Braking problem - malfunctioning ABS

ChrisSlicks

I appreciate the brainstorming, it is really odd behavior.

Did some more testing today at lunch as the weather conditions were similar to the weekend, sunny and warm near 80. I mostly used the same roads repeatedly to rule out surface conditions.

The results were that the first few stops were great, like face through the windshield great. I did a couple of laps around the block between each stop to cool things down and even out the heat. After stop 5 things started to go downhill, gradually getting worse each stop. The pedal still feels solid, but something is happening to make the ABS think the surface is loose as you can feel it push back hard on the brake pedal as the fluid is pumped back the other way.

At this point I'm pretty convinced it is somehow heat related, but I'm just not sure how.

davidyan

As the temperature of the fluid increases, the pressure will increase while applying the brake. (although it will not always translate to higher braking power)

One possibility, is that the hot fluid and high pressure is triggering your emergency brake assist system. Maybe a little far fetched but wanted to throw it out. Most brake assist systems trigger based on the speed at which you hit the brake but could it also be somehow linked indirectly to brake fluid pressure? Also, the ABS sensor also detects brake pressure which could be thrown off by the high temp.

alan93rsa

What you are describing is exactly what happened to me at Putnam Park in the S2000.

At Mid-Ohio with the 370 I ran the stock pads with Motul RBF 600. No brake fade but the laps were limited due oil temps issues.

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JeepTodd

I have seen some weird brake problems, very similar to what yo are seeing, that are from a tiny air bubble in the ABS system itself. I am told you have to bleed the brakes with the ABS cycled open. The ABS cycle is different for every car. The easist way is to have a dealership computer cycle it. Otherwise there should be some sequence of things you can do to cycle it open.

ChrisSlicks

Thanks guys.

I'm taking it to the dealer in the morning, see if they can cycle the ABS controller and pop that bubble outta there.

ChrisSlicks

I took it to the dealer this morning but the technician was unable to reproduce the problem, which isn't altogether surprising. He's going to talk to Nissan engineering to get their opinion but somehow I think I'm going to end up on my own.

I'm going to bleed the brakes with the car running and see where that gets me. I'm going with the ATE Blue fluid for now.

wstar

Without a computer hooked up that can talk to the ABS controller, you won't be able to properly bleed an air bubble out of the ABS. There are tools available that can do it for most cars, it's kinda like hooking up an OBD-II code reader (same socket), but the tool talks via CAN to the ABS computer and can instruct the ABS to purge itself, etc. This tool: Actron® does it for ~1996-2005 domestics, but probably doesn't cover our car. Or you can just have the dealer do it.

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ChrisSlicks

Yeah, I was afraid of that. Unfortunately I think I'm going to have a hard time convincing them to bleed the brakes even if I offer to pay for it. They're acting all suspicious now, the service writer walked around the whole car checking it out, looking for what I don't know ... signs of abuse maybe? I drive my car hard but I don't abuse it.

cossie1600

Ice mode, happens to the C6 a lot too

RCZ

Yeah this happened to all of us who track the car hard, even with upgraded rotors and pads I remember someone went into ice mode.

I think Travis no longer goes into ice mode...because he has AP Racing 6pots....

simple fix i guess haha

travisjb

As RCZ mentions, with my AP Racing BBK I am not getting any of this... and I definitely had it before - I remember 'icing' my way towards a wall at Phoenix Intl Raceway !!! not something that is easy to forget... can someone verify where they abs sensors are located ? I suspect with the stock setup there is heat being transferred to the sensors which is throwing off the ABS computer... with my setup, heat is dissipated much more efficiently... yes $$ to upgrade... but sh1t- why take chances on brakes! here's a thread on the apr kit AP Racing Big Brake Kit Installed!

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2009 370Z #104
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import111

I still not only have not had this issue...but quite the opposite. The hotter my brakes get the better they stop me. Other people have ridden in my car and driven it and they agree that the stock brakes on my 370Z are insane and stop hard as hell.

travisjb

they are good brakes, until they overheat. come on up for the september nasa event at PIR and i'll show you exactly how it works

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bullitt5897

I have experienced the "Ice Mode" before too... Its a creepy feeling especially on the street when you need to drop 30+mph to make the turn LOL. I learned to let off and re-engage the brakes and it goes away. But dont worry I will have Alliance 8 Pots 15" 2 piece rotors real soon! I cant wait for the slam your face into the windshield braking... The sport brakes are good but these Alliance brakes are going to be the Sh1ts! I will post up pics and reviews when they are finished and come in. I am starting with 8 piston front and after those are done they are going to make my 6 piston rears!!!

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boosted180

has anyone measured any temps to see at what point this happens? i'm going to an auto-x this sunday and will try to get some readings. but at a typical auto-x, the brake temps may not go up enough to cause the problem. will see.....