No brake pedal
09-10-2016, 03:38 PM
#1
No brake pedal
1974, power brakes. Pedal goes to the floor and the brakes barely slow the car down. 15" of vacuum at idle, 25" at 2500 RPM. BLED ALL CALIPERS -no air in brake fluid. New pads and calipers. No leaks anywhere in the system. Any ideas? Bob
09-10-2016, 05:14 PM
#2
Race Director
Member Since: Apr 2011
Location: North of Toronto - Ontario
Posts: 10,850
Received 3,134 Likes
on
2,068 Posts
What method did you use to bleed the brakes?
Did they used to work before?
M
Did they used to work before?
M
09-10-2016, 05:25 PM
#3
1. Brake hoses are expanding
2. Trapped air behind the caliper pistons.
3. Trapped air in the master cylinder.
4. master cylinder isn't moving enough fluid.
#1 you will see the hose expand
#2 force the pistons into the caliper and bleed again
#3 remove the master cylinder cap and slowly pump the brakes you should see a fountain of fluid as you slowly pump the brakes.
#4 same as #3 if you don't see a fountain of fluid then start looking at the master cylinder.
09-10-2016, 05:25 PM
#4
Pump the pedal, crack the bleeder. Many times. No air bubbles. Don't know if they worked before, just got the car. Every part, caliper, line etc was replaced. But, I think it's the orig master cyl
09-10-2016, 05:31 PM
#5
Drifting
OP, I hear you. I know how you feel. All I can say is that I was absolutely floored by how many big jugs I had to wash through my brake system before it was properly bled. Many. Like, 5. 2 to a crappy bleed and 3 to a proper gravity bleed.
The bubbles are very small. I used clear vinyl line attached to my bleeders and saw those stupid little bubbles just keep coming. I trusted that they would eventually stop, and they did.
It was a many-beer process.
I now have amazingly firm brakes that halts the car despite them being manual (not power). No pulls, no shimmies, and no soft pedal.
I would take YET ANOTHER look at your bleeding order and bleeding procedure.
Gravity bleed for the win.
I have to find the note I had on the order, but I BELIEVE it was drivers rear outer, then inner, then passenger rear outer, then inner, then passenger front, then driver front. That's a little different than the "furthest from the master cylinder first" method, but it came from a reliable source on this forum.
AND IT WORKED. So I won't question it.
I promise...it will work.
The bubbles are very small. I used clear vinyl line attached to my bleeders and saw those stupid little bubbles just keep coming. I trusted that they would eventually stop, and they did.
It was a many-beer process.
I now have amazingly firm brakes that halts the car despite them being manual (not power). No pulls, no shimmies, and no soft pedal.
I would take YET ANOTHER look at your bleeding order and bleeding procedure.
Gravity bleed for the win.
I have to find the note I had on the order, but I BELIEVE it was drivers rear outer, then inner, then passenger rear outer, then inner, then passenger front, then driver front. That's a little different than the "furthest from the master cylinder first" method, but it came from a reliable source on this forum.
AND IT WORKED. So I won't question it.
I promise...it will work.
09-10-2016, 05:33 PM
#6
Race Director
Member Since: Apr 2011
Location: North of Toronto - Ontario
Posts: 10,850
Received 3,134 Likes
on
2,068 Posts
As cagotzmann says, was there a good shot of fluid when you cracked the bleeders?
Also, did you do both bleeders on the rear calipers?
M
Also, did you do both bleeders on the rear calipers?
M
09-11-2016, 05:52 AM
#7
Racer
After the bleed, in the order listed above, brakes were amazing. Also i used mighty vac to bleed brakes by myself. Worked great.
09-11-2016, 06:33 AM
#8
Le Mans Master
If you have no leaks and no air bubbles when you bleed the brakes, then I would suspect the master cylinder for 3 reasons:
1. You state it may be original which is fine (mine is original) but it could be bad
2. If all the components in the brake system were replaced and the OEM master cylinder was not properly "bench bled" before refilling the system, you will have a very difficult time getting a proper brake pedal.
3. If the master cylinder is new and was not properly "bench bled" before install, see response #2.
I have said this before that the C3 system when all components are operating correctly and as factory specified are not hard to bled. The problem arises when something like weak/leaking caliper piston seals exist, rear rotor runout is out of spec, air leaks somewhere in the system, etc are occurring. If someone is going through 3-5 containers to bleed the brakes, something is not right or the procedure you are using is incorrect. I bleed out my brake fluid every 4-5 years to change it and go through maybe a large container of brake fluid, use the farthest from the master cylinder first method (pass rear), and have never bled my rear calipers except using the top bleeder (never have used the lower bleeders). the Car sits 99.99% of the time and I have never had a brake issue..............I have owned my car for 35 years and obviously have maintained it well. I think many brake problems occur with owners who have not owned the car for most of its life and have no idea how the brakes were maintained before the current ownership....
The only real issue with the C3 brake system was factory caliper piston cylinders rusting due to the non stainless steel finish. GM can be really dense though since they never addressed that issue and in fact, I had 2 early 90's chevy lumina eurosports which were the first 4 door mass market sedans from GM to have standard 4 wheel disc brakes and on both cars the rear calipers froze at about 80,000 miles with stuck RUSTED caliper pistons bores...GM never learns. The Lumina Eurosport also used the corvette composite rear transverse mono leaf spring just like the corvettes........great handling mass market sedan!
1. You state it may be original which is fine (mine is original) but it could be bad
2. If all the components in the brake system were replaced and the OEM master cylinder was not properly "bench bled" before refilling the system, you will have a very difficult time getting a proper brake pedal.
3. If the master cylinder is new and was not properly "bench bled" before install, see response #2.
I have said this before that the C3 system when all components are operating correctly and as factory specified are not hard to bled. The problem arises when something like weak/leaking caliper piston seals exist, rear rotor runout is out of spec, air leaks somewhere in the system, etc are occurring. If someone is going through 3-5 containers to bleed the brakes, something is not right or the procedure you are using is incorrect. I bleed out my brake fluid every 4-5 years to change it and go through maybe a large container of brake fluid, use the farthest from the master cylinder first method (pass rear), and have never bled my rear calipers except using the top bleeder (never have used the lower bleeders). the Car sits 99.99% of the time and I have never had a brake issue..............I have owned my car for 35 years and obviously have maintained it well. I think many brake problems occur with owners who have not owned the car for most of its life and have no idea how the brakes were maintained before the current ownership....
The only real issue with the C3 brake system was factory caliper piston cylinders rusting due to the non stainless steel finish. GM can be really dense though since they never addressed that issue and in fact, I had 2 early 90's chevy lumina eurosports which were the first 4 door mass market sedans from GM to have standard 4 wheel disc brakes and on both cars the rear calipers froze at about 80,000 miles with stuck RUSTED caliper pistons bores...GM never learns. The Lumina Eurosport also used the corvette composite rear transverse mono leaf spring just like the corvettes........great handling mass market sedan!
Last edited by jb78L-82; 09-11-2016 at 06:45 AM.
09-11-2016, 08:11 AM
#9
Melting Slicks
No leaks, everything else is new, it has to be the master. Think about the original master for a moment. The piston has been using the same portion of the bore during normal use for a long time. Old fluid that has absorbed water sits in the unused portion of the bore and possibly corroded the bore. Now you push the piston into the corroded bore when you bottom out the brake pedal bleeding the calipers, and the master seals are damaged.
09-11-2016, 09:30 AM
#10
Racer
Can you please verify your method..etc...
OP, I hear you. I know how you feel. All I can say is that I was absolutely floored by how many big jugs I had to wash through my brake system before it was properly bled. Many. Like, 5. 2 to a crappy bleed and 3 to a proper gravity bleed.
The bubbles are very small. I used clear vinyl line attached to my bleeders and saw those stupid little bubbles just keep coming. I trusted that they would eventually stop, and they did.
It was a many-beer process.
I now have amazingly firm brakes that halts the car despite them being manual (not power). No pulls, no shimmies, and no soft pedal.
I would take YET ANOTHER look at your bleeding order and bleeding procedure.
Gravity bleed for the win.
I have to find the note I had on the order, but I BELIEVE it was drivers rear outer, then inner, then passenger rear outer, then inner, then passenger front, then driver front. That's a little different than the "furthest from the master cylinder first" method, but it came from a reliable source on this forum.
AND IT WORKED. So I won't question it.
I promise...it will work.
The bubbles are very small. I used clear vinyl line attached to my bleeders and saw those stupid little bubbles just keep coming. I trusted that they would eventually stop, and they did.
It was a many-beer process.
I now have amazingly firm brakes that halts the car despite them being manual (not power). No pulls, no shimmies, and no soft pedal.
I would take YET ANOTHER look at your bleeding order and bleeding procedure.
Gravity bleed for the win.
I have to find the note I had on the order, but I BELIEVE it was drivers rear outer, then inner, then passenger rear outer, then inner, then passenger front, then driver front. That's a little different than the "furthest from the master cylinder first" method, but it came from a reliable source on this forum.
AND IT WORKED. So I won't question it.
I promise...it will work.
Thanks.....mk's78 aka Mike
09-12-2016, 10:31 AM
#12
Drifting
I stand happily corrected.
To confirm the bleed pattern that is directly from GM for our cars and was shared on this forum by a very respected technical source (don't remember who, but thanks!!!):
Left Rear Inner
Left Rear Outer
Right Rear Inner
Right Rear Outer
Right Front
Left Front
I use the gravity bleed method. Other than that, I've tried the "vaccu-suck" method and the maligned "up...down...up...down...up...down" method. Gravity bleed gave me a VERY, VERY high quality pedal. By far the best of the three FOR ME, but I'm far from an expert. I'm just a shade-tree car guy. With a lift.
Another trick was to "work" the caliper as it bled. The rears especially, but all enjoyed the sweet release of some love taps from a rubber mallet every few minutes. This released air bubbles from the internal wall of the caliper. I also physically "rock" the caliper as much as I can to work the pads around and open the pistons up a little. I was always rewarded with a nice little slug of bubbles in my tube every time I did these things. Once I got NO bubbles from my manipulation of the caliper and I got NO little-bitty-itsy-bitsy bubbles along the top of the tube, I knew I was OK to move on to the next bleeder.
As I said before, I know it sounds silly, but it took me a HUGE amount of fluid to drive out all the bubbles. Far more than just "replacing the fluid in the system". Honestly...I'd get 3 big jugs and plan on burning one full jug for each of the rear calipers. At least. I used every single drop of the 3 jugs before I was happy with my pedal. And I still had a (extremely) small stream of the very smallest of bubbles before I "called it" on each caliper. So I could actually get it a little better.
Hope this helps. Good luck to you!
To confirm the bleed pattern that is directly from GM for our cars and was shared on this forum by a very respected technical source (don't remember who, but thanks!!!):
Left Rear Inner
Left Rear Outer
Right Rear Inner
Right Rear Outer
Right Front
Left Front
I use the gravity bleed method. Other than that, I've tried the "vaccu-suck" method and the maligned "up...down...up...down...up...down" method. Gravity bleed gave me a VERY, VERY high quality pedal. By far the best of the three FOR ME, but I'm far from an expert. I'm just a shade-tree car guy. With a lift.
Another trick was to "work" the caliper as it bled. The rears especially, but all enjoyed the sweet release of some love taps from a rubber mallet every few minutes. This released air bubbles from the internal wall of the caliper. I also physically "rock" the caliper as much as I can to work the pads around and open the pistons up a little. I was always rewarded with a nice little slug of bubbles in my tube every time I did these things. Once I got NO bubbles from my manipulation of the caliper and I got NO little-bitty-itsy-bitsy bubbles along the top of the tube, I knew I was OK to move on to the next bleeder.
As I said before, I know it sounds silly, but it took me a HUGE amount of fluid to drive out all the bubbles. Far more than just "replacing the fluid in the system". Honestly...I'd get 3 big jugs and plan on burning one full jug for each of the rear calipers. At least. I used every single drop of the 3 jugs before I was happy with my pedal. And I still had a (extremely) small stream of the very smallest of bubbles before I "called it" on each caliper. So I could actually get it a little better.
Hope this helps. Good luck to you!
Last edited by keithinspace; 09-12-2016 at 10:33 AM.
The following users liked this post:
Cool bean (09-12-2016)
