So what is the stock fluids dry boiling point?
I really don't want to flush before and after each track day to maintain my warranty if I dont have to.

 

Then don't. Most C7 owners don't switch back to Dot 3 like the OM instructs for most of the years. Just like they didn't switch from 15W50 oil every time they came back from the track.

As we know from Tadge's response to the question asking for the reason why GM said to switch back to 5W30 for the street was more about GM fuel mileage certifications and increased catalytic converter warranty costs Vs an engine damage reason.

I suspect something like the stock fluid probably holds a lower moisture level and is less likely to corrode brake parts that are exposed to the fluid. That was the reason GM instructed people to switch back to Dot 3 on the C7.

Bill

 

So I must not be getting this right.
My assumption is that following the track prep guide to the letter is the key to keeping your warranty intact. Is that correct?

If so then changing brake fluid back and forth after each event is one of the things you are required to do (and prove) to keep your warranty?

Thanks!

 

Yes and no... GM recommends what they recommend due to liability. They want you to have a very high temp race fluid in for the track so you don't boil the fluid and trigger the new brake by wire fade warnings etc. They then want you to revert to DOT4 for the street for moisture capacity. The street fluid can absorb more water which would protect the components. However, if you're doing a few events and changing fluid that often the fluid will always be very fresh. Fun fact... one of the best racing brake fluids you can buy is Castrol SRF which has a wet boiling point over 500 which is higher than many fluid's dry boiling point. It's also labeled as a DOT4. So... you meet all the rules. It's got a dry boiling point over 590 that GM specs for the tack and it's technically a DOT 4. Downside is it's really expensive stuff.... like $65 a bottle on Amazon.

 

Unfortunately, SRF is $90 a bottle when you can get it now days.

 

Anyone know the capacity of the C8 Brake system? Normally 1 litre is sufficient for a change as I recall the entire system in a C7 was well under a litre. What is your experience? I am having the dealer put Castrol SRF in at $150 Canadian dollars per litre I don't want any to go to waste.

 

Late to the discussion....A lot of the convoluted bleeding process (particularly the full system one) is when you actually have air in the system and need to get it out for sure.

If you never let air in the system in the first place and only want to flush old fluid out and new fluid in, just disconnect the battery, use a pressure bleeder and bleed normally. You will have to use a bit more fluid for the first time (~2x system capacity or ~1.5-2.0L), since early one new and old fluid are mixed. After first time, just bleed enough from the calipers as you change pads to insure that old fluid is pushed out and refreshed with new.

I use motiv bleeder as a pressure source only, take my time refilling the reservoir so it never drops below min. (will remove as much old fluid as possible, without going below min prior to first flush.

It is a bit of a slow process, requiring you to depressurize add more fluid, re-pressurize a few times, but it is by far the best way to prevent any air from ever getting into the system. The bleed screws are only cracked open with pressurized fluid in the system. I use Motul instead of SRF because it is cheaper and I have an electronic brake fluid moisture tester and have never seen any measurable increase in moisture over a season, so I could care less about wet boiling point.

P.S. If you try to do all these crazy things before/after a track day like GM's doc, you will go crazy. Just set up the car based on your street/track expected use and enjoy. For 99% of people doing one or two track day no prep would be just fine.


As to why you need to disconnect the brake fluid sensor, I'm guessing is to avoid a code from too low/too high fluid that will need to be cleared, but if anyone finds otherwise please post.

 

I also use a Motiv bleeder as a pressure source only the same method you describe. On my previous C7 and C6 usually 1 litre is all I needed for a flush. The capacity of those systems I recall was approximately half litre and wanted to confirm the C8 was the same. I am getting the dealer to do the flush as part of the PDI today and left them with 1 litre SRF and the feedback I got was the shop was concerned it would take more.
I plan on doing as suggested and leave the SRF brake fluid in the car, not remove the Z51 "track" ducts and leave my slightly less aggressive track alignment after track days. My only concern is trying to balance an alignment so I get the best tire wear without having to change it every time. Thinking of caster -2.5 front and -2.0 rear. typical year 10-15 track days.

 

Does the "GM cap" for the motiv that worked on my C5 and C7 work on the C8?

 

Alignment is my concern as well. I intend to drive the car a lot and road trip it and do 3-4 weekends a year at VIR. I was going to do the same as my C5 and C7 street cars with about -1.5 front and -1 rear, but I'm hearing that the car will destroy tires w/o camber and the NCM and others are recommending the full GM track alignment. I really don't want to run through a set of $1,700 tires every 5,000 miles.

 

I had my dealer do the track prep for me during PDI and they introduced air into the brake system. Now they cannot get rid of the code and GM technical support has not provided a solution. Anyone here experience this problem and know how to fix it?

My car was to be delivered on Monday but they spent all week trying to fix this problem. Still waiting for GM engineering to get back to the dealer with a solution (they must all be on vacation or something and don't call back). The dealer tech tried to do the bleed without disconnecting the battery or the GM procedure:" Disconnect brake fluid level sensor", and "Use Global Diagnostic System (GDS) to deactivate brake boost system". They introduced air into the system and after many flushes they think all the air is gone, and say the pedal feels firm but cannot clear the codes. I have my OnStar activated and I keep getting a warning that the antilock brakes have an immediate problem. I asked for this track prep to get me on the track ASAP and now it has been a week sitting at the dealer. I have not even sat in the car yet and have only seen it from a distance as they won't allow me in their shop. Any help is appreciated.

 

Use another dealer next time

 

Did anyone who actually do the brake flush take note on how much brake fluid the used?

 

A little less than 2 bottles of SRF.

 

Did anybody post this? This is from the 2020 Corvette Track Preparation guide:

PREPARE THE BRAKES BRAKE FLUID
Replace existing brake fluid with a qualified high-performance brake fluid from a sealed container. Brake fluid with a dry boiling point >590 F (310 C) is qualified. If high-performance brake fluid is used, replace it with GM-approved brake fluid before driving on public roads. If high-performance brake fluid is in the vehicle and the age of the brake fluid is over a month old or unknown, replace the brake fluid before track events and competitive driving. Do not use silicone or DOT-5 brake fluids.

Note: It is critical to disconnect the negative battery cable when any brake fluid flush procedures are performed. Flush the brake system – either manually bleeding or pressure bleeding is required. Vacuum bleeding is not recommended.

 

Castrol SRF annually and be done with it. Had dealer flush and it was simple with their computer. Charged me an hour labor.

 

 

I made a mistake at the start of the brake flush. I first disconnected the negative terminal but realized I needed to open the driver's door to allow my friend to pump the brakes. But forgot to disconnect again. Then at the start of bleeding, I heard the electric brake booster operating...clicks and electric noised. I realized my mistake, and disconnected the negative terminal and proceeded to bleed by my friend pumping the brake pedal.

Then after all the calipers were bleed with Castrol high temp brake fluid I took it on a test drive. Then the "ESC Disable" error message (electronic stability control) came on and it warned that speed limited to 62 mph. Crap. The brakes felt funny and I could hear the electronic boost system making clicking noises. I tried a few quick stops at low speed but that didn't help. Then while the car was running in park, I stood on the brake pedal very firmly for maybe 15 seconds while the electronic boost system clicked away then it finally it stop. I figured the electronic brake boost system either was broken now or needed to cycle a few times to get the boost system fully pressurized. And that worked!!!! No more ESC Disable light!!!

I also had a CEL. Using my wireless Kiwi dongle plugged into the OBDII port, I could see it was "U0401 Invalid data received from the ECM.OCM". I Googled that and it related to the fuel pump. I figured that was because I pulled the negative battery cable. I could not get it to "reset" using the software I had. But I didn't worry about that too much since the car ran fine and went to COTA to race with the Edge Addicts. On the first lap, the light went out, so everything after that went smoothly. Probably needed a few engine starts to go away.

 

Has anyone used their Motive bleeder to pressure bleed their C8 brakes yet? I'm about to order the Motive kit, but am a total novice to using it. My plan is to remove some fluid from the master cylinder, then top off with fresh fluid and use the Motive to pressure bleed each caliper until the fluid level is down to just above the 'minimum' line. Then fill and repeat until all four corners are bled. Anyone used this method successfully yet?

 

I haven't done it on a C8, but that is the procedure I have used on every vehicle I've had. If you do it exactly as you describe, and tighten the bleed screws without letting pressure drop, there is zero chance of introducing air in the system, and there is no way to mess it up. I would not go all the way down to min line (I'm just paranoid about it), just in case the electric booster kicks in or you inadvertently leave the bleed screw open too long.

I've been doing this forever. Every time I changed brake pads I repeat the above procedure to get old fluid out of the calipers. This way I always have fresh fluid in the system.

Your procedure is still the best way, IMHO. Good luck.


P.S. I assume you have a clear tube and bottle to catch the bled fluid. Good way to detect air, impurities, etc. You can also buy a fluid moisture tester and keep track of moisture content on your fluid. (hint: you will never see any significant moisture on a newer, well maintained car)