Inconsistent brake pedal at track

I've posted over at RX-8club, but figured you guys could help too. not sure if its an RX-8 issue or something to do with ABS equipped cars. Here's a copy of my post. Any help guys?

Car: '09 R3 Brake Pads: Carbotech XP-12 Front, XP-10 Rear SS brake lines ATE Super Blue fluid - full flush and bleed Stock tires Brake pedal height has been adjusted to the highest point.

TSC/DSC is OFF (Button held for 8 sec., both lights on)

I'm instructing at Grattan raceway this weekend. It's the first time I've had the car on the track and it's running awesome except for an inconsistent brake pedal feel.

Sometimes the pedal is nice and firm with good feel. I am not getting into the ABS at all. It is in a good position for heel/toe downshifting.

Other times it gets a long pedal and drops below the throttle pedal. It never fails to stop though. Again, I am not getting into the ABS. The ABS is working fine, though because I can feel it kick in occasionally.

It is also not pad knock back. I make sure to pump the brakes a couple of times before hard brake zones just to be sure I have brakes. When I get to the brake zone, sometimes the pedal is firm, other times, not. Always slows down though.

I bled the brakes at the track and there was no air. Pad wear was fine.

So that is what is happening. Any ideas?

Thanks in advance!

How are you bleeding your brakes?

If you aren't using a pressurized system (The bug/garden sprayer thing) you might try that.

Sounds like a bad master cylinder. I just had mine start to go about a month ago (~68k miles on the car, '06 RX-8). Similar symptoms. I checked around the MC and could see a tiny line of etched paint coming down the booster where the cylinder had just started leaking a little. I was surprised it gave up at only 68k, but I really beat up on the brakes on that car.

I've seen something basically similar happen with a bad ABS pump. Given, it was a Honda Accord, but it would occasionally need a pump of the brake to fill the ABS reservoir (or whatever it's called) back up with fluid, then the brakes would work fine until the pump had had time to bleed down again. JY ABS unit fixed it.

Are you sure your ABS is ALWAYS working? Any weird sounds from it?

EDIT: Uh, yeah. MC is probably more likely than the ABS pump... ahem.

Well, it looks like you guys were right about the mastercylinder. I seperated the master cylinder and booster and a bunch of brake fluid came out. Then the pedal got really long in the paddock. So i'll nurse it home and get it to the dealer next week. Thanks for the advice!

Happy to help. Make sure you bench bleed the replacement MC really well. I didn't when I replaced mine, and now I've got more travel in the pedal than I'm happy with. I'm going to have to spend some more time bleeding it later this week as a result.

Question for you - when you experience the long pedal symptom, do you feel kind of a crunch like it's pushing through some kind of barrier? This is what I'm experiencing.

Mine will be going to the dealer to have this taken care of under warranty.

Funny thing is, when I bought the car, it had the master cylinder leak trail down the booster. I had them check it and they said it looked like someone spilled fluid. I doubt they tested it at all. And now it has failed. I'm just glad it wasn't at 115+mph into turn one!

No crunch right now, but it does groan a little bit.

Argh...why don't they believe me?

Rant warning!

Dropped the car off at the dealer this morning. I explain the situation and what I had found. I get a call at noon. No problems. I tell them that is not acceptable, did they check the master cylinder? They call at 3 and tell me there are no visible leaks, and the car drives and stops fine. (BTW, the brake pedal feels worse than my old '99 C2500 mushy pedal).

I go to the dealer to get some stuff from the car that I needed. I ask to speak to the tech. Tell him the whole story, show him how far the brake pedal travels and how it feels mushy. He gets in, "Feels fine to me". At this point I tell him, again, about the MC leak. "I'm not allowed to take anything apart." I'm firm but polite and explain that I'm not accepting the car until they visibly inspect the seals of the MC. I leave the car with them. I get a call from the service manager, and explain everything....again. Says he can't do anything without confirmation of the complaint. At this point I'm banging my head against the wall. I showed them the pedal travel. I told them about the MC leak. I call the GM of the dealer (who I know from when he sponsored me a bit when racing SpecMiata) and leave a message. he calls back, and I explain everything....yet again. He explains the warranty situation to me etc. I said I would agree to pay for the diagnosis, and if anything was found faulty, I wouldn't get charged. Now I have to wait to hear back to see if they can do that. Rant off.

Am I in the wrong here? I know I know more than the average joe customer of theirs and I'm being as polite as possible when working and explaining ot them, but I was also getting very frustrated.

Thanks!

That's aggravating, I know. But here's the deal: the warranty at 68k is the service contract company, not Mazda.

The SC says the customer is responsible for ALL diagnostic up to the point that the problem is discovered, then the SC is contacted and they decide whether it's covered or not. Covered part = reasonable diagnostic covered, not covered part = diagnostic not covered.

Now, here's the deal: disassembly is not covered, as you were told. So if the tech doesn't find anything wrong, disassembles something and still finds nothing wrong he doesn't get paid. Yeah, I know that ain't your problem. But that's how it works.

Not only that, if he disassembles something, doesn't find anything wrong, puts it back together and sends you on your way then you get killed in a crash on the way home, his family's attorney can claim he contributed to the accident.

Or if you demand that a part be replaced and the condition still exists, the SC washes their hands of the whole thing and the tech/dealership are on the hook.

Yeah, he's stuck in the middle. He's going to err on the side of caution and I don't blame him.

Thanks. I completely understand where they are coming from but it does suck. My car has 16k miles though and still under 3/36 Mazda warranty. So i thought diagnostic would be covered too. Thanks for the clear explanation. I just hope it is covered for everything.

Got a call. They said the master cylinder was dry. Im lost because i know what i saw. I guess i'll see how it feels when i get it back.

I'm at my wits end here. Picked the car up, pedal the same as before. took the car to my non-dealer trusted mechanic. I just told one of the guys, drive the car and tell me what you think of that pedal. He drove around the parking lot, pulled back in and said, "what, that mushy pedal?" It also turns out, they ahd an RX-8 in the shop. I was able to compare brake pedals. It felt like a proper brake pedal in that car. Got home, rechecked the MC. Fluid out the back. And the pedal is getting worse. ::banging head::

So, GRM brain trust, if you take a MC off of a booster, is there ANY possible reason for fluid to come out from the back of the MC? Am I nuts?

HELP! How do I deal with this? My next step is going to take the car back, and make them take them MC off in front of me. However, they aren't happy with me right now, and I'm not happy with them. This sucks.

Sorry for the long posts. I am just extremely frustrated with this whole situation.

It's under a Mazda warranty?

According to your profile, you've got an unfairly long drive to any of three dealerships.

Take it to a different one.

I ended up taking the car to a different dealer. Wow, what a complete turn around in customer service! Not only did they listen to me, they let me talk to the tech before he touched the car, and they explained everything to me very clearly. Then they checked the car, and found the problem right away (I was right, it was the MC), and will be replacing the MC and brake booster. I have a loaner car until parts come in from Japan. An engineering rep. will also be looking at the car since this problem hasn't been seen before. And the customer service rep. will be talking to the original dealer service department as well. I'll update once the car is fixed and back in my hands.

Thanks for all the advice and being a great sounding board!

happy ending

Glad it worked out!

And whoops, I thought for some reason the car had 68k on it. My mistake. Under 'base warranty' which is what your car is under, everything is always covered including diagnosis.

EDIT: JohnnyHachi's car is the one with 68k. Oops.

Got my car back! 100x better in the braking department. If you're in need of service for a Mazda in SE MI, go to Brighton Mazda. Excellent customer service and they have an RX-8 specialist as well.

The original dealer (who will remain nameless since they did support my racing in the past), still denied me a refund for any diagnostic charges, but Mazda Customer Support did come through and are refunding my money.

CGLockRacer wrote: Got my car back! 100x better in the braking department. If you're in need of service for a Mazda in SE MI, go to Brighton Mazda. Excellent customer service and they have an RX-8 specialist as well. The original dealer (who will remain nameless since they did support my racing in the past), still denied me a refund for any diagnostic charges, but Mazda Customer Support did come through and are refunding my money.

thank you for posting who you took it to for good service. I suspect that the service on my Miata was done at the same place you have been to, and it was pretty crappy.

Brighton Mazda is a little bit of a hike, but all things considered, worth it.

(but I probably need to go to an independant place in AA, anymore....)

Alfa - You've got PM.

CGLockRacer wrote: Alfa - You've got PM.

Uh, haven't gotten it... just so you know....

In reply to alfadriver:

I'll try again...i think it said it bounced from your email as spam.