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C8 Z51 Brake System Guide

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Old Feb 4, 2024 | 11:26 PM
  #21  
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Originally Posted by David Snell
new front cross drilled slotted rotors.
No drilled rotors. Ever.

They do nothing to help and are generally an indication of a shitty base rotor underneath it.

It's like playing Stairway to Heaven at the guitar store.
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Old Feb 6, 2024 | 11:37 AM
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Originally Posted by mikegr
that is odd, as in bleed from the fluid resovoir without using any of the bleed screws on the caliper? I wouldn’t even know how that could possibly work if that’s what you mean.
Pretty sure what they are talking about is the "official" GM method for replacing fluid in the C8 which uses a specific GM tool that connects to the reservoir cap and pressure bleeds the system.
Btw, it was commented previously WHY would you want to replace your fluid vs just bleed the brakes? There are many reasons:
1) For DD use, DOT4 is very sensitive to moisture and once water gets into the fluid, the performance characteristics are greatly compromised. Fluid boils at much lower temps, etc.
2) For track use, GM recommends changing the RBF after EACH EVENT. I was using Motul 660 RBF and didn't have the fluid in my brakes for even 12 months before it failed on me. It failed while on the track and going into a heavy braking zone before a turn. "BRAKE SYSTEM FAILURE". Something you don't want to see on the DIC at that particular time. I replaced the fluid with Castrol SRF because it appears to last longer, but I will pressure bleed it every year regardless.
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Old Feb 6, 2024 | 06:14 PM
  #23  
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Originally Posted by dohabandit
Pretty sure what they are talking about is the "official" GM method for replacing fluid in the C8 which uses a specific GM tool that connects to the reservoir cap and pressure bleeds the system.
Btw, it was commented previously WHY would you want to replace your fluid vs just bleed the brakes? There are many reasons:
1) For DD use, DOT4 is very sensitive to moisture and once water gets into the fluid, the performance characteristics are greatly compromised. Fluid boils at much lower temps, etc.
2) For track use, GM recommends changing the RBF after EACH EVENT. I was using Motul 660 RBF and didn't have the fluid in my brakes for even 12 months before it failed on me. It failed while on the track and going into a heavy braking zone before a turn. "BRAKE SYSTEM FAILURE". Something you don't want to see on the DIC at that particular time. I replaced the fluid with Castrol SRF because it appears to last longer, but I will pressure bleed it every year regardless.
I have used the Motul stuff in many other cars and seemed to work well. Have only used SRF in the C8 and I do generally flush the system at least twice per year. Has been good so far. If as you mention the dealer was referring to the official GM bleed method and doing a pressure bleed, that is the same process I have used on the car and had no issues. All other cars I had vacuum bled.
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Old Feb 7, 2024 | 12:08 AM
  #24  
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Read the chart.


This chart is from Amsoil


DOT 3 - Camry
DOT 4 - Truck/better car if you think 25 degrees is the difference.
DOT 5 - Useless - it does not absorb water.
DOT 5.1 - a stupid name - it's a better DOT 4

None of these are track fluids.

Track fluid starts at around 600 wet/400 dry

Castrol is better - because wet is what really matters and it's up around 500. Every racer ever knows it. It's better. And yeah $75 but you get a full liter.

A C8 Z51 is going to roast the front brakes at any pace past medium. That includes the fluid. Please explain why you would spend all that $$ to go to the track and ignore one of the things that keeps you from going off track.

It's a simple hydraulic system with a bunch of sensors attached and an inline auxillary pump. gravity provides 14.7 psi - works fine to bleed and then finish with the 2 man method.

Thanks for listening to my Ted Talk. I saw a few too many posts in here to not reply.



Last edited by KNSBrakes; Feb 7, 2024 at 11:09 AM.
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Old Feb 7, 2024 | 01:14 AM
  #25  
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Saw some video online, where you need the GM scan tool tool to do this? Thata bs right?

Also, what is the proper bleeding sides?
Rear passenger > front driver > rear driver > front passenger

Or

Rear driver > front passenger > rear passenger > front driver?
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Old Feb 7, 2024 | 10:28 AM
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Originally Posted by KNSBrakes

Castrol is better - because wet is what really matters and it's up around 500. Every racer ever knows it. It's better. And yeah $75 but you get a full liter.

.
Ken,, a couple of dumb questions if I might. Besides being a bit more expensive, are there any downsides to running a fluid like the Castrol in a mostly street car? Also, they talk about compatibility with DOT 3 & 4 but mention 'silicon ester technology' in their publications. That implies a DOT 5 fluid to me but what do I know. Would this be considered a silicon DOT5 type fluid?

'Castrol SRF is the ultimate racing brake fluid. Its unique silicon ester technology absorbs less water than conventional glycol ether fluids and prevents the fluid's high-temperature performance from deteriorating.'
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Old Feb 7, 2024 | 10:45 AM
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Originally Posted by gtpvette
Ken,, a couple of dumb questions if I might. Besides being a bit more expensive, are there any downsides to running a fluid like the Castrol in a mostly street car? Also, they talk about compatibility with DOT 3 & 4 but mention 'silicon ester technology' in their publications. That implies a DOT 5 fluid to me but what do I know. Would this be considered a silicon DOT5 type fluid?

'Castrol SRF is the ultimate racing brake fluid. Its unique silicon ester technology absorbs less water than conventional glycol ether fluids and prevents the fluid's high-temperature performance from deteriorating.'
No dumb questions.

And I have the same question as you on the Castrol. Not sure exactly what it is on that silicon reference - I'm going to dig a bit and see if I can find out. But they are the secret sauce for sure. There was a shortage a few years back and racers were flipping the f%&* out.

I think you can certainly run it in a street car - are you tracking once in a while?

Ken
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Old Feb 7, 2024 | 11:22 AM
  #28  
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Originally Posted by KNSBrakes
No dumb questions.

And I have the same question as you on the Castrol. Not sure exactly what it is on that silicon reference - I'm going to dig a bit and see if I can find out. But they are the secret sauce for sure. There was a shortage a few years back and racers were flipping the f%&* out.

I think you can certainly run it in a street car - are you tracking once in a while?

Ken
I would like to do some track time at some point. That said, I have no delusions regarding my speed or ability to late brake LOL, so I don't think I'd be too hard on the brakes. When I swap in the new brakes, I'll be replacing most of the fluid so would like to use the good stuff so to speak.
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Old Feb 7, 2024 | 11:37 AM
  #29  
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Originally Posted by gtpvette
I would like to do some track time at some point. That said, I have no delusions regarding my speed or ability to late brake LOL, so I don't think I'd be too hard on the brakes. When I swap in the new brakes, I'll be replacing most of the fluid so would like to use the good stuff so to speak.
A C8 Z51 in the beginner groups.

OEM pads if pretty new are fine. Dust haters take them off all the time - $150 is the going rate.

Any good track fluid is fine at that level.

If you have not done a track day before you should schedule it right now. Imagine flooring the gas and NOT looking around for cops.
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Old Feb 7, 2024 | 12:09 PM
  #30  
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Originally Posted by MrPayDay
Saw some video online, where you need the GM scan tool tool to do this? Thata bs right?

Also, what is the proper bleeding sides?
Rear passenger > front driver > rear driver > front passenger

Or

Rear driver > front passenger > rear passenger > front driver?
The GM tech manual actually states that you need to run a procedure using their scan tool. I think this is to disable the brake booster so you can keep the battery connected.
They also state you should remove the brake fluid LEVEL sensor before working on brakes.

Since I don't have their fancy scan tool, for sure the battery must be disconnected because there is a chance the system will engage and remove (or at least extremely flatten) fingers of whoever is doing the work.
Since I disconnected the battery, I didn't bother to remove the fluid level sensor. Also, I am really puzzled why they talk about cycling the parking brake on/off. The EPB is electronic, uses a friggen motor, it's not hydraulic. Is it possible the GM notes I have are just a crappy COPY/PASTE from their general notes on brake fluid changes???

I think the GM service notes state to use a 30+ PSI pressure bleed (30-45 PSI actually). Anyway, I am not sure the reason for such high pressure during fluid replacement, so I kept it around 25PSI with no issues.
I did perform the brake pad squeeze pattern using some channel locks. There is a specific pattern to follow that helps to get the old fluid cycled out of the caliper pistons.

I have a word doc with the procedure steps, DM if you want it. I will try to paste it here:
2020 Chevrolet Corvette | Corvette Service Manual 13097125 | Brakes | Hydraulic Brakes | Repair Instructions | Document ID: 5417357

Hydraulic Brake System Bleeding (J55)
Special Tools
  • CH-29532-A Pressure Brake Bleeder
  • CH-44894-A Brake Bleeder Adapter
For equivalent regional tools. Special Tools

Warning: Brake Dust Warning

Warning: Brake Fluid Irritant Warning.

Caution: Brake Fluid Effects on Paint and Electrical Components Caution.

Caution: Only use products that comply with GM specifications and check manufacturer information respectively. We recommend the use of GM genuine products. Instructions must be followed at all times. The use of any type of fluid other than the recommended type of brake fluid, may cause contamination which could result in damage to the internal rubber seals and/or rubber linings of hydraulic brake system components.

Note: If the system is opened at the brake master cylinder, a full hydraulic brake system bleed is necessary.
Bleeding a Single Hydraulic Brake Circuit Note: The pressure bleeding equipment must be the diaphragm type. The rubber diaphragm between the air supply and the brake fluid prevents air, moisture, oil, and other contaminants from entering the hydraulic system.

Note: The brake reservoir may have residual pressure after the bleeding operation is complete. Wrap a clean shop towel around the bleeder adapter and all hose connections before disconnecting the pressure bleeding equipment to prevent brake fluid from contacting and damaging vehicle components and painted surfaces

Note: DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

  1. Disconnect brake fluid level sensor
  2. Use Global Diagnostic System (GDS) to deactivate brake boost system.
  3. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
  4. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
  5. Fill the brake master cylinder reservoir with GM approved brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Brake Master Cylinder Reservoir Filling
  6. Check the brake fluid level in the CH-29532-A Pressure Brake Bleeder. Add GM approved brake fluid from a clean, sealed brake fluid container as necessary to bring the level to approximately the half-full point. Adhesives, Fluids, Lubricants, and Sealers
  7. Install the CH-44894-A Brake Bleeder Adapter to the brake master cylinder reservoir.
  8. Connect the CH-29532-A Pressure Brake Bleeder, to the CH-44894-A Brake Bleeder Adapter.
  9. Charge the CH-29532-A Pressure Brake Bleeder, air tank to 207 - 310 kPa (30 - 45 psi).
  10. Open the CH-29532-A Pressure Brake Bleeder, fluid tank valve to allow pressurized brake fluid to enter the brake system.
  11. Wait approximately 30 seconds, then inspect the entire hydraulic brake system in order to ensure that there are no existing external brake fluid leaks. Any brake fluid leaks identified require repair prior to completing this procedure. Brake System External Leak Inspection
  12. Install a proper box-end wrench onto the wheel hydraulic circuit bleeder valve which has been serviced.
  13. Install a transparent hose over the end of the bleeder valve.
  14. Submerge the open end of the transparent hose into a transparent container partially filled with GM approved brake fluid from a clean, sealed brake fluid container. Adhesives, Fluids, Lubricants, and Sealers
  15. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
  16. Allow fluid to flow until air bubbles stop flowing from the bleeder.
  17. Cycle the park brake ON and OFF after opening the bleeder valve on the rear calipers.
  18. After all air has been purged from the hydraulic circuit, tighten the bleeder valve to the necessary torque specification and install the dust cap.
  19. Close the CH-29532-A Pressure Brake Bleeder, fluid tank valve, then disconnect the CH-29532-A Pressure Brake Bleeder, from the CH-44894-A Brake Bleeder Adapter.
  20. Remove the CH-44894-A Brake Bleeder Adapter from the brake master cylinder reservoir.
  21. Fill the brake master cylinder reservoir to the maximum-fill level with GM approved brake fluid from a clean, sealed brake fluid container. Adhesives, Fluids, Lubricants, and Sealers
  22. Inspect the brake system for external leaks. Brake System External Leak Inspection
  23. Run the GDS - Brake Hydraulic Test, if it fails, perform the Bleeding the Complete Brake Hydraulic System procedure.
  24. Connect the brake fluid level sensor
  25. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
  26. Inspect the brake system for external leaks. Brake System External Leak Inspection
  27. If the brake system warning lamp remains illuminated, go to Diagnostic Starting Point - Vehicle.
Bleeding Complete Brake Hydraulic SystemNote: The pressure bleeding equipment must be the diaphragm type. The rubber diaphragm between the air supply and the brake fluid prevents air, moisture, oil, and other contaminants from entering the hydraulic system.

Note: Squeeze rapidly, faster pad/piston retraction guarantees high fluid flow to release air.

Note: DO NOT allow the vehicle to be driven until it is diagnosed and repaired.

  1. Disconnect brake fluid level sensor
  2. Use Global Diagnostic System (GDS) to deactivate brake boost system.
  3. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
  4. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.
  5. Fill the brake master cylinder reservoir with GM approved brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Brake Master Cylinder Reservoir Filling
  6. Check the brake fluid level in the CH-29532-A Pressure Brake Bleeder. Add GM approved brake fluid from a clean, sealed brake fluid container as necessary to bring the level to approximately the half-full point. Adhesives, Fluids, Lubricants, and Sealers
  7. Install the CH-44894-A Brake Bleeder Adapter to the brake master cylinder reservoir.
  8. Connect the CH-29532-A Pressure Brake Bleeder, to the CH-44894-A Brake Bleeder Adapter.
  9. Charge the CH-29532-A Pressure Brake Bleeder, air tank to 207 - 310 kPa (30 - 45 psi).
  10. Open the CH-29532-A Pressure Brake Bleeder, fluid tank valve to allow pressurized brake fluid to enter the brake system.
  11. Wait approximately 30 seconds, then inspect the entire hydraulic brake system in order to ensure that there are no existing external brake fluid leaks. Any brake fluid leaks identified require repair prior to completing this procedure. Brake System External Leak Inspection
  12. Install a proper box-end wrench onto the RIGHT FRONT wheel hydraulic circuit bleeder valve.
  13. Install a transparent hose over the end of the bleeder valve.
  14. Submerge the open end of the transparent hose into a transparent, graduated container partially filled with GM approved brake fluid from a clean, sealed brake fluid container. Note amount of fluid in the container. Adhesives, Fluids, Lubricants, and Sealers
  15. Open bleeder, allow fluid to flow for 10 seconds, close bleeder and repeat the step two more times before moving on.
  16. Reopen bleeder, use channel locks to quickly squeeze pad to caliper in locations by each piston beginning with Sequence A, then repeating with Sequence B:
    1. Sequence A: Beginning with the pad section furthest from the bleeder and ending with the pad section nearest to the bleeder:
      1. Outboard leading piston
      2. Inboard leading piston
      3. Outboard trailing piston
      4. Inboard trailing piston
    2. Sequence B: Beginning with the pad section nearest to the bleeder and ending with the pad section furthest from the bleeder:
      1. Inboard trailing piston
      2. Inboard leading piston
      3. Outboard trailing piston
      4. Outboard leading piston
  17. Use a mallet to tap 3 times behind each piston and 3 times tangentially on the top and bottom of caliper.
  18. Close bleeder and wait 5 seconds to allow pressure to rebuild and pistons/pads to spread back out to rotor.
  19. Repeat steps 3-5 four more times.
  20. Close RF bleeder and repeat entire process for LF caliper.
  21. Install an appropriate box-end wrench onto the LEFT REAR wheel hydraulic circuit bleeder valve.
  22. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
  23. Allow fluid to flow until air bubbles stop flowing from the bleeder.
  24. After all air has been purged from the hydraulic circuit, close the bleeder valve.
  25. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve, then repeat steps 23-25.
  26. After all air has been purged from the hydraulic circuit, tighten the bleeder valve to the necessary torque specification and install the dust cap.
  1.  
  2. Close the CH-29532-A Pressure Brake Bleeder, fluid tank valve, then disconnect the CH-29532-A Pressure Brake Bleeder, from the CH-44894-A Brake Bleeder Adapter.
  3. Remove the CH-44894-A Brake Bleeder Adapter from the brake master cylinder reservoir.
  4. Fill the brake master cylinder reservoir to the maximum-fill level with GM approved brake fluid from a clean, sealed brake fluid container. Adhesives, Fluids, Lubricants, and Sealers
  5. Inspect the brake system for external leaks. Brake System External Leak Inspection
  6. Run the GDS — Brake Hydraulic Test, if it fails.  Antilock Brake System Automated Bleed
  7. Connect the brake fluid level sensor
  8. Turn the ignition ON, with the engine OFF. Check to see if the brake system warning lamp remains illuminated.
  9. If the brake system warning lamp remains illuminated, go to Diagnostic Starting Point - Vehicle.



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Old Feb 7, 2024 | 12:28 PM
  #31  
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Originally Posted by KNSBrakes
A C8 Z51 in the beginner groups.

OEM pads if pretty new are fine. Dust haters take them off all the time - $150 is the going rate.

Any good track fluid is fine at that level.

If you have not done a track day before you should schedule it right now. Imagine flooring the gas and NOT looking around for cops.
GM states you MUST install racing brake fluid, and swap it back to daily driving fluid after each track event. Z51 come with the brembo pads which are great for beginner track use, but the car comes with standard DOT4 fluid that is guaranteed to fail on the track.

I wanted a "paper trail" for warranty purposes, so I originally paid the dealer to install Motul RBF. My brakes then FAILED on the track in the most extreme sphincter clamping way you can imagine. I was at WOT heading into a wide banked turn and went to full brakes before getting into balance, suddenly brake system just shut down. "BRAKE SYSTEM FAILURE" on the DIC.
Fortunately I managed to reduce speed enough and had a good line, but ended getting a lot closer to the wall than I have ever been. There was no sign of reduced braking performance or overheating alert or anything. Once the brake system failed, the pedal became very stiff. Not mushy like it had bubbles in the fluid, it was stiff and as hard as you pressed there were just NO BRAKES.
I suspect the GM tech didn't actually install the Motul. I saw signs also that there was damage to my brake fluid reservoir, nicks on the top surface of the filler neck that prevented MY pressure bleeder from sealing properly. I also have big nicks or dings on the sides of the reservoir like some ******* idiot tried to clamp a universal cap on it. I ended up having to get a special cap actually made for a Tesla, and it uses an internal o-ring to seal up the filler neck. Spraying DOT4 out a pressure is not good for your paint! Good thing I was concerned about pressure bleeding and had covered the work area with shipping blankets, and also wrapped a bunch of towels around the cap and reservoir. Once I opened the pressure valve, RBF was spraying out like mad using the cap that is supposed to work for GM/C8.

Brakes are probably the single most important thing to have working properly on the track. Paper trail be damned, I don't trust the "technicians" at the dealer to touch my brakes anymore. Especially when my life is on the line. They also used an impact on my lugs and probably put 300lbs of torque on them.
I installed Castrol SRF and have tracked several times since then with no brake issues. I will replace the Castrol fluid once a year.
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Old Feb 7, 2024 | 12:58 PM
  #32  
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Just to be clear,,, my car isn't a Z51 just a base, no option car. I do have all the parts for the Z06 brakes though, just need to install them. Based on Kens comments, I'll try the Motul for fluid and save a few bucks. For pads, I have CarboTech 1521 street pads I got from KNS but will be looking for a set of track pads in the near future. I'll make a point to watch the parts section if a set of OEM's come up though,, a good thought thanks.

@dohabandit A couple questions for you. Did you figure out exactly what happened to your brakes?? Fluid boil? That whole scenario is a bit unsettling. You also mention 'no sign of reduced braking performance or overheating alert', does the C8 normally warn about these things?
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Old Feb 7, 2024 | 10:56 PM
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Not 100% sure. If the fluid boiled, I would assume the pedal would get spongy with no braking effect, but the pedal wasn't soft, it was quite firm. Is this an effect of the brake booster?

My assumption though is my fluid boiled and this could be from two causes as far as I am concerned:
1) The Motul RBF had expired in my car and had absorbed too much water. The boiling point of Motul when wet is pretty shitty.
2) The Motul RBF that I paid to have installed was never installed and I was running on the track using stock fluid. The failure to get a pressure seal on my reservoir makes me think the tech SCREWED UP. I know for a fact the damage wasn't caused by me. Maybe the tech thought all we were doing was BLEEDING and not swapping fluid entirely??? I did get one extra bottle of Motul back from them after the work was done and I questioned that because the number of bottles I got didn't leave much room for extra and the Motul bottles are pretty small compared to Castrol SRF.
3) I don't think there was air in my system, but there is a procedure you are supposed to run to cycle the ABS valves. Supposedly the ABS valves hold onto air somehow and you are supposed to cycle them using a scan tool WHILE pressure bleeding. Maybe this is an issue if you have air in the lines already and aren't just pushing new fluid through? I have been searching for a safe dye to use btw. I have seen some recommended, but nothing I have heard approved for use in C8. A dye would sure make swapping fluid out a lot easier, and less wasteful.

If you have a non-Z51 car, I am not sure they use the same pads as the Z51 version.
The Z51 has larger diameter rotors and larger calipers. Maybe the pads are interchangeable? Not sure, but I wouldn't assume that pulled Z51 track pads would work on a non-Z51 caliper.
The brake code for non-Z51 is JL9 and the Z51 are J55 brakes. I thought the carbotech 1521 compound made for C8 were Z51 / J55 only pads?

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Old Feb 8, 2024 | 11:16 AM
  #34  
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Originally Posted by dohabandit
The brake code for non-Z51 is JL9 and the Z51 are J55 brakes. I thought the carbotech 1521 compound made for C8 were Z51 / J55 only pads?
I'm moving to Z06 J56 brakes. I need track pads for these, have 1521's for the street.
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Old Feb 8, 2024 | 11:15 PM
  #35  
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Originally Posted by dohabandit
GM states you MUST install racing brake fluid, and swap it back to daily driving fluid after each track event. Z51 come with the brembo pads which are great for beginner track use, but the car comes with standard DOT4 fluid that is guaranteed to fail on the track.

I wanted a "paper trail" for warranty purposes, so I originally paid the dealer to install Motul RBF. My brakes then FAILED on the track in the most extreme sphincter clamping way you can imagine. I was at WOT heading into a wide banked turn and went to full brakes before getting into balance, suddenly brake system just shut down. "BRAKE SYSTEM FAILURE" on the DIC.
Fortunately I managed to reduce speed enough and had a good line, but ended getting a lot closer to the wall than I have ever been. There was no sign of reduced braking performance or overheating alert or anything. Once the brake system failed, the pedal became very stiff. Not mushy like it had bubbles in the fluid, it was stiff and as hard as you pressed there were just NO BRAKES.
I suspect the GM tech didn't actually install the Motul. I saw signs also that there was damage to my brake fluid reservoir, nicks on the top surface of the filler neck that prevented MY pressure bleeder from sealing properly. I also have big nicks or dings on the sides of the reservoir like some ******* idiot tried to clamp a universal cap on it. I ended up having to get a special cap actually made for a Tesla, and it uses an internal o-ring to seal up the filler neck. Spraying DOT4 out a pressure is not good for your paint! Good thing I was concerned about pressure bleeding and had covered the work area with shipping blankets, and also wrapped a bunch of towels around the cap and reservoir. Once I opened the pressure valve, RBF was spraying out like mad using the cap that is supposed to work for GM/C8.

Brakes are probably the single most important thing to have working properly on the track. Paper trail be damned, I don't trust the "technicians" at the dealer to touch my brakes anymore. Especially when my life is on the line. They also used an impact on my lugs and probably put 300lbs of torque on them.
I installed Castrol SRF and have tracked several times since then with no brake issues. I will replace the Castrol fluid once a year.
That's a terrible experience and frankly that dealer should be outed and held accountable.

And it's why I think pressure bleeders are not the answer.

The brakes bleed fine with gravity and/or a few 2 man pedal pumps. At some point I'd like to flush the ABS - that requires the computer but I still don't use a pressure bleeder. Just keep a continuous column of fluid above the MC pistons and air cannot get in the system.

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Old Feb 10, 2024 | 07:46 AM
  #36  
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gm track got bs lawyer verbiage imho. it says lower the car and return to stock height. also say change tires every 2 tank of gas or approx 100 miles. I run the ap competition brake system in feont and do full bleed every 6 months without any issues with motul 660 or srf.

i have seen camaro ss 1le boil its brake after full motul 660 done at track. i was the one helping him. also friend boiled srf on zl1 and switched to full ap system. I switch just like you say, don't want brake failure on track.

Originally Posted by dohabandit
Pretty sure what they are talking about is the "official" GM method for replacing fluid in the C8 which uses a specific GM tool that connects to the reservoir cap and pressure bleeds the system.
Btw, it was commented previously WHY would you want to replace your fluid vs just bleed the brakes? There are many reasons:
1) For DD use, DOT4 is very sensitive to moisture and once water gets into the fluid, the performance characteristics are greatly compromised. Fluid boils at much lower temps, etc.
2) For track use, GM recommends changing the RBF after EACH EVENT. I was using Motul 660 RBF and didn't have the fluid in my brakes for even 12 months before it failed on me. It failed while on the track and going into a heavy braking zone before a turn. "BRAKE SYSTEM FAILURE". Something you don't want to see on the DIC at that particular time. I replaced the fluid with Castrol SRF because it appears to last longer, but I will pressure bleed it every year regardless.
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Old Feb 10, 2024 | 09:25 AM
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Originally Posted by cars
gm track got bs lawyer verbiage imho. it says lower the car and return to stock height. also say change tires every 2 tank of gas or approx 100 miles. I run the ap competition brake system in feont and do full bleed every 6 months without any issues with motul 660 or srf.

i have seen camaro ss 1le boil its brake after full motul 660 done at track. i was the one helping him. also friend boiled srf on zl1 and switched to full ap system. I switch just like you say, don't want brake failure on track.
I was pushing the C8 really hard at the time brakes failed. Newbs will brake too soon and hold the brakes too long which actually heats them up more.
I was going WOT and then FULL brakes at the last possible moment getting into balance. My best top speed was also not far (-5MPH) from the top speed on that track.

When you installed new Motul 660 at the track, did you compress the calipers using the X pattern or just open the bleeder and let it run into a catch bottle? It seems to me that the most important area to remove all the old fluid and also the area most easily exposed to water is within the caliper itself. Since brakefluid isn't circulating, maybe some old fluid remained and then boiled?

I agree about the "bs lawyer verbiage". You see the same in extended warranty plans. Typically they will say you need to follow ALL dealer recommended service practices including replacing the CABIN AIR FILTER. So if your DCT fails and the cabin air filter wasn't replaced on time they will deny your claim! Not saying GM does this, but one of the top aftermarket service contract "PLATINUM" plans does just that and the BBB page is full of horror stories where a failed timing chain was denied due to a cabin air filter that was dirty.
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Old Feb 10, 2024 | 09:46 AM
  #38  
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Originally Posted by KNSBrakes
That's a terrible experience and frankly that dealer should be outed and held accountable.

And it's why I think pressure bleeders are not the answer.

The brakes bleed fine with gravity and/or a few 2 man pedal pumps. At some point I'd like to flush the ABS - that requires the computer but I still don't use a pressure bleeder. Just keep a continuous column of fluid above the MC pistons and air cannot get in the system.
I am not going to out the dealer because I don't know for sure they didn't actually install the Motul 660, and I also don't know for sure that the reservoir filler neck wasn't aready damaged from BGA. The scratches are small, but enough to prevent the standard cap from sealing and pressure bleeding.

Here's a pic, and also a pic of the tesla cap that I got that works (and just barely fits).



The damage to top of filler neck made a gouge and displaced some plastic (arrows). I am thinking to carefully cut away the uplifted plastic with a razor, or maybe just heat up a blade and try to smooth it out again next time I try pressure bleeding. There is still a channel there though for air/fluid to escape.
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Old Feb 10, 2024 | 08:48 PM
  #39  
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Originally Posted by KNSBrakes
That's a terrible experience and frankly that dealer should be outed and held accountable.

And it's why I think pressure bleeders are not the answer.

The brakes bleed fine with gravity and/or a few 2 man pedal pumps. At some point I'd like to flush the ABS - that requires the computer but I still don't use a pressure bleeder. Just keep a continuous column of fluid above the MC pistons and air cannot get in the system.
Ken,, would love to hear in painful detail your best practices on bleeding brakes. Please. I have new calipers and lines that need to be installed and remain confused between gravity, pressure or the old tried and true two-man method. Note that I only have my wife for the two-person method. I love her but don't want to go there if possible LOL. Any insight would be greatly appreciated.
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Old Feb 11, 2024 | 10:09 AM
  #40  
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Here's some extra info about what I thought "should" happen with a brake fluid boil.
I should have seen stages with warnings that brakes were overheating with two stages, etc. My failure went from brakes working fine, full braking with no fade feeling, and then SUDDENLY no brakes, stiff pedal and a "BRAKE SYSTEM FAILURE" message on the DIC.

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