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Discussion Starter · #1 ·
Chronology:
- Last week my stock brakes (Coupe with Z06 Pads) had wonderful bite (engaged strong and immediately) and feel but on the occasional back road they would fade, and I had never once bled the car with 52k miles.
- In preparation for my first DE I decided to beef up the stock system knowing that if I had fade on little back roads that the track would be a nightmare. So the day before the event a knowledgable friend and I installed:
1) DRM Goodrich SS Lines with -3AN Connectors
2) DRM SS Pistons with new dust boots and piston seals
3) Full Flush (including friend's Tech2) with ATE SuperBlue
- no bubbles came out that we noticed (we've bled them a TON, took the rubber mallet to the calipers, bled them in both the normal and reverse order on the wheels, used the Tech2 and Snap-On tool to bleed them, etc)
4) SS Speedbleeders (fit was very snug)
5) New NAPA Rotors
6) Used Stock Z06 Pads (my carbotechs never came in)

As soon as the car came off the lift from this work, the pedal feel was no longer as good as it previously was. The brakes worked, but the big difference was their bite was completely gone. The performance was moderate, and could engage ABS with enough force, but the pedal went much further down to get good braking performance. Note, this change happened on the lift, not after a track day. We also bled more, switched the pads, switched the rotors, and still had the exact same symptoms.

The DE was a blast, but the brakes just didn't hold. They were spotty all day and never really held and got worse as the day went on (i could only get 2 laps at IRP (easy on brakes) before fade). Oddly, the biggest decline in performance at the DE was after the brakes cooled off.

Cliff's Notes:
- good brakes
- added mods listed above
- lost bite and had much longer pedal travel before brakes engaged
- had fade issues all day at DE
 

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Did you bleed the brakes hot?

Did you get brake fluid on the pads or rotors?

Did you bed the new rotors? New rotors need to be bedded in before track use.

Were the new rotors deglazed? Manufacturers sometimes use an oil or silicon on the rotors to stop rusting in shippment and while on the self. I recommend using CRC Brake Cleen spray to remove any film on the rotor faces and I also recommend using a fine grain sand paper or 3M Scotch Brite on them prior to use.

I would also recommend bleeding hot and using the moodified 3 step procedure recommended by Chevy. IE
1. normal bleed,
2. then ignition ON and wait 1 minute and rebleed,
3. then ignition OFF and rebleed
This clears the system solenoids not associated with the ABS

Race pads will make a difference. It could be the old pads were glazed or tapered to the old rotors.

Also check your master cylinder fluid level to be sure all the new caliper piston seals are not leaking. A small fluid leak at the piston seal will cause the symptoms you describe.

Are your calipers tapered or spread? You may need new calipers if so.

My recommendations at this point are to:
1. Deglaze and lightly sand the new rotor faces
2. Rebleed HOT using the 3 step procedure
3. Install race pads and bed the pads in.
4. Throw the old pads away.

If the problem still exsists then I would start looking at the caliper piston seals and then look at the calipers themselves to see if they are spread (top to bottom) or tapered (front to rear)
 

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Discussion Starter · #3 ·
DJ, thanks for taking the time to walk through this with me!!

I did not bleed them hot initially, but 2 days after the DE I did, without any change in pedal.

I doubt I got an fluid on the pads or rotors, and I have tried two sets of pads and two sets of rotors with no change in pedal.

I did not deglaze the new rotors, but the pedal feel was the same with both new and old (deglazed) rotors.

Good idea on the 3 step bleed. We may have done this (my buddy was kinda telling me what to do...so I can't recall all bleed details), but I'm not sure. We've bled them quite a few times. Can you expand on what solenoids are cleared via the 3 step procedure? Anything that the Tech2 wouldn't have taken care of?

I doubt it was pads, since the brakes were strong before putting it on the lift, and weak after the work was done. If the pedal went bad after the DE, I would agree that I should look at my pads. For the same reason, I think caliper spread and pad taper can be ruled out.

We looked under the dust boots for leaks. Correct me if I'm wrong, but even a mild leak would leave the area between the piston seal and the dust boot full of bright blue fluid. I couldn't perceive any change in the master cylinder level.

I agree to looking at the master cylinder, we haven't and I think it's the #1 suspect right now. Any advice on how to approach it, or get air out of it easily?
 

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Do not always trust tech2. Try this: Go back to stock bleeders. I have had problems on occasion with sped bleeds not allowing me to get a rock hard pedal. Put the key on bleed from the furthest wheel from the MC. If you hear the ABS pump shut the bleed screw down and proceed with bleed after th ABS pump stops. Do this for all wheels and let me know what happens. In theory DJ is correct about seasoning bedding in rotors and pads. I race and never do this because my car is on a trailer and I can't go rip around on the streets. When I'm on the track I am "on the track". i have never suffered Green fade etc... So while yes there is absolute proof that DJ is correct in reality maybe guys like DJ can feel it but to me it is a waste of time and has never helpped me nor have I ever experienced poor brakes because of it. If this does not help and you really did everything right then swap back to the stock brake lines and report back here. I have never heard about SS line probs on C5's except throwing codes but on occasion there is something wrong in ss line manufacture that causes poor flow and you get funky pedal feel. With SS lines you should have a harder more positive pedal not a soft longer pedal travel
 

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Discussion Starter · #5 ·
Sounds like the SS lines are not at fault, and we did a pretty good job draping them away from everything to avoid arcing. I cannot see any value in changing back to stock.

Nor can I see why changing the speedbleeders out would help. If they were allowing air in, wouldn't this same air get bled out? We haven't seen any air bled out thus far. Maybe I'm just not following you per se...can you explain why a speedbleeder would cause me to lose my bite and have a long pedal?

I agree with you on the beding comments.
 

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BQ,
I have raced for a time now and fixed cars including engine rebuilds gearbox etc.. since I was 16 mostly on porsches and ferrraris. I own a Z06 but quite frankly it is such a good car I have never ripped into it so I do not know all the nuances of how its systems work. So my statements are generic. If you are not a "real" mechanic then you are flying by the seat of you pants like the rest of us. The problem is that you made 4 changes at the same time, pads,rotors,lines,bleeders. And these changes can effect other parts of your system too. When you do mods or repair for that matter you will have greater success if you make one change at a time so that you can adequately monitor the success. So now you have no idea what's wrong. That means you need to too 10times more work and work backwrds by process of elimination and or have a fresh pair of eye look over your work. Additionally, you are no longer stock on the pads and rotors and you this may be how that new set-up is. Some say the NAPA rotors are china crap. At 20bucks I can't even buy raw steel for less. Also, if you used your old stock pads you can screw your rotors when you put new carbotechs on if you damage the rotors with the stock pads. Some very agressive drivers and do significant wear to rotors in only a few DE sessions. Try DJ's or my bled technique first then dump the speed bleeders and rebleed in no good. Then revert back to the stock lines . All of this assumes you have the technical ability to diagnose new or unseen caliper leak or master cylinder leaks. Also, I just reread your post you put new SS cylinders in thats 5 changes and those also could be the problem if they are hanging up or not moving smoothly they will stick and cause fade and screw your pedal modulation. The wrong size piston can change your pedal travel. So now you can add that to the list of going back to stock to find your problem.
 

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I've had the best luck just doing a nice, slow gravity bleed starting with the wheel furthest away from the master cyl - the RR and working your way around. Do that, some good SS lines, new pads and rotors and you should be set once you bed the brakes and rotors in. If that doesn't do it, your calipers have probably spread and need replaced. You can get them for $105 though so it's good insurance. I replace mine twice a year. It's very easy to do.

Oh, I've never used the Super Blue, but you may want to try the Motul 600. I've raced on it for two years now and haven't found anything as good for the money!!!! It's $11 per bottle...and absolutely no fading.
 

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A few suggestions,
- Look very hard for a leak from all the stuff you changed. A very small leak will give a soft pedal. As mentioned above, I couldn't get my speedbleeders to seal properly and took them off.
- Bleed again.
- Change your pads and bed them in if you can. Your old pads may have been tapered and you are just noticing it now.

If that doesn't do it, and you don't think you have another problem, like master cylinder, I'd suggest new calipers. I only get about a year out of mine before they are spread enough for me to notice more pedal travel, even with new pads.

As an aside, I agree with Chris that Motul is great, but I switched to a new fluid from Wilwood (American company) with the same cost/performance as Motul, the EXP 600 Plus.

Both Motul RBF 600 and Wilwood EXP 600 Plus have higher wet/dry boiling points than ATE Superblue. Note: none of these fluids meet DOT 3 warranty requirements. Be careful taking your car to the dealer if you still have a warranty with the blue stuff in it.
 

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Is there a way to measure the caliper to see if they spread? I think I ran into a similar thing with stock Z06 pads and glazed the heck out of the rotors and burnt through the rear pads (They went Metal to Metal) and burnt a dust boot on one of the rear calipers.
Thanks
 

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Subdriver said:
A few suggestions,
- Look very hard for a leak from all the stuff you changed. A very small leak will give a soft pedal. As mentioned above, I couldn't get my speedbleeders to seal properly and took them off.
...
- Change your pads and bed them in if you can. Your old pads may have been tapered and you are just noticing it now.
...
Both Motul RBF 600 and Wilwood EXP 600 Plus have higher wet/dry boiling points than ATE Superblue.
Used pads from a different car? I think subdriver is pretty much spot on. I also ditched the speedbleeders on my race car (8 of them).

The 600s are all good fluids. Motul is the best deal.

You may have a sealing problem with your new pistons in your old calipers. However, the other things are much more likely.
 

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Discussion Starter · #11 · (Edited)
Figured it out...

Used my old pads vs the stock pads I've been driving on. It wasn't pads. It wasn't speedbleeders either. No way caliper spead or glazed rotors could have been it considering the chronology. Piston seal leaks would have been pretty obvious from my experience.

I got it figured out tonight. 2 problems:

1) Air in the master cylinder. Bench bled it and the pedal came back up to where it used to be.
2) More interesting, the brake booster vacuum hose was too close to the headers and had collpsed upon itself. It caused the pedal to go firm intermittently depending upon engine vacuum. I'll try to capture some video to show exactly what happened.
 
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