or rear axle to lock.
I guess it could run without it, but then you might be running without your 4Motion?
ESP (4MO) & ASR (FWD) use both the ABS system and the throttle to control the wheels. ESP allows for traction and yaw control by firing any of the front and/or rear brakes as needed. Even though the FWD passats have 4-wheel ABS, the ASR system only controls the front brakes and can only provide traction control.

The ESP system has no direct control over the differentials: the Torsen differential in the 4MO/Quattro is completely mechanical. The ASR system only has one differential for the front wheels, and it is completely mechanical, too.

Both systems use the wheel speed sensors (4 total) for feedback, but the ESP system also has a steering wheel position sensor. The steering position data is used to compare "requested yaw" vs. "actual yaw".
 

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Here is my problem: Any time the temp drops below 25 degrees and my car sits longer than 4 hours I lose my brakes. One of two things happens; the brake pedal is either rock solid and will not stop the car OR on other days it moves but is super slow to return and the brakes stay applied longer than normal, dragging the car. Once the temp rises or the car runs for a half hour the problem slowly goes away. All of the hoses look fine.

Its not the fluid as both front and rear were flushed recently.

Brake Booster? Vacuum issue?

Thanks for the help, could not really locate any info on the web.
-Corey
There could be brake fluid INSIDE of the booster. I had this problem on a 2002 Jetta Wagon..
 

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Discussion Starter · #15 ·
slammed -- When the car is warm, can you get the ABS system to activate? (try braking hard from 30mph while turning in a wet parking lot). I think you should take the car for a second opinion...
As the car warms the brake pedal begins to move and has very weak stopping power, not enough to make it safe to drive, but at this point there is no ABS when you hit the brakes hard. It is not until it has really warmed up over a half hour or the temp goes above 30 that the ABS functions. So the ABS is the last thing to come back. I am still puzzled at how the symptoms can be opposite from one week to another. Instead of being like a brick with no stopping power, the brake pedal will move down like Normal, but it does not come back and the brakes stay stuck and then slowly get better as it warms up. It is suspect how cold temps would affect an abs module though.....

Thanks for the feedback, I can't wait to figure this one out.
 
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