Brake Pedal Feel
11-20-2019, 06:13 PM
#1
Brake Pedal Feel Seem to be having an issue with the brake pedal. Almost the entire brake system has been replaced, booster master and abs block. No codes and bled the lines several times. But man do you really have to push the pedal down to stop. What do y'all think?
11-21-2019, 07:32 AM
#2
If the hydraulic feel is normal, typically this sort of thing would happen when the calipers bind up. (Pins aren't lubricated, etc.)
Can you post all the parts you installed? Are you sure you have the right parts on the car? Did you check for any physical obstructions?
Can you post all the parts you installed? Are you sure you have the right parts on the car? Did you check for any physical obstructions?
11-21-2019, 02:03 PM
#5
Well he noticed the brakes felt bad and he was having issues with abs block (throwing codes), but replaced with oem. Only thing he did not replace was brake lines. My gm tech said he thinks that is probably the issue. I just purchased stainless steel brake lines and hopefully this will fix the issue. Brake system is stock except for slotted rotors.
11-21-2019, 06:05 PM
#6
I was having a similar problem with my '98 that has a little over 200K miles on it with 4-channel/traction control. I still have the issue, so I am chiming in more to see what you find. The car wasn't always like this, but gradually the brakes got weaker over time, despite new pads and rotors and even calipers. My car was an automatic, and it was starting to get to the point that if you didn't pay attention to keeping a firm foot on the brake pedal at an intersection, it would start creeping forward, as automatics do when you take your foot off the brake. Now, I say WAS an automatic, because I just completed an LS3 build and I converted it to a manual. The brakes work, where the car does not feel dangerous, but I upgraded to 14" 6-piston Wilwood fronts, and it should stop much more readily than it does. It still takes a firm foot on the pedal when you want haul it down from speed in a hurry.
I replaced the brake booster and front calipers (2 piston OEM) when it was still an auto, and that did not change much (calipers were definitely shot though). As part of the recent engine swap, I replaced the relatively new booster with another reman (no one sells them new) and put in a brand new master cylinder. The only thing left to try, is to bleed the ABS block, as that was open while the engine and subframe were out of the car (the front 2 brake lines are attached to the subframe). This takes a GM scan tool to cycle the ABS solenoids though, so I need to take to a shop that has this. I feel like a little bit of the air may have worked its way out, since braking feels a little better than when I first drove it after the swap, but that could just be me getting used to the heavy pedal.
One thing I did notice when I unscrewed the brake lines from the ABS block, is that the old brake fluid around the fittings appears to have dried almost like sap. I worry that if this "sap" is in the ABS block or in the brake lines, this may be restricting flow, and would require even more hardware to be replaced.
I replaced the brake booster and front calipers (2 piston OEM) when it was still an auto, and that did not change much (calipers were definitely shot though). As part of the recent engine swap, I replaced the relatively new booster with another reman (no one sells them new) and put in a brand new master cylinder. The only thing left to try, is to bleed the ABS block, as that was open while the engine and subframe were out of the car (the front 2 brake lines are attached to the subframe). This takes a GM scan tool to cycle the ABS solenoids though, so I need to take to a shop that has this. I feel like a little bit of the air may have worked its way out, since braking feels a little better than when I first drove it after the swap, but that could just be me getting used to the heavy pedal.
One thing I did notice when I unscrewed the brake lines from the ABS block, is that the old brake fluid around the fittings appears to have dried almost like sap. I worry that if this "sap" is in the ABS block or in the brake lines, this may be restricting flow, and would require even more hardware to be replaced.
11-21-2019, 06:22 PM
#7
If you have more pedal travel then normal and poor brake performance don't overlook the front wheel bearings (Hub), Extra bearing play can cause the brake pads to be pushed back further than normal leading to a lower pedal and also poor braking.
Trending Topics
11-21-2019, 06:26 PM
#9
FWIW, steel lines over rubber increases pedal feedback for stiffer pedal.
ABS block needs to be flushed and bled with GM Tech 2 tool to activate all the solenoids while bleeding from the calipers and refilling the reservoir.
Soft pedal could be cracked vacuum line running from the intake to booster. Big cams and vacuum leaks could have the same effect. Something to see manifold vacuum might help diagnose.
ABS block needs to be flushed and bled with GM Tech 2 tool to activate all the solenoids while bleeding from the calipers and refilling the reservoir.
Soft pedal could be cracked vacuum line running from the intake to booster. Big cams and vacuum leaks could have the same effect. Something to see manifold vacuum might help diagnose.
11-21-2019, 06:48 PM
#10
Ok I'm going to try and answer, elaborate, on issue. Cam was just installed but someone that has swapped cams numerous times. 227/233 tsp cam and 1 7/8 headers. It's a soft pedal, travels quite a bit before stopping and its holding. When I cut the car off and when restarting the car, I go to press the brake, it is down with basically no play in the pedal.
Hope that answers all the questions. My guy that did the work said he used dot 3 fluid.
Hope that answers all the questions. My guy that did the work said he used dot 3 fluid.
11-21-2019, 10:39 PM
#11
I'll bet your problem is bad slider pins and bushings in the caliper brackets. If you didn't change the caliper brackets (so you can get new bushings in there to replace the originals that MUST be flat-spotted by now at 200K miles), then it's definitely time.
11-21-2019, 11:43 PM
#12
Except that after that, I swapped to fixed 6-piston front calipers, so there aren't any slider pins. The rears could possibly have issues, but they got lubed pretty regularly, so they don't look bad. When I get home at night and I've been pushing it a little, the rear brakes are actually kicking out more heat than the fronts. This tells me that there is some kind of blockage or air in the front lines, or that Wilwood was not accurate in their claim that the brakes are sized to work with the factory master cylinder. I also forgot to note that I swapped all rubber lines front and rear for braided steel.
11-22-2019, 06:38 AM
#13
If the total surface area of the aftermarket pistons is greater than the total surface area of the stock pistons in the calipers, then braking force at the pedal will definitely go up!
11-22-2019, 06:42 AM
#14
11-22-2019, 08:36 AM
#15
If this person knows what they are doing, then why do you have a problem and why are you posting here about it? Do you have some liability for the job (ie: did you pick out parts or go against some recommendations?) Or are you looking to be helpful to your mechanic's process or make sure you aren't taken for a ride on extra charges? (This info will probably help us respond more constructively.)
11-23-2019, 08:20 AM
#16
OK. We have a reputable mechanic who can't figure it out. 
I expect that if he fixes the problem for free, he'll stay reputable?
At the point you are replacing everything and making a big investment in the car, it's probably not a bad idea to replace the lines. (I don't think that's the problem, though.) Making sure the ABS module is properly bled is also a good idea.
Have you tried jacking a corner of the car up, taking a wheel off, and watching one of the front calipers actuate while someone applies the brakes? If you have a bind or a mechanical problem, you may see odd things like this.
I expect that if he fixes the problem for free, he'll stay reputable?At the point you are replacing everything and making a big investment in the car, it's probably not a bad idea to replace the lines. (I don't think that's the problem, though.) Making sure the ABS module is properly bled is also a good idea.
Have you tried jacking a corner of the car up, taking a wheel off, and watching one of the front calipers actuate while someone applies the brakes? If you have a bind or a mechanical problem, you may see odd things like this.
11-23-2019, 01:55 PM
#17
Good chance there is air in the lines. It can be difficult to get out after replacing parts. Best way is to bleed all the way around, drive it and mash pedal hard to activate and, on gravel or dirt if possible, several times. Hi back and bleed again, and repeat a couple times.
11-23-2019, 06:45 PM
#18
Good chance there is air in the lines. It can be difficult to get out after replacing parts. Best way is to bleed all the way around, drive it and mash pedal hard to activate and, on gravel or dirt if possible, several times. Hi back and bleed again, and repeat a couple times.
11-25-2019, 12:20 AM
#19
TECH Resident
Before I did anything else I'd get it bled with a scanner that can cycle the ABS. I've bled brakes many times without cycling the ABS and had no issue, but never with a brand new valve body.
11-25-2019, 02:31 AM
#20
I think this is a really interesting point. You can figure this out easily by yourself.
If the total surface area of the aftermarket pistons is greater than the total surface area of the stock pistons in the calipers, then braking force at the pedal will definitely go up!
If the total surface area of the aftermarket pistons is greater than the total surface area of the stock pistons in the calipers, then braking force at the pedal will definitely go up!