Brake problem! Help!!!
Thread Starter
Instructor
Joined: Jan 2007
Posts: 109
Likes: 1
From: Huntsville, AL
Brake problem! Help!!!
I was going down the road and almost passed my turn, hit the brakes, car pulls to right, and has little braking power. My 66 has power brakes. This was after the car had been sitting for two weeks, and on my way to a show, then no brakes! I have replaced the master cylinder with a 67, and new rubber hoses, and checked the system for leaks, and made sure that the calipers were not frozen up on every wheel. Bench bled the new master cylinder, bled all four corners, and went for a drive to find the very same problem. Pads look good, rotors look good.....this is a mystery to me. Any help is much appreciated. BTW: Made sure that the lines were in the right position on the Master cylinder too.....any thoughts?????? THANKS!
Melting Slicks
Joined: Apr 2002
Posts: 3,098
Likes: 2,352
From: Allison Park, PA
Danny,
You may want to check out the other post from today titled "Brakes Pulling" - seems to be almost the identical problem you're having. I made the comment that the brake rotors may be "glazed" - happened to me several years ago. Check it out!!!
Tom
You may want to check out the other post from today titled "Brakes Pulling" - seems to be almost the identical problem you're having. I made the comment that the brake rotors may be "glazed" - happened to me several years ago. Check it out!!!
Tom
Instructor
Joined: Jun 2006
Posts: 223
Likes: 0
From: Merritt Island FL
Is the brake pedal still hard when you are trying to stop, or does it go to the floor???
Make sure there isn't a vacuum leak in the line going to the master cylinder.... They could be glazed too tho... Take the wheel off and hit up the rotors with a scotch brite pad. Then go out and try to make a series of hard stops (get up to 50-60mph, and hit the brakes HARD... but, don't come to a complete stop. Repeat).
Make sure there isn't a vacuum leak in the line going to the master cylinder.... They could be glazed too tho... Take the wheel off and hit up the rotors with a scotch brite pad. Then go out and try to make a series of hard stops (get up to 50-60mph, and hit the brakes HARD... but, don't come to a complete stop. Repeat).
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,923
From: Washington Michigan
The 1967 master cylinder was the ONLY year that the same part was used for both manual and power brakes, and it has a "deep" hole in the rear piston so the pedal pushrod won't fall out when used on a manual brake car; as a result, the booster-to-master cylinder pushrod for a '67 is a unique "long" pushrod.
If you left your '66 booster-to-master pushrod in place when you changed to a '67 master cylinder, it's the standard "short" pushrod used for power brake master cylinders with the "shallow" hole in the rear piston, so it's not able to depress the '67 "deep hole" rear piston far enough to provide adequate braking action.
If you left your '66 booster-to-master pushrod in place when you changed to a '67 master cylinder, it's the standard "short" pushrod used for power brake master cylinders with the "shallow" hole in the rear piston, so it's not able to depress the '67 "deep hole" rear piston far enough to provide adequate braking action.
Thread Starter
Instructor
Joined: Jan 2007
Posts: 109
Likes: 1
From: Huntsville, AL
Thanks for the replies! I have since replaced all four calipers, and still have the same problem. Now....how do I correct the pushrod problem. Should I get a '67 pushrod for the master cylinder? OR, I could get a manual brake master cylinder for the existing pushrod in place. I have been told that the dual bowl M/C is the same for the 66 and the 67, but has a smaller piston for the manual brake set up, and therefore produces more pressure, and gives better braking. THOUGHTS?
Melting Slicks
Joined: Jan 2007
Posts: 2,582
Likes: 150
From: York PA
Thanks for the replies! I have since replaced all four calipers, and still have the same problem. Now....how do I correct the pushrod problem. Should I get a '67 pushrod for the master cylinder? OR, I could get a manual brake master cylinder for the existing pushrod in place. I have been told that the dual bowl M/C is the same for the 66 and the 67, but has a smaller piston for the manual brake set up, and therefore produces more pressure, and gives better braking. THOUGHTS?
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
To recap:
Car sat for two weeks and you drove the car for the first time. The brakes were pulling to the right and no stopping power. How were the brakes prior to the two week layover?
You changed the master cylinder and had the same issue.
You installed new calipers and have the same issue.
So you've had two different master cylinders on the car and it reacts the same way? I'm not familiar with the different length pushrod but it seems if there's enough length difference to cause a loss of braking or low pedal, you should be able to feel that in the brake pedal free play adjustment, i.e., way too much play before the pushrod contacts the MC piston. You'd feel the pushrod problem in the driveway. You wouldn't have to drive it to know something was wrong.
You haven't indicated if the brakes work in the driveway, just after some period of driving.
If you've bled all the air in the lines and you don't find air on the next bleed, I'd guess you have had two defective master cylinders that are bypassing internally on your car or a bad booster.
That's only a guess. A little history on your car would be a help.
Car sat for two weeks and you drove the car for the first time. The brakes were pulling to the right and no stopping power. How were the brakes prior to the two week layover?
You changed the master cylinder and had the same issue.
You installed new calipers and have the same issue.
So you've had two different master cylinders on the car and it reacts the same way? I'm not familiar with the different length pushrod but it seems if there's enough length difference to cause a loss of braking or low pedal, you should be able to feel that in the brake pedal free play adjustment, i.e., way too much play before the pushrod contacts the MC piston. You'd feel the pushrod problem in the driveway. You wouldn't have to drive it to know something was wrong.
You haven't indicated if the brakes work in the driveway, just after some period of driving.
If you've bled all the air in the lines and you don't find air on the next bleed, I'd guess you have had two defective master cylinders that are bypassing internally on your car or a bad booster.
That's only a guess. A little history on your car would be a help.
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Thread Starter
Instructor
Joined: Jan 2007
Posts: 109
Likes: 1
From: Huntsville, AL
I don't have silicone fluid, DOT3. Today I replaced the rear hoses, and bled the system again. Still pulling, and about the same braking power. How do I check the booster??? The brakes do work in the driveway, and the symptoms are exactly the same as out on the road. The car stops fine under slower driving, and sometimes does not pull to the right, but as soon as I gain some speed (60-70 mph) and hit the brakes fairly hard, I get the pulling, and seems that the right rear stops harder than the other brakes. The right rear is the ONLY brake that can skid the car at all, and that was after replacing the rear hoses today. Again, thanks very much for all of your help! Maybe I should check the booster (don't know how) and maybe find a different push rod, or a different master cylinder?????
Instructor
Joined: Jun 2006
Posts: 223
Likes: 0
From: Merritt Island FL
I don't have silicone fluid, DOT3. Today I replaced the rear hoses, and bled the system again. Still pulling, and about the same braking power. How do I check the booster??? The brakes do work in the driveway, and the symptoms are exactly the same as out on the road. The car stops fine under slower driving, and sometimes does not pull to the right, but as soon as I gain some speed (60-70 mph) and hit the brakes fairly hard, I get the pulling, and seems that the right rear stops harder than the other brakes. The right rear is the ONLY brake that can skid the car at all, and that was after replacing the rear hoses today. Again, thanks very much for all of your help! Maybe I should check the booster (don't know how) and maybe find a different push rod, or a different master cylinder?????
Still sounds like a booster/vacuum problem..... But, I don't know the procedure to check a brake booster. :o Sorry.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
When you bleed the brakes, do you find air in the lines?
When you bleed the brakes, do you get a good surge of fluid and good quantity out of the bleeders on all wheels? This is assuming you're bleeding by pumping the pedal.
Is the pulling to the right coming from the rear wheel or the front?
Is your brake warning light on the dash working?
The only way I know to check a booster for no assist is to see if it's holding vacuum. It should hold overnight if you have no leaks. There's probably a better way to check one but I don't know what it is.
When you bleed the brakes, do you get a good surge of fluid and good quantity out of the bleeders on all wheels? This is assuming you're bleeding by pumping the pedal.
Is the pulling to the right coming from the rear wheel or the front?
Is your brake warning light on the dash working?
The only way I know to check a booster for no assist is to see if it's holding vacuum. It should hold overnight if you have no leaks. There's probably a better way to check one but I don't know what it is.
Le Mans Master
Joined: Sep 2003
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From: Norwalk ohio
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St. Jude Donor '15
The 1967 master cylinder was the ONLY year that the same part was used for both manual and power brakes, and it has a "deep" hole in the rear piston so the pedal pushrod won't fall out when used on a manual brake car; as a result, the booster-to-master cylinder pushrod for a '67 is a unique "long" pushrod.
If you left your '66 booster-to-master pushrod in place when you changed to a '67 master cylinder, it's the standard "short" pushrod used for power brake master cylinders with the "shallow" hole in the rear piston, so it's not able to depress the '67 "deep hole" rear piston far enough to provide adequate braking action.
If you left your '66 booster-to-master pushrod in place when you changed to a '67 master cylinder, it's the standard "short" pushrod used for power brake master cylinders with the "shallow" hole in the rear piston, so it's not able to depress the '67 "deep hole" rear piston far enough to provide adequate braking action.
Pro
Joined: Sep 2008
Posts: 682
Likes: 0
From: Manteo NC
Maybe a crimped damaged line?? I had one hidden when I replaced mine when I 1st got the car. Road debris was the cause. John Z is your best bet on here IMO. That guy knows EVERYTHING that is posed to him, amazing he can keep that much knowledge stored. New and improved O-ring calipers or the original type? Notorious for failure I hear.
Last edited by obx2323; Jun 10, 2009 at 08:29 AM.
Thread Starter
Instructor
Joined: Jan 2007
Posts: 109
Likes: 1
From: Huntsville, AL
Mike:
I get the pull from the right rear. I also get a good stream of fluid from the bleeders. I did not at first, but now I do after changing the rubber hoses. The right rear tire is the only one that will skid. since I am getting that on the right rear, then maybe the pushrod is depressing the M/C far enough. Now, maybe i do have a problem with the pads or rotors. They appear to be good, but maybe fluid got on them while doing all this work to the car. I did have air in the lines, but remember I first changed the master cylinder, then the hoses, then the calipers. It took a while to bleed them, but I have a good hard pedal. The pedal is always good and firm, but just don't stop the car the harder I push them at higher speeds. At lower speeds, the car does stop ok. They are definitely better since I changed the calipers and hoses, but still not satisfactory.
I get the pull from the right rear. I also get a good stream of fluid from the bleeders. I did not at first, but now I do after changing the rubber hoses. The right rear tire is the only one that will skid. since I am getting that on the right rear, then maybe the pushrod is depressing the M/C far enough. Now, maybe i do have a problem with the pads or rotors. They appear to be good, but maybe fluid got on them while doing all this work to the car. I did have air in the lines, but remember I first changed the master cylinder, then the hoses, then the calipers. It took a while to bleed them, but I have a good hard pedal. The pedal is always good and firm, but just don't stop the car the harder I push them at higher speeds. At lower speeds, the car does stop ok. They are definitely better since I changed the calipers and hoses, but still not satisfactory.
Team Owner
Joined: Mar 2003
Posts: 26,118
Likes: 1,874
From: Greenville, Indiana
If your brake warning light is working and isn't on, you have good fluid flow(pressure unknown) to the calipers and no air in the system, you just about have to have some greasy stuff on the pads but even at low speeds, you'd still experience a lack of brakes. I don't understand the low speed/high speed difference.
The hard pedal is good, assuming the booster is doing it's job. Even if it's not providing boost, the pedal can still be hard.
I guess I've never seen pads glazed to the point there was a noticeable loss of braking so I can't help there. Why not pull a wheel that won't lock and check for glaze and contaminants?
The hard pedal is good, assuming the booster is doing it's job. Even if it's not providing boost, the pedal can still be hard.
I guess I've never seen pads glazed to the point there was a noticeable loss of braking so I can't help there. Why not pull a wheel that won't lock and check for glaze and contaminants?
Thread Starter
Instructor
Joined: Jan 2007
Posts: 109
Likes: 1
From: Huntsville, AL
Mike: Thanks for all of your helpful information. I don't have a brake light on the '66 for indicating fluid, or air, and there is NO proportioning valve on the car..(that began in '67) The light only tells me that I have the lights on with the headlight doors closed. Can you recommend a rotor....aftermarket from autozone, or oriley? Or, I can order genuine Delco from THEPARTSLADI. Are aftermarket rotors good? I have been told to use OE organic pads, and not metallic or semi metallic pads for best results. I really don't know. Replacing pads and rotors is just about all I can do except for the metal lines. Everything else is new....oh except for the booster, and that seems to be working. Then again, there is the issue concerning the pushrod. I have adjusted it almost all the way out, and does not change anything. I don't know if the M/C is defective, but everything else has been done......very perplexing! Thanks for your replies....all of you guys THANKS!