Brake Pedal Issue long throw on first application

[fuzzystig]

Hey folks, I've got a brake issue that's been racking my brain a bit. I've got a 2002 GTS, so an ABS car.

When I'm driving, the first brake press results in a long brake pedal throw. After this initial long press, the subsequent brake presses feel great again. Whats odd is after one 'braking session', if I wait a few minutes and apply them again (like driving on the highway and braking only every few minutes), it's the same thing. First brake is long, then it firms up great. If I'm driving on a curvy mountain road where I'm using the brakes a lot, the brakes feel great after the first press. Kinda feels like pad knock back maybe?

I've re-bled the system using a motive brake bleeder (I've bled my brakes a hundred times on all my cars, always without issues). Ted May at Valaya just recently replaced the wheel bearings less than 200 miles go, with new OEM units. I just got new rotors from JonB (again, OEM), so I don't think I have any wobbly rotors (either from wheel bearings, or warped rotors) causing the pads to knock back.

I did notice some dried-up residue on my brake booster, right under where the master cylinder mates to it. It looks really old though. If it was easy to get a replacement master cylinder, I'd just swap that out but it seems this part is tricky to find. I'm not very familiar with the master cylinder nor the brake booster - is there a seal I can replace in there that seals up against brake fluid somewhere? I found a master cylinder to brake booster seal, but my understanding is that just seals the vacuum, not the fluid.

My other thought is maybe I have air in my ABS pump somehow.

So my question to you folks is: based on my described symptoms, do y'all think it's likely I have a damaged master cylinder? If so, anyone have any recommendations on repairing or replacing this? And if not, do you folks have a recommendation on bleeding the ABS block?

Thanks in advance!
Anton

[Dan Cragin]

Hi Anton,
On a ABS car you need to actuate the ABS pump while bleeding the system. This is done with a scanner that actuates the system.
This most likely is your problem.

Hope this helps.

[Steve-Indy]

As Dan said, it takes a scan tool. When Tom Sessions and I held our week long service sessions (13 in all) at a friend's CDJM dealership, ONE of my jobs was to be the pedal pumper...clutch and brakes.

On ALL ABS Vipers (2001-2006 and 2008-2010), another of my jobs was to cycle the ABS system using a DRB III during the brake bleeding process...just following the protocol on the screen.

I am not sure if there are cheaper, more available tools on the market now to do this outside of the realm of CDJM dealerships. If anyone knows of same, please post the info.

[Dan Cragin]

Typically this process is not needed unless the system has lost quite a bit of fluid, but it sounds like this is the issue with your car.
Your Dodge dealer or a brake shop should be able correct the issue.

[Old School]

Kinda feels like pad knock back maybe?


Have you tried applying the brakes a couple times, maybe a minute apart, in the driveway not moving to eliminate this possibility?

[fuzzystig]

Woah, lots of help from everyone! thanks folks.



I'm gonna get my hands on a scan tool and run through the procedure, regardless. I'll also check Old School's suggestion of running the car in the driveway and seeing what it does. Ya'll rock!

[goggles Pizano]

If you ran the master dry/low, air entered the ABS unit or you somehow introduced air. The cheap $100 or so scanners will not have the ABS bleed function. You need to use one that has that function but i would check the master too.

And the master is easier just to buy one and rebuild the stock one but you will be the one sourcing the seals for use. i bought a reman one and will rebuild the stock one one of those days and post seals etc. I already pulled it apart.

[dave6666]

Don't be such a pussy. Go hit the skid pad, Wal-Mart parking lot, school zone or whatever, and activate the ABS system to push the air out. No programmer needed.