High-speed Temporary Ineffective Braking - CorvetteForum - Chevrolet Corvette Forum Discussion

Notices
C6 Tech/Performance LS2, LS3, LS7, LS9 Corvette Technical Info, Internal Engine, External Engine, Tech Topics, Basic Tech, Maintenance, How to Remove & Replace
Sponsored by:
Sponsored by:

High-speed Temporary Ineffective Braking

Reply

 
 
 
Old 06-13-2018, 10:22 AM
  #1  
Lotsokids
Junior Member
Thread Starter
 
Lotsokids's Avatar
 
Member Since: Dec 2017
Location: Moore Oklahoma
Posts: 23
Thanked 2 Times in 2 Posts
Default High-speed Temporary Ineffective Braking

Yesterday I experienced something rather scary. I'll admit, I was aggressive and stupid. "Messed with" another vehicle, and down-shifted to third at about 65 MPH, and accelerated to the redline, then I braked hard as there were other cars on the highway. My car was not stopping very quickly, and I stood on the brakes. It felt like someone greased my rotors. It was VERY slow braking. The situation diffused, but was very unnerving. I attempted to brake hard again a few minutes later, and it felt fine. Pads and rotors appear fine. Driving to work this morning at about 50 MPH, I stood on the brakes, and it stopped immediately with slight chirping of the tires.
This is a VERY big problem if you cannot brake at high speed. Not sure what's going on.
Any ideas?
Lotsokids is offline  
Reply With Quote
Old 06-13-2018, 10:42 AM
  #2  
RicK T
CF Senior Member
 
RicK T's Avatar
 
Member Since: Sep 2005
Location: Las Vegas, Nevada
Posts: 20,092
Thanked 436 Times in 360 Posts
Default

Just spitballin' here, but if I understand your description, you were WOT, at redline, in 3rd gear and immediately braked hard. I'm not sure it's possible but "maybe" you inadvertently found a fraction of a second when there was insufficient vacuum for the brake booster. It might help if you can clarify exactly the circumstances at the time of braking. Did you get off the throttle completely then to the brakes or was there any overlap time with WOT and braking?

I will be interested to see what the group has to say about this. Be patient for responses the next couple days.
RicK T is offline  
Reply With Quote
Old 06-13-2018, 10:48 AM
  #3  
Lotsokids
Junior Member
Thread Starter
 
Lotsokids's Avatar
 
Member Since: Dec 2017
Location: Moore Oklahoma
Posts: 23
Thanked 2 Times in 2 Posts
Default

Originally Posted by RicK T View Post
Just spitballin' here, but if I understand your description, you were WOT, at redline, in 3rd gear and immediately braked hard. I'm not sure it's possible but "maybe" you inadvertently found a fraction of a second when there was insufficient vacuum for the brake booster. It might help if you can clarify exactly the circumstances at the time of braking. Did you get off the throttle completely then to the brakes or was there any overlap time with WOT and braking?

I will be interested to see what the group has to say about this. Be patient for responses the next couple days.
Pretty rapidly switched from WOT to hard braking.
Another note is that I don't think I pumped the brakes - just stood on them. Felt like I was trying to stop a dump truck.

Last edited by Lotsokids; 06-13-2018 at 10:51 AM.
Lotsokids is offline  
Reply With Quote
Old 06-13-2018, 12:09 PM
  #4  
[email protected]'dAutosport.com
Supporting Vendor
 
Adam@Amp'dAutosport.com's Avatar
 
Member Since: Oct 2002
Location: Cleveland OH
Posts: 27,379
Thanked 178 Times in 166 Posts
St. Jude Donor '11,'13
Default

What pad are you using? You may have faded them..
__________________
Adam Adelstein
Amp’D Autosport.com
Internet's largest retailer of Carbotech Performance Brake Pads.
PH:216-780-8825.
Email: [email protected]
Web Site & Direct ordering http://ampdautosport.com/
All major CC and Pay Pal accepted.
Check out Promo code:z28
Adam@Amp'dAutosport.com is online now  
Reply With Quote
Old 06-13-2018, 02:58 PM
  #5  
Lotsokids
Junior Member
Thread Starter
 
Lotsokids's Avatar
 
Member Since: Dec 2017
Location: Moore Oklahoma
Posts: 23
Thanked 2 Times in 2 Posts
Default

Originally Posted by [email protected]'dAutosport.com View Post
What pad are you using? You may have faded them..
I'm not sure. They were installed when I bought the car.
Is that an indication when you can practically lock up the wheels (as much as antilock will allow) at 50 MPH, but can't stop at 100+?
I do know rotors can get "glazed" from heat. I don't know if that's my issue, either.
Lotsokids is offline  
Reply With Quote
Old 06-13-2018, 04:23 PM
  #6  
[email protected]'dAutosport.com
Supporting Vendor
 
Adam@Amp'dAutosport.com's Avatar
 
Member Since: Oct 2002
Location: Cleveland OH
Posts: 27,379
Thanked 178 Times in 166 Posts
St. Jude Donor '11,'13
Default

Originally Posted by Lotsokids View Post
I'm not sure. They were installed when I bought the car.
Is that an indication when you can practically lock up the wheels (as much as antilock will allow) at 50 MPH, but can't stop at 100+?
I do know rotors can get "glazed" from heat. I don't know if that's my issue, either.

Main causes of brake fade


Brake fade is a reduction (or total absence) of the stopping power of your brake system that occurs as a result of overheated brake pads. Simply put, it's when you push on pedal and the vehicle doesn't slow like you planned. No amount of additional foot pressure can make you stop quicker. While it is most commonly associated with race cars and heavy trucks that put high demands on the braking system, as you'll read below it can occur on any vehicle that uses friction based deceleration.

It's a particularly significant issue compared to other system failures because once the driver has hit the brakes - they've already committed to the event and there isn't much time to correct when it goes awry. Brake fade manifests itself with a very firm yet ineffective brake pedal. If your braking issue is not accompanied by a firm or hard brake pedal - you don't have brake fade. You will need to look deeper for your issue.

So how do you know if you have brake fade?
◾Your brake pedal is firm (soft pedal is a different condition)
◾Your brakes are not effective.
◾Pumping the brake pedal does not help
◾Once the system has cooled, performance usually returns (although permanently at a reduced effective level)
__________________
Adam Adelstein
Amp’D Autosport.com
Internet's largest retailer of Carbotech Performance Brake Pads.
PH:216-780-8825.
Email: [email protected]
Web Site & Direct ordering http://ampdautosport.com/
All major CC and Pay Pal accepted.
Check out Promo code:z28
Adam@Amp'dAutosport.com is online now  
Reply With Quote
The Following User Says Thank You to [email protected]'dAutosport.com For This Useful Post:
Lotsokids (06-14-2018)
Old 06-13-2018, 04:54 PM
  #7  
ls404fd
CF Member
 
Member Since: Oct 2011
Posts: 86
Thanks: 0
Thanked 1 Time in 1 Post
Default

Was there ABS activation with a pulsing pedal, or was it just a hard pedal? Was there any noise when you hit the brake?

When the situation diffused itself, do you mean the brakes started working? What was different?
ls404fd is offline  
Reply With Quote
Old 06-13-2018, 06:18 PM
  #8  
RobJoy
CF Senior Member
 
RobJoy's Avatar
 
Member Since: Nov 2013
Location: western NC
Posts: 281
Thanked 18 Times in 17 Posts
Default

Originally Posted by Lotsokids View Post
Yesterday I experienced something rather scary. I'll admit, I was aggressive and stupid. "Messed with" another vehicle, and down-shifted to third at about 65 MPH, and accelerated to the redline, then I braked hard as there were other cars on the highway. My car was not stopping very quickly, and I stood on the brakes. It felt like someone greased my rotors. It was VERY slow braking. The situation diffused, but was very unnerving. I attempted to brake hard again a few minutes later, and it felt fine. Pads and rotors appear fine. Driving to work this morning at about 50 MPH, I stood on the brakes, and it stopped immediately with slight chirping of the tires.
This is a VERY big problem if you cannot brake at high speed. Not sure what's going on.
Any ideas?
Sound like the brake booster check valve may not be working. Under several seconds of hard acceleration and intake manifold vacuum dropping, the vacuum in the booster could have been equalized to atmospheric pressure, or close enough, to affect the booster's assistance if the one-way check valve is not staying closed.
RobJoy is offline  
Reply With Quote
The Following User Says Thank You to RobJoy For This Useful Post:
Lotsokids (06-14-2018)
Old 06-14-2018, 07:48 AM
  #9  
Lotsokids
Junior Member
Thread Starter
 
Lotsokids's Avatar
 
Member Since: Dec 2017
Location: Moore Oklahoma
Posts: 23
Thanked 2 Times in 2 Posts
Default

Originally Posted by ls404fd View Post
Was there ABS activation with a pulsing pedal, or was it just a hard pedal? Was there any noise when you hit the brake?

When the situation diffused itself, do you mean the brakes started working? What was different?
Thanks for the input.
"Situation diffused itself" = I didn't crash and drove sanely the rest of the way home.
Both brake fade and the check valve describe what's happening. I'm questioning the brake fade since the brakes were cool at the time I stood on them.
I remember it being just a hard pedal, with no antilock pulsing. The brake fade definition is very close to what I experienced. But the problem is when I stood on the brakes, I was on the highway for about 2 miles with very little braking prior. The brakes would have been very cool at that time.

The check-valve makes sense also. I'll look into replacing that first.

Last edited by Lotsokids; 06-14-2018 at 08:12 AM.
Lotsokids is offline  
Reply With Quote
Old 06-18-2018, 11:14 AM
  #10  
FNLGOT1
Junior Member
 
Member Since: Aug 2000
Location: Lombard IL
Posts: 39
Thanks: 0
Thanked 0 Times in 0 Posts
Default

I'm wondering why didn't the ABS activate?
FNLGOT1 is offline  
Reply With Quote
Old 06-18-2018, 11:49 AM
  #11  
Millenium Z06
CF Senior Member
 
Millenium Z06's Avatar
 
Member Since: Jun 2004
Location: Frisco TX Pants Shitingly Fast
Posts: 4,877
Thanked 115 Times in 102 Posts
Default

Originally Posted by FNLGOT1 View Post
I'm wondering why didn't the ABS activate?
Because the wheels weren't locked up maybe..
Millenium Z06 is online now  
Reply With Quote
Old 06-18-2018, 11:54 AM
  #12  
Millenium Z06
CF Senior Member
 
Millenium Z06's Avatar
 
Member Since: Jun 2004
Location: Frisco TX Pants Shitingly Fast
Posts: 4,877
Thanked 115 Times in 102 Posts
Default

Originally Posted by Lotsokids View Post
Thanks for the input.
"Situation diffused itself" = I didn't crash and drove sanely the rest of the way home.
Both brake fade and the check valve describe what's happening. I'm questioning the brake fade since the brakes were cool at the time I stood on them.
I remember it being just a hard pedal, with no antilock pulsing. The brake fade definition is very close to what I experienced. But the problem is when I stood on the brakes, I was on the highway for about 2 miles with very little braking prior. The brakes would have been very cool at that time.

The check-valve makes sense also. I'll look into replacing that first.
A hard brake pedal makes me think brake booster check valve.
Roll the windows down or at least the drivers, drive at regular speeds, 35mph or so and preferably parallel to a wall.
Let off the accelerator pedal and listen for a very light whistling. If you hear it, check the brake booster check valve and specifically the grommet that surrounds it in the brake booster.

Mine had a small gap on the driver side of the grommet from the hose connecting to the back of the intake pulling on it. Its about $3.00 at O'Riley's
Millenium Z06 is online now  
Reply With Quote
The Following User Says Thank You to Millenium Z06 For This Useful Post:
Lotsokids (06-18-2018)
Old 06-18-2018, 03:14 PM
  #13  
Lotsokids
Junior Member
Thread Starter
 
Lotsokids's Avatar
 
Member Since: Dec 2017
Location: Moore Oklahoma
Posts: 23
Thanked 2 Times in 2 Posts
Default

Originally Posted by Millenium Z06 View Post
A hard brake pedal makes me think brake booster check valve.
Roll the windows down or at least the drivers, drive at regular speeds, 35mph or so and preferably parallel to a wall.
Let off the accelerator pedal and listen for a very light whistling. If you hear it, check the brake booster check valve and specifically the grommet that surrounds it in the brake booster.

Mine had a small gap on the driver side of the grommet from the hose connecting to the back of the intake pulling on it. Its about $3.00 at O'Riley's
Thanks for the input. I purchased a new OEM check valve, and will install it soon.
Then maybe a test on an empty highway with nothing around.
Lotsokids is offline  
Reply With Quote
Old 06-18-2018, 09:29 PM
  #14  
RobJoy
CF Senior Member
 
RobJoy's Avatar
 
Member Since: Nov 2013
Location: western NC
Posts: 281
Thanked 18 Times in 17 Posts
Default

Originally Posted by Lotsokids View Post
Thanks for the input. I purchased a new OEM check valve, and will install it soon.
Then maybe a test on an empty highway with nothing around.
1. If you don't want to get too fast you may try flooring the gas at low speed while in one of the higher gears so pedal can be held down long enough to simulate the event when brake problem occurred. This should drop intake vacuum considerably.
2. Just curious. Do you have a radical camshaft? Radical cams can reduce intake vacuum considerably. I had a hot rod several years ago with such a cam and I could get only about one brake pedal depression before the booster vacuum was used up. I installed a vacuum canister (from Jeg's) which increased my vacuum volume sufficiently to provide booster assistance for more than just the one brake pedal effort.

Last edited by RobJoy; 06-19-2018 at 03:24 PM. Reason: add
RobJoy is offline  
Reply With Quote
Old 06-19-2018, 11:38 AM
  #15  
Dutch08
CF Senior Member
 
Member Since: Sep 2014
Location: Atlanta GA
Posts: 716
Thanked 61 Times in 59 Posts
Default

Originally Posted by Lotsokids View Post
Yesterday I experienced something rather scary. I'll admit, I was aggressive and stupid. "Messed with" another vehicle, and down-shifted to third at about 65 MPH, and accelerated to the redline, then I braked hard as there were other cars on the highway. My car was not stopping very quickly, and I stood on the brakes. It felt like someone greased my rotors. It was VERY slow braking. The situation diffused, but was very unnerving. I attempted to brake hard again a few minutes later, and it felt fine. Pads and rotors appear fine. Driving to work this morning at about 50 MPH, I stood on the brakes, and it stopped immediately with slight chirping of the tires.
This is a VERY big problem if you cannot brake at high speed. Not sure what's going on.
Any ideas?
I had the same exact problem. I've tried to reproduce the problem but I can't. I'm guessing (based on the comments - Thank you to all) that's its vacuum on the brake booster from the sudden change from accel to the brakes. I've flushed my brake lines and inspected the brakes. Now I'll check the booster.
Dutch08 is online now  
Reply With Quote
Reply
 
 
 

Forum Jump

Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: