What is going on with my brakes? They really suck.
07-22-2010, 06:23 PM
#1
What is going on with my brakes? They really suck. Okay I have a full front and rear LS1 brake conversion and the braking power sucks. The LT1 brakes sucked even worse and I am now convinced their is a problem.
The brake pedal pushes in maybe an inch or two and gets hard as a rock. You have to push the Hell out of it to get decent stopping power in a panic situation.
I have compared the braking power to my truck, mini van and Accord. There is a problem here.
I really dont think the calipers, pads or rotors are a problem. I have bled them several times the best I can and I do not have any ABS lights. The booster seems to be doing its job so all thats really left is the master cylinder.
Can a bad master cylinder cause a firm pedal and lack of braking power? Any other suggestions?
The brake pedal pushes in maybe an inch or two and gets hard as a rock. You have to push the Hell out of it to get decent stopping power in a panic situation.
I have compared the braking power to my truck, mini van and Accord. There is a problem here.
I really dont think the calipers, pads or rotors are a problem. I have bled them several times the best I can and I do not have any ABS lights. The booster seems to be doing its job so all thats really left is the master cylinder.
Can a bad master cylinder cause a firm pedal and lack of braking power? Any other suggestions?
07-22-2010, 08:42 PM
#5
If I press the brake several times with the motor NOT running. It will firm up. If I hold the brake and start the motor, the brake pedal sinks like it should. The booster is definitely holding air, I confirmed that.
The few inches the pedal moves feels soft to me then it gets hard as a rock. The area of pedal of pedal travel before it gets rock hard provides very little braking power.
The few inches the pedal moves feels soft to me then it gets hard as a rock. The area of pedal of pedal travel before it gets rock hard provides very little braking power.
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07-23-2010, 07:48 AM
#10
Seems to be all of the time. I cant even really get them to lock up and have the ABS chirp. Drove a buddies WRX this morning and that is the way brakes should work. I am even now further convinced there is a problem and now I am resiting even driving it cause if I have to panic stop, I am fucked.
His pedal is not as soft as mine during its normal travel prior to it getting very hard.
I am trying to think this through. The several inches of travel must be the normal travel of the MC pistons which apply force. Once the pedal stops, that must be the end of the pistons travel and no more forece is available. **** I dont know what to do except put a MC on it. Should not cost too much.
His pedal is not as soft as mine during its normal travel prior to it getting very hard.
I am trying to think this through. The several inches of travel must be the normal travel of the MC pistons which apply force. Once the pedal stops, that must be the end of the pistons travel and no more forece is available. **** I dont know what to do except put a MC on it. Should not cost too much.
07-23-2010, 08:20 AM
#11
how badly do you want to keep the ABS? I ditched my ABS and I have the Bob Bishop/C5 up front and stock lt1 in back. the pedal is perfect now, i think the abs takes away some of that nice pedal feel. i too had the same problem with ABS. I could never get it to lock and get that ABS kicking in feeling. Really didn't feel right, so I ditched it.
07-23-2010, 09:28 AM
#13
there is a special procedure for bleeding the ABS and not sure if there is any special equipment involved. When I was going through all that on mine a few years back, i was doing a lot of searching how best to resolve it. I think you have to bleed the M/C, bleed the ABS block, then bleed the wheels and what I don't recall was if the dealer had to hook up some machine so that it could actuate the ABS during the bleeding process. Again not completely sure, worth a call to the dealer see if they can tell you how they would bleed the system.
i bought the SJM kit from the sponsors here and it's been solid for a few years.
i bought the SJM kit from the sponsors here and it's been solid for a few years.
07-23-2010, 10:38 AM
#14
there is a special procedure for bleeding the ABS and not sure if there is any special equipment involved. When I was going through all that on mine a few years back, i was doing a lot of searching how best to resolve it. I think you have to bleed the M/C, bleed the ABS block, then bleed the wheels and what I don't recall was if the dealer had to hook up some machine so that it could actuate the ABS during the bleeding process. Again not completely sure, worth a call to the dealer see if they can tell you how they would bleed the system.
i bought the SJM kit from the sponsors here and it's been solid for a few years.
i bought the SJM kit from the sponsors here and it's been solid for a few years.
I will call the dealer but I am sure their response will be "Uh, we have special stuff that must be used to get'r done" wheter its true or not. I am confident in saying when the system was dry, I did NOT bench bleed the MC prior to bleeding all of the corners. Maybe there is still an air bubble present which makes some sense.
07-23-2010, 11:23 AM
#16
bench bleed it for sure if you ran it dry. go to autozone and see if they will give you some of those little bench bleeding adapters, if not, i made my own and turned them into the master from hard lines.
also, i can look up the abs bleeding procedure in the service manual if you don't have one, let me know.
also, i can look up the abs bleeding procedure in the service manual if you don't have one, let me know.
07-23-2010, 11:29 AM
#17
Buddy of mine drove it and he thinks the hydros are fine and the pedal feels normal. He thinks the pads are ****. I have Napa Safety Stop (supposed top be some version of raybestos) that are about three years ago and the front left has an annoying squeak.
I have been wanting to replace them anyway so now would be a good time to rule the pads out before tearing the MC off.
Pad recommendations?
I have been wanting to replace them anyway so now would be a good time to rule the pads out before tearing the MC off.
Pad recommendations?
08-02-2010, 01:33 PM
#19
Okay I did some more diagnosing.
MAP @ engine idle = 17 on the scan master
MAP @ engine decelerating = 10 on the scan master
BAR = 30
For the record, I have a 224/230 cam so vacuum is worse than the stock cam which makes 12 MAP on the scan master.
Hard braking is much better if I don't push the clutch at the same time as the brake pedal (10 MAP).
Hard braking is worse when I push the clutch at the same time as the brake pedal (17 MAP).
Somehow this seems vacuum related. Results are the same regardless if I have a brake vacuum cannister installed or not.
Brake booster seems to pass all of the diagnostic tests.
Brake pedal feels just like the pedal in any other car.
Is there still a possibility that the booster could be bad?
MAP @ engine idle = 17 on the scan master
MAP @ engine decelerating = 10 on the scan master
BAR = 30
For the record, I have a 224/230 cam so vacuum is worse than the stock cam which makes 12 MAP on the scan master.
Hard braking is much better if I don't push the clutch at the same time as the brake pedal (10 MAP).
Hard braking is worse when I push the clutch at the same time as the brake pedal (17 MAP).
Somehow this seems vacuum related. Results are the same regardless if I have a brake vacuum cannister installed or not.
Brake booster seems to pass all of the diagnostic tests.
- Hold vaccum for hours. Goes psssst if you pull the check valve.
- Motor off, brake pedal goes down and then gets firmer with each new pump.
- Pedal sinks when the motor is started assuming the booster has no vaccum.
Brake pedal feels just like the pedal in any other car.
Is there still a possibility that the booster could be bad?
08-02-2010, 03:27 PM
#20
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My brakes perform just like you describe yours and have for as long as I remember. I think you are on the right track trouble shooting the power assist. I'm tempted to replace my booster one of these days.
I just finished installing 4 wheel disc brakes on my 68 and they are nothing special GM pieces at the calipars, pads, and rotors, but I did get a dual diaphram 9" booster and this car stops much better than my T/A. The 68's pedal feel is just right, perhaps even a bit touchy which is last way I would describe the T/A pedal. I know our original boosters are smaller but I'm begining to think they are single diaphram or just junk. Perhaps they don't leak vacuum but the diaphram is old and stiff.
I just finished installing 4 wheel disc brakes on my 68 and they are nothing special GM pieces at the calipars, pads, and rotors, but I did get a dual diaphram 9" booster and this car stops much better than my T/A. The 68's pedal feel is just right, perhaps even a bit touchy which is last way I would describe the T/A pedal. I know our original boosters are smaller but I'm begining to think they are single diaphram or just junk. Perhaps they don't leak vacuum but the diaphram is old and stiff.