Have you checked rod length from your old master to all the new ones you installed. Rod length into the master would increase as you press the pedal, the rod pushes the little cylinder like cups into cylinder of master. If there is a rod length difference, this would also cause this. I have seen some new masters where 2 rods are supplied one shorter, on stock length.
New EVERYTHING. Brakes STILL soft!
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Have you checked rod length from your old master to all the new ones you installed. Rod length into the master would increase as you press the pedal, the rod pushes the little cylinder like cups into cylinder of master. If there is a rod length difference, this would also cause this. I have seen some new masters where 2 rods are supplied one shorter, on stock length.
Red Regal T
Senior Member
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Travis.....in this application the rod is in the booster unless this is what you mean.
Originally posted by Red Regal T
Travis.....in this application the rod is in the booster unless this is what you mean.
You got it. That is where i am going.
John have you had any problems where the rod is shorter and not pushing the pistons in the cylinder far enough, as SPOT6 just did the conversion not to long ago. Also John side line a nice clean kit, been running my butt off, however i want one of your brake conversions.This brings up an intresting point.
The car I got the vacuum brakes off of was a mid-late 80's n/a regal. The MC I have is for an '86 Monte Carlo with a 305. The reason I bought the Monte Carlo MC was because my friend's monte master cylinder looked identical to the one I got off the reagal and just figured it was the same. I didnt know the exact year of the regal so I just bought the one for the monte carlo. I wonder if they are the same? Is there anyway to find out?
The car I got the vacuum brakes off of was a mid-late 80's n/a regal. The MC I have is for an '86 Monte Carlo with a 305. The reason I bought the Monte Carlo MC was because my friend's monte master cylinder looked identical to the one I got off the reagal and just figured it was the same. I didnt know the exact year of the regal so I just bought the one for the monte carlo. I wonder if they are the same? Is there anyway to find out?
Put a post in junkyard dogs. See what kind of feedback you get, i had only 1 problem like this, where the pedal was very low, no air only to find out the pushrod in the booster was to short and was not pushing the pistons in the master far enough to build decent pressure.
turboman38
It costs money to go fast
- Joined
- Aug 1, 2001
- Messages
- 387
Sorry for not getting back to you sooner.
My instructions said to fill the MC with fluid and with both brake line holes in the master cylinder plugged with the bolt plugs provided push the piston in until it will not go any further. Crack the front bolt plug until no nore air comes out and then tighten the plug back up. Do this until you are not gaining any addition travel in the cylinder when pushing with the screw driver. Do the same for the rear plug. The piston got extremely difficult to push after the second sequence of bleeding on the second plug. The instructions then said that the piston travel should be no more than one quarter inch. Mine was an eighth of an inch.
I then installed the MC on the car and connected the lines on the MC. Had my wife pump the brake a couple times and then cracked the front line. You should get nothing but fluid. However BE VERY CAREFUL HERE. I cracked the line and went a liitle to far and brake fluid sprayed all over the fender. It would be a good idea to have a rag wrapped around the line. I did the same for the rear line and had good brakes at that point.
As I said before my cast iron proportioning valve was leaking so I replaced it with a brass one.
My instructions said to fill the MC with fluid and with both brake line holes in the master cylinder plugged with the bolt plugs provided push the piston in until it will not go any further. Crack the front bolt plug until no nore air comes out and then tighten the plug back up. Do this until you are not gaining any addition travel in the cylinder when pushing with the screw driver. Do the same for the rear plug. The piston got extremely difficult to push after the second sequence of bleeding on the second plug. The instructions then said that the piston travel should be no more than one quarter inch. Mine was an eighth of an inch.
I then installed the MC on the car and connected the lines on the MC. Had my wife pump the brake a couple times and then cracked the front line. You should get nothing but fluid. However BE VERY CAREFUL HERE. I cracked the line and went a liitle to far and brake fluid sprayed all over the fender. It would be a good idea to have a rag wrapped around the line. I did the same for the rear line and had good brakes at that point.
As I said before my cast iron proportioning valve was leaking so I replaced it with a brass one.
Red Regal T
Senior Member
- Joined
- May 24, 2001
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Not to correct you but that's not a good way to bleed the MC. When using the method of running hoses, off the fittings, back into the MC reservoir, you can see the air bubbles rising to the surface as you push in the plunger. While you were successful with the method you describe, it's pretty hit or miss. You want to know the MC is completely bled without question, expecially in this problem case.
I understand bench bleeding however, stick someone in the car. Pump them up crack the front line on master a little tighten. Pump them up crack the rear line on master. Do this a few times make sure master cap is on tight while braking the lines loose. Continue to do this until just fluid comes out make sure no air.
We also need to look into the length of push-rod on booster and make sure it is correct length.
We also need to look into the length of push-rod on booster and make sure it is correct length.
zam70, Yes, the pedal, booster, and MC were all off the same car and installed on my car.
How can I tell the length of the pushrod? Does the booster need to come off the car?
And also, if the pedal goes all the way down and stops, doesnt that mean that the piston on the MC is all the way in? So it wouldnt matter if the pushrod was the correct length because we already know the piston is all the way in. Unless there is something else that is stopping the pedal? It doesnt actually hit the carpet in the car, it stops about an inch short. I am assuming that it stops because the piston is all the way in....?
How can I tell the length of the pushrod? Does the booster need to come off the car?
And also, if the pedal goes all the way down and stops, doesnt that mean that the piston on the MC is all the way in? So it wouldnt matter if the pushrod was the correct length because we already know the piston is all the way in. Unless there is something else that is stopping the pedal? It doesnt actually hit the carpet in the car, it stops about an inch short. I am assuming that it stops because the piston is all the way in....?
Do not assume anything.
Yes pushrod in booster, it must be unbolted to inspect it. You said you have changed master cylinders. Did you buy a new one? Again you either still have air, pushrod not going in all the way, internal leak in master, booster bad. Did you rebleed master yet with someone in car pumping the hell out of it. When you pump it up, does it feel better with car off.
Yes pushrod in booster, it must be unbolted to inspect it. You said you have changed master cylinders. Did you buy a new one? Again you either still have air, pushrod not going in all the way, internal leak in master, booster bad. Did you rebleed master yet with someone in car pumping the hell out of it. When you pump it up, does it feel better with car off.
Well heres what I did:
I removed the MC and put it in a vise. I bought a few fittings and some clear hose. Put this fittings in the MC and the hose on the end of the fittings. I ran the hose into the MC and submerged them in brake fluid. I slowly pushed the piston all the way in, then slowly all the way out. I did this about 15 times. There was some air in the lines, but not much. I removed the MC from the vise and installed in on my car. I kept the fittings and lines on the MC and bolted the MC to the booster. After it was bolted to the booster, I went inside the car and pumped the brakes slowly all the way to the bottom and all the way to the top. I was able to see the clear lines and MC from inside the car and was able to watch for bubbles. I just wanted to make sure that they were all out of there. After a few pumps ensuring that there were ZERO bubbles, I removed the fittings and put the regular brake lines on. I am going to gravity bleed all the brakes now and will post back when I am finished.
The piston on the MC was hard to push in when doing it by hand. When it was installed on the car and still bleeding the MC, the pedal was soft and smooth. I hope this fixes the problem.
I cross-referenced the MC's and brake booster and they are the same part numbers. I am sure the booster is fine since the MC and booster came off the same car. The part number for the MC I have now is the same part number as the one for the Regal I got it off of.
The MC I have now is a remanufactured unit.
Ill post back.
I removed the MC and put it in a vise. I bought a few fittings and some clear hose. Put this fittings in the MC and the hose on the end of the fittings. I ran the hose into the MC and submerged them in brake fluid. I slowly pushed the piston all the way in, then slowly all the way out. I did this about 15 times. There was some air in the lines, but not much. I removed the MC from the vise and installed in on my car. I kept the fittings and lines on the MC and bolted the MC to the booster. After it was bolted to the booster, I went inside the car and pumped the brakes slowly all the way to the bottom and all the way to the top. I was able to see the clear lines and MC from inside the car and was able to watch for bubbles. I just wanted to make sure that they were all out of there. After a few pumps ensuring that there were ZERO bubbles, I removed the fittings and put the regular brake lines on. I am going to gravity bleed all the brakes now and will post back when I am finished.
The piston on the MC was hard to push in when doing it by hand. When it was installed on the car and still bleeding the MC, the pedal was soft and smooth. I hope this fixes the problem.
I cross-referenced the MC's and brake booster and they are the same part numbers. I am sure the booster is fine since the MC and booster came off the same car. The part number for the MC I have now is the same part number as the one for the Regal I got it off of.
The MC I have now is a remanufactured unit.
Ill post back.
Sorry man if you've dealt with the brakes as many times as I have and bled them as many times as I have, you forget what the hell you are doing. So I dont need to re-bleed the MC do I because I let it go dry when bleeding the brakes? I hope not
BTW, thanks for sticking with this post while I do this crap.
BTW, thanks for sticking with this post while I do this crap.
Update:
I replaced the factory proportioning valve with the new GM brass vavle.
I bench bled the MC AGAIN (because I let it go dry once on accident). I put the MC back on the car and pumped the brakes a few more times with the lines still on it from bench bleeding just to make sure there was no air bubbles. It was pure fluid so the MC was bled properly.
I hooked up the brake lines to the MC and gravity bled each brake for a good 20 mins (about half of the MC was used for each wheel).
I then had a helper pump the brakes for me, and cracked each fitting open 5 times in the order of (RR, RF, LR, LF). The brakes were firmer.
I repeated the proccess again all the way around the car. When the car was off, the brake pedal was extremely hard to push. I was able to get 2 inches of travel at the very most.
I thought for sure they would be perfect. I fired the car up, and with the help of the vacuum from the motor I was ONCE AGAIN able to push the pedal to the floor with just a little bit of effort.
With S-10 wheel cylinders, I am able to only hold 0 until the car will push. This is CRAP.
New MC
New calipers
New factory proportioning valve
New front pads
Rotors cut
Drums cut
New rear shoes
No leaks from ANY of the fittings. I pushed the brakes as hard as I possibly could when the car was off to TRY to push fluid out of one of the fittings, and not one of them leaked at all.
I just dont understand this. There is only one more thing left. I have spent enough time and money on these brakes as it is, so Im going to replace the rear wheel cylinders again. They are 2 years old now. Maybe the guy at the parts counter grabed the wrong ones and I dont actually have the S-10 cylinders (for manual 7/8" brakes like I asked for).
njturbo, was the order I used ok? Does it matter if I do it RR, RF, LR, LF as opposed to your order (RR, LF, RF, LR)?
I replaced the factory proportioning valve with the new GM brass vavle.
I bench bled the MC AGAIN (because I let it go dry once on accident). I put the MC back on the car and pumped the brakes a few more times with the lines still on it from bench bleeding just to make sure there was no air bubbles. It was pure fluid so the MC was bled properly.
I hooked up the brake lines to the MC and gravity bled each brake for a good 20 mins (about half of the MC was used for each wheel).
I then had a helper pump the brakes for me, and cracked each fitting open 5 times in the order of (RR, RF, LR, LF). The brakes were firmer.
I repeated the proccess again all the way around the car. When the car was off, the brake pedal was extremely hard to push. I was able to get 2 inches of travel at the very most.
I thought for sure they would be perfect. I fired the car up, and with the help of the vacuum from the motor I was ONCE AGAIN able to push the pedal to the floor with just a little bit of effort.
With S-10 wheel cylinders, I am able to only hold 0 until the car will push. This is CRAP.
New MC
New calipers
New factory proportioning valve
New front pads
Rotors cut
Drums cut
New rear shoes
No leaks from ANY of the fittings. I pushed the brakes as hard as I possibly could when the car was off to TRY to push fluid out of one of the fittings, and not one of them leaked at all.
I just dont understand this. There is only one more thing left. I have spent enough time and money on these brakes as it is, so Im going to replace the rear wheel cylinders again. They are 2 years old now. Maybe the guy at the parts counter grabed the wrong ones and I dont actually have the S-10 cylinders (for manual 7/8" brakes like I asked for).
njturbo, was the order I used ok? Does it matter if I do it RR, RF, LR, LF as opposed to your order (RR, LF, RF, LR)?
