cully

Hello, I need some help diagnosing

I had my first track event this year yesterday, Stock pads. ATE Typ 200 changed 2 weeks ago, full system flush. My braking performance was poor at best. 15 min into my third session, coming hot into a turn, I hit the brakes and my foot went to the floor so I went strait off track. My brakes were sub-par all day, poor stopping power. I checked the pads and they are fine, like 5mm all around, a little more in front. After I changed and flushed the fluid, the pedal was firm from the top of the range of motion. Now, after the event the pedal is non-existant until about halfway down. The braking performance is poor. There is no leaking anywhere. One thing that might be helpful, a few bleeders were clogged.

Any recommendation? I am going to flush again, to see if that fixes it, If ot. I really don't know what else it could be, so does anyone know what I should check?

Thanks

alabamatoy

Sounds like air bubbles somewhere in or near the calipers. Heat causes the air to expand, making the whole system unpredictable. Otherwise, its possibly time for a new master cylinder.

DocORock

AIR, With out a doubt. You need a power flush.

Nickshu

I have boiled both ATE T200 and Pentosyn SuperDot4 on the track. Neither of these times resulted in any change in pedal feel after the brakes cooled.

I now run Castrol SRF which is the best (almost twice the wet boiling point), but expensive. I would recommend you consider it.

It's possible you damaged the seals in the master cylinder by cycling the brake pedal to the floor which could result in the symptoms you have. Or as said above there could be air in the calipers but unlikely there is air beyond the caliper area after boiling out.

If you do end up needing a new master cylinder the 997 GT3 M/C is a NICE upgrade. See my thread about the installation.

cully

Thanks, guys. Yes I was pretty sure it is air, at least it feels like it. I just didn't realize that I could possibly boil brand new fluid. This track is super hard on brakes though, so it makes sense.

joseph mitro

type of pads could also be the culprit. if your pads are not aggressive enough for track use, you'll put more stress on the fluid and hence overheat it.

Nickshu

+1. My brake caliper temps are remarkably lower running Ferodo DS11.1 vs the Hawk Pro+ I was running before. Checking w/ an infrared thermometer after coming off track.

Kris Murphy

When I first got my 996 I had the same issue. Thought it was air bubbles. Bled, Bled, Bled, and rebled. Also made sure to bleed the clutch slave cyl.. I even purchased the Durametric so I could cycle the ABS pump. All of that did not work. I would make it 10 minutes into a session and the brakes would go soft.

I was running stock pads at the time. At a loss of what else to do, I upgraded the pads, and that did the trick. Not sure if the pads were getting so soft it was creating the fade, or cooking the fluid, but either way, upgrading the pads from stock eliminated the problem.

Paul Waterloo

Please do not run stock pads at a track, no matter what others say. They will just fade as you experienced.

Get dedicated track pads and this will most likely cure your problem and you'll never run out of brakes again.

Additionally, learn to use LESS brake at the track. I once brought my 968 to the track without dedicated track pads and after about 5 laps.....OMG, no braking power!!!

What did I do? On the next session, I learned to use less brake, come off the throttle earlier, don't brake hard, use more momentum, guess what happened? My lap times went down using less brake! Imagine that!

;-)

dkraige

You might also investigate whether any of your calipers are dragging and causing excess heat to build up and boil the fluid. If any particular wheel is much hotter than the rest it would suggest a localized sticking problem like this. If everything is more or less equal temp, it suggests it's a mismatch between your pad compound and your driving style.

I run stock pads and Ate Typ 200 at the track all the time and have no issues, so there's nothing fundamentally wrong with that setup. I have had other brands of pads cause a soft pedal exactly like you describe, and I'm convinced its because they built up more heat and cooked the fluid.

RDL

Paul W is right, learn to drive a 996 as a momentum car. Proper pads and better brake usage will eliminate your problems.

cully

Hey Paul W,

I am running at Blackhawk, pretty sure you might be familiar with it? It is pretty notoriously hard on brakes, especially in door-slammers. Can you give me some tips for using less brakes at that track?

I just realized that I am hi-jacking my own thread...

Slakker

Definitely air in the lines. Upgrade your fluid to Motul600 or Castrol SRF, run track pads for the track, and make sure you have front brake ducts. Tracking these cars is amazing, but it requires a little prep.

cully

Thanks, Slakker. I have been recommended SRF. Which do you prefer? Also, I have been recommended Pagid yellow, which I may bite the bullet and buy. I was thinking about temp-painting my rotors and basing new pads on empirical data,as a few people recommended blacks in the rear for the 996. Do most people use the larger GT3 front ducts?

Definately feel I need to do some brake upgrades, at least fluid, more likely pads as well. I did a full suspension overhaul this winter (coilovers, links, bars, sport alignment settings) and I was running a lot faster at the track, so I assume this is why I had brake problems now, where I have not had problems in the past.

Paul Waterloo

Here's my story from Blackhawk with the 968.....

https://rennlist.com/forums/968-foru...t-weekend.html

I also drove the 996 there once after I got it, had track pads for it.....man, absolutely NO ISSUE with braking.....once you get track pads, you'll never go back. However, I saw my oil pressure fluctuate on the back side of the track on the long left hand sweeper after about 3-5 laps and decided to bring the car in and not chance an oil starvation issue.

https://rennlist.com/forums/showpost...8&postcount=37

I have decided not to track the 996 and just use it as a street car. Sold my track pads to murphy'slaw, who happens to live the next town over, he used them at Road America and had incredible brake all day long!