[RamAir02]

Originally Posted by SFV1LE

On a different but related topic, I did notice my fluid reservoir cap would "sweat" and dribble some fluid during track days using Motul 660, which is supposed to be great DOT 4 racing fluid. After I switched to Brembo Racing and Castrol SRF this stopped completely, I assume the Motul 660 was boiling over and the others do not.

Also, I recommend everyone switch to braided SS lines.

I also believe I boiled Motul 660 at the track. I didn't notice any fluid sweating from the reservoir, but my pedal would get pretty long the last 5 mins of a session on track. I haven't had that issue since I switched to Castrol SRF.

[White_1LE]

I had this happen to me on Saturday on my 2019 ZLE. Just the front calipers, but both had tracks of fluid residue coming from the bleeders. I took the rubber caps off and they were completely dry. I had hosed them out with brake cleaner after bleeding the brakes and putting Castrol SRF in. And it has many hundreds of street miles on it since.

So had to be somehow coming through the threads. I did feel like the pedal was a little softer after my first session, but never felt I did not have enough brakes for what I was doing. The main straight at I29 is 140-ish down to 70-ish and the second straight is ~125 down to about ~65 and never felt out of brakes, just a bit softer pedal than I prefer after a few sessions. I put the SRF in last August, then just refreshed the reservoir with fresh stuff before going to the track on Saturday.

I think I will completely remove the bleeders and see how the threads look and go from there. I cannot imagine I boiled the fluid. I have the "Blackwing" deflectors to get more air on the brakes to cool them and it was ~70*. I've broken off enough bleeders over the years to be gunshy of cranking on them too though. Maybe I just need to get after them a little more. I haven't put a wrench on them yet to see if any feel undertorqued. I kind of doubt I put 13 ftlbs on them though. That's actually a lot for bleeder, IMO.

[cdb95z28]

Originally Posted by White_1LE

I had this happen to me on Saturday on my 2019 ZLE. Just the front calipers, but both had tracks of fluid residue coming from the bleeders. I took the rubber caps off and they were completely dry. I had hosed them out with brake cleaner after bleeding the brakes and putting Castrol SRF in. And it has many hundreds of street miles on it since.

So had to be somehow coming through the threads. I did feel like the pedal was a little softer after my first session, but never felt I did not have enough brakes for what I was doing. The main straight at I29 is 140-ish down to 70-ish and the second straight is ~125 down to about ~65 and never felt out of brakes, just a bit softer pedal than I prefer after a few sessions. I put the SRF in last August, then just refreshed the reservoir with fresh stuff before going to the track on Saturday.

I think I will completely remove the bleeders and see how the threads look and go from there. I cannot imagine I boiled the fluid. I have the "Blackwing" deflectors to get more air on the brakes to cool them and it was ~70*. I've broken off enough bleeders over the years to be gunshy of cranking on them too though. Maybe I just need to get after them a little more. I haven't put a wrench on them yet to see if any feel undertorqued. I kind of doubt I put 13 ftlbs on them though. That's actually a lot for bleeder, IMO.

SRF will exhibit "hot compressibility" when it gets very hot. Pedal will soften up a touch but will return to the original firmness when fluid has cooled to (atleast) ambient. I have felt this with SRF and it is a trait among fluids. Some more than others. I noticed this on my Gen5 SS 1LE with ST43 pads. A little softening at the track but when I got in the car the next day for a drive the firm pedal had returned. Boiled fluid will not return a firm pedal. Depending on pad choice, pad construction can "feel" soft at the track when we are full send with the brake pedal, but on the street the pad material is not being compressed as much. Yes, pad material can give or compress under heavy brake pressure. Some pad materials are better than others.

Bleeders do not seal at the threads, it is the taper at the bottom. While you cleaned with Brakleen, it may take more than one blast of it to completely dilute/flush any residual brake fluid. Remember, once the bleeder is closed, there is a column of brake fluid trapped with in the entire bleeder. I have done the BraKleen blast myself over the years but I now use wooden q tips with the cotton cut off to displace the majority of the residual fluid. This pushes most of the fluid out then I lightly clean with BraKleen.

Since there is trapped fluid within the bleeder, there is also residual fluid in the threads. This is a little trickier to completely remove. You can imagine cleaning the threads can be more difficult when the bleeder is installed! More Brakleen blasts will dilute the residual fluid. Also, let the bleeder dry out after using the Brakleen, While Brakleen normally evaporates very quickly on its own, I do not throw the black cap on right after application. I let the Brakleen dry out first.

Any trapped fluid will expand when heated, especially at the track. Street temps don't get anywhere near that of the track. Especially the front brakes. And fluid left in the threads will push out of the treads when the black rubber cap is installed. This has crept up of the years on these cars and I believe its more of a residual fluid issue than a bleeder that is not sealing.

I set my torque wrench to 13 lbs/ft as the GM spec is 13-15lbs/ft.