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View Full Version : B5 A4 Flashing Brake Light; Brake Fluid Reservoir Full



shysell
02-19-2014, 06:45 PM
I've been looking around for some clues to solve this but I haven't found anything that fits my situation exactly. My car was on jack stands for 8-ish hours while working on it - nothing brake related - I got the wheels back on and went to go for a test drive - the brake pedal went to the floor twice. Third pump, I had a pedal. Low on brake fluid, was my first thought. Checked it, the reservoir was full. The red light started flashing. Had a buddy watch the reservoir while I pumped the brakes and the fluid went up and down with the movement of the brake pedal (Is this normal?) We kinda think it is the master cylinder but I've been reading that the ABS module failing would cause the same situation (For the most part) - Thing is my ABS has been in-active for 2 years because of a broken wheel sensor connection. Could it be the brake booster? My pedal will be solid after a pump or two; before that it is a little spongey but definitely stops the car. Any thoughts about what this could be, couldn't be would be appreciated. Thanks in advance for reading and the help

MetalMan
02-20-2014, 08:42 AM
I wonder if one of your rubber brake hoses has a bubble or something.

There could also be air in the ABS system. This requires VAG-COM to fully bleed it out.

shysell
02-20-2014, 09:22 PM
There could also be air in the ABS system. This requires VAG-COM to fully bleed it out.
Thanks for the reply!!!!!!

After discussing this thoroughly with a buddy, I realized that the blinking and beeping only happens after I move the car and get above say 25mph. We kinda fell on the idea of the parking brake sensor going bad. The sensor has 165k on it (if you can measure that on it) and I use my brake daily. With it only costing $10 I thought it to be worth a shot. I just ordered a new one. If this doesn't help I'm going to give a Motive power bleeder a shot and see what happens.

Has anyone else encountered something like this???

How does VAG-COM help fully bleed the brake system? This is a first of me hearing about it, but I am still kind of green when it comes to knowing a ton about these cars. Every new experience is a learning one for sure!

ianwpb
02-20-2014, 09:27 PM
Thanks for the reply!!!!!!

After discussing this thoroughly with a buddy, I realized that the blinking and beeping only happens after I move the car and get above say 25mph. We kinda fell on the idea of the parking brake sensor going bad. The sensor has 165k on it (if you can measure that on it) and I use my brake daily. With it only costing $10 I thought it to be worth a shot. I just ordered a new one. If this doesn't help I'm going to give a Motive power bleeder a shot and see what happens.

Has anyone else encountered something like this???

How does VAG-COM help fully bleed the brake system? This is a first of me hearing about it, but I am still kind of green when it comes to knowing a ton about these cars. Every new experience is a learning one for sure!

You can cycle the ABS pump, or something like that with VCDS.

shysell
02-20-2014, 09:40 PM
You can cycle the ABS pump, or something like that with VCDS.

Ok, cool! I'll definitely look into that. I'm still going to install that sensor and see what happens. I'll make my next move after what transpires from that. I'll keep everybody posted with my findings, what I break, fix... get pissed at etc.


Thanks for the help thus far!

MetalMan
02-21-2014, 08:00 AM
Yep, VAG-COM allows you to run the ABS pump, which in combination with a Motive Power Bleeder, will allow you to fully bleed the ABS system. I only got air into my ABS system because I let the fluid reservoir run too low... if you didn't then there probably isn't air in there and normal bleeding should be sufficient.

Mad Cow
02-21-2014, 09:14 AM
Why would you just buy a handbrake switch out of the blue? You know you can test these things, right?

MooseWhip
02-21-2014, 10:19 AM
Is it the red BRAKE light on the dash or a yellow brake light on the LCD thats on?

shysell
02-23-2014, 05:27 PM
Why would you just buy a handbrake switch out of the blue? You know you can test these things, right?

I didn't just buy a hand brake switch out of the blue. I've talked to a few mechanics that I know and after some talk with it being the cheapest option and it made sense to give it a try, but it didn't fix it. Also, I'm not sure how I would have tested it. Bright side though, I now have a brand new OEM handbrake switch and one thing that I can mark off the possible problem list.

It is the RED brake light, not the one to let my dumbass know to change my pads. The fluid level is good and there isn't a leak I can find - that's another reason why I went with the switch first.
My pedal is fine and it stops my car without any problems. As far as I can tell, I do have brakes. With a wheel speed sensor that has a break in the line (no connection) the ABS module shouldn't be working. It has been this way for the past 2 years. Would the ABS module still be receiving signals and trying to work with both rear wheel speed sensor disconnected? If anyone has any other idea, my ears are wide open.

Thanks for all the replies guys. This is definitely helping out.

shysell
02-23-2014, 05:39 PM
Why would you just buy a handbrake switch out of the blue? You know you can test these things, right?

If you could go through how a guy would test these things, that'd be great. Maybe you have the key to figuring out what exactly is wrong.

Has anyone used www.cheapabs.com? Any user reviews would also be great to read.

Mad Cow
02-23-2014, 07:45 PM
Get the ABS unit scanned, no use in guessing (as you've likely just learned). Also use that vagcom to cycle the ABS pump like others have said. The handbrake switch can be tested just like any other switch, test for continuity between the 2 points with a multimeter and press/release it to see if the reading changes.

walky_talky20
02-23-2014, 07:57 PM
^Yep. Or (for an intermittent problem) bypass it with a piece of wire for a few days to see if problems go away.

That said, I believe the behavior of the BRAKE light upon Low Fluid or Handbrake Engaged condition will be solid ON. Not flashing. Flashing indicates a different problem. Usually that the cluster is unable to communicate with the ABS module (ie: due to it being failed in most cases). This can be intermittent - some days no flashing, other days flashing. There are tiny connections in the module that are the failure point, and they can make and break connections whenever they like.

The diagnosis steps would be to connect to the ABS module and Instrument cluster with VCDS (formerly known as Vag-Com) and look for codes that indicate a communication issue. Note the codes that appear and clear them. Create symptoms again and re-check codes in both modules.

*BAM* >> Diagnosis.

Then send your module to that one guy who is reportedly awesome (http://reflecttuning.com/shop/index.php?main_page=product_info&cPath=1&products_id=1&zenid=aee04e99dab330030ab085c2234ef64b), and your problems are solved.

frozenpuppy
02-23-2014, 10:11 PM
Light flashes when fluid is way too low. Test the low fluid sensor on your reservoir. Google the resistance specs

shysell
02-24-2014, 04:59 PM
Light flashes when fluid is way too low. Test the low fluid sensor on your reservoir. Google the resistance specs
That's definitely worth a check. Especially when it only happens when the car is moving.

brakebleeder
08-04-2017, 10:38 AM
I've been looking around for some clues to solve this but I haven't found anything that fits my situation exactly. My car was on jack stands for 8-ish hours while working on it - nothing brake related - I got the wheels back on and went to go for a test drive - the brake pedal went to the floor twice. Third pump, I had a pedal. Low on brake fluid, was my first thought. Checked it, the reservoir was full. The red light started flashing. Had a buddy watch the reservoir while I pumped the brakes and the fluid went up and down with the movement of the brake pedal (Is this normal?) We kinda think it is the master cylinder but I've been reading that the ABS module failing would cause the same situation (For the most part) - Thing is my ABS has been in-active for 2 years because of a broken wheel sensor connection. Could it be the brake booster? My pedal will be solid after a pump or two; before that it is a little spongey but definitely stops the car. Any thoughts about what this could be, couldn't be would be appreciated. Thanks in advance for reading and the help

Maybe try a reverse brake bleeder.

Nollywood
08-05-2017, 01:35 AM
Light flashes when fluid is way too low. Test the low fluid sensor on your reservoir. Google the resistance specs

If the fluid level is correct, a faulty level sensor still wouldn't account for the brake pedal dropping to the floor, and require pumping a couple of times, to lose the sponges feel.