I'm running Carbotech XP 12/10 pads with Motul 600 fluid on stock rotors. The fluid was replaced by a performance shop last September. I've put about 300 miles on the car since and 4 days at the track (2 in Sept 20, 1 in Feb 21, 1 in Sept 21) and its' garaged. The brakes were fine until the event a few weeks ago. At the beginning of each session, the brakes were fine. About half way or two thirds of the session the brake pedal would get spongy. I'd dial it back to about 5/10 and limp through the remainder of the session. The cool down time between each session was about 1.5 hours. The brakes would be fine at the beginning of the next session then the process would repeat itself. I was running in the intermediate run group on a 90 degree day at Eagles Canyon Raceway which is hard on brakes.

I have a track day coming up but none of the shops in my area have appointments available to replace the fluid prior to the track day. I talked to my performance shop and they told me I probably don't need a full flush and replace anyway but I definitely need to bleed the brakes. He also told me I probably don't have air in the system because I don't have any issues until mid session. He said if there was air in the system, I would have brake pedal issues the entire time. He said the integrity of the fluid has been compromised from boiling the fluid, the wet boiling point is lower now and that's my problem. He also said I need to bleed before every track day to avoid this issue.

Here are my questions: Do you agree with his logic on why air in the system is likely not the problem? I have a Motul bleeder and will follow directions on this forum to bleed. How do I know how much fluid to bleed from each caliper? The entire circuit (until I see clean fluid) or just a few ounces at each caliper? Lastly, can I just bleed the front calipers or do I need to bleed all four corners?

Thanks in advance for the advice!

 

Which fluid are you using? If the boil is an issue, and if you cannot cool your brakes better (e.g. add secondary OEM cooling kit, sold for about $75, if you don't have already), perhaps a better quality fluid would help. Castrol SRF will be one of the best choices available.

IF you have the right fluid and cooling, you shouldn't need to bleed before every event. I don't bleed brakes before every event myself, and it holds up just fine. Also, are you doing cool down before exiting track? It is of utmost importance to not use your brakes during the cool down, since you might end up cooking your fluid, calipers, rotors, pads at the paddock. Just try to use engine braking as much as you can, and go much slower during the cool down, if you're not doing already.

Bleeding is not full flushing. Just removing about a 100ml from every bleeder would do more than enough. If you really cooked the fluid, you'd also see the bubbles stop and the color of the fluid improve as you bleed.

 

I use Motul 600 and flush 2x a year. Zero issues with fade.

Brake fluid is hygroscopic. It absorbs moisture directly from the humidity in the atmosphere.

 

Yes, I always avoid braking on the cool down lap. What about bleeding the fronts only or all four corners? Thanks for the info!

 

It’s been over a year on Motul, it’s time for a full flush IMO. The labor difference between a flush and bleed is negligible, the cost is negligible, and most importantly you know you have fresh fluid only. Is your fluid discolored versus new? Use the color change as an indicator that you have fully flushed each bleeder.

 

thx!

 

My understanding is these high performance brake fluids are only good for one year and then you need to do a complete flush. Even if you do no track days. I am no expert on them though. My 2019 Z06 came with Dot 4 from the factory. I only use that and bleed the brakes every five track days and have had no problems. I bleed eight ounces out of each corner. Four ounces from each bleeder.

 

Motul 660 seems to last about 6 months in my C7 in humid south FL with a few track days occasionly. The fluid turns darker but measures read fine yet I will start to fade towards the end of sessions. Likely more about my poor braking habits and lack of cooling (stock Z51).

I've never measured the exact amount I flush out per caliper but I go thru two 500ml bottles which aligns with what @TJC333 does volume wise.

 

I use Motul 600 and bleed every 4-5 track days and never had issues. I'm in Intermedate group at NCM track. I would do all four corners; why halfway do the job? Motul isn't cheap, but brakes are one area I don't take chances.

 

I bled al four corners! Thanks for the tips

 

Im having the exact same issue as you. LOL like LITERALLY the exact same setup and experience on track to what you are having to the dot. from what i know the xp12/10's are WAYYY too aggressive for the stock setup. my brakes were fine with the 600 and stock pads but once i swapped to the xp12's my brakes **** the bed. Im in the middle of getting an entire brake system swap so i can put this situation behind me and forget about it cause its pissing me off hahaha.

what helped a little was getting the aftermarket cooling ducts that someone else here was talking about but it only delays the problem by a few laps but I still recommend it.