brake issues, what I've done and going to do, any suggestions: RESOLVED
After replacing the combination valve(the terminal was loose and on the verge of breaking) and rebleeding I still had a dash light issue. Although I bench bleed per directions there must have been air left in the rear part because when I bled at the master the light went out. And the brakes work. Will have to add additional vacuum dhe to cam because at idle the brakes aren't what thet should be. Thanks to all. Pete and Nicholas
I’m hoping someone can help me out. Here’s what’s been done and the results. Converting a 2dr, 350 automatic that had 70 power drum to power disc. Bought a “complete” 71-72? setup used. Things I used from it were the spindles, caliper brackets, dust shields, booster, combination valve and lines from master cylinder to combination valve.
Purchased master(bench bled it), new rotors, bearings, disc brake calipers and pads. Bought used disc brake frame brackets for the new rubber hoses. Also had to purchase a new brake line for the left front, got it at NAPA, nothing special and bent it to fit myself.
Cleaned up used parts and painted all parts. Installed correctly and bled system but had trouble bleeding the rears and the brake dash light stayed on. Further inspection revealed a leaking left rear wheel cylinder. Purchased two new rear wheel cylinders and replaced the old ones. Rebled the lines with the help of a mechanic friend. Still the brake dash light does not go out(will go out if you unplug at combo valve). Read all the posts on TC with the consensus being the valve needs to be re-centered. Tried the drive and hit brakes hard, no luck. Tested booster by pumping with the car off and starting and feel the brake pedal move towards the floor, tested good. I also tried the Chilton(read the procedure in their book) method of turning the key to the on position open the bleeder valve of the first bled side(rears) and had someone depress the brake slowly. According to Chilton once the dash brake light goes out tighten the bleeder screw up and release the pedal. That method did not work. Also tried another suggestion mentioned here and that was to open the bleeder had depress the brake hard and fast then tighten the bleeder back down. You got it, no good!
Took the little rubber boot off the combo valve to find the tiny(and I mean tiny) little “button”. Depressed it although it didn’t depress very well or much. Tried cleaning it with brake clean hoping to free it up. That seemed to help a little. Still the brake dash light stays on. Still not sure the valve is working right. Going to try one sent to me by a fellow TC’er tonight.
Mechanic friend came over and tried to help again and thought the booster was bad. He said it didn’t feel like the brakes were getting the “assist” they should be getting from the booster. Got a booster from NAPA only it had the long pushrod for power drums and not the short one for power discs. Due to design differences I could not swap out my pushrod for the one that came with the new booster. Hopefully they can resolve that issue shortly.
I borrowed a vacuum gage to find out at idle there is only 8-10 pounds of pressure. This is in park and not in gear(MC currently is off booster as going to try to and replace the booster). Vacuum tested the metal line coming off the intake that goes to the check valve on the booster. That line comes off a T fitting in the intake.
My main concern is getting the brakes to function properly, which means getting the dash light off. The “assist” issue is secondary and doesn’t affect the brake light, right? Two things I haven’t done that I’ve read is test to make sure front and rear brakes are working. Plan on doing that this evening. Going to jack the car up by the frame under the drivers door, put the car in neutral and have someone(daughter) apply the brakes as I spin the tires to make sure the front and rear brakes are functioning correctly. Also going to try and have someone(son) depress the “little button”(using a C-clamp on this I don’t believe will work) on the front of the combo valve and re-bleed the system. Right rear first the left rear, then right front, then left front and then have the helper(young son) release the pressure on the combo valve button. I tested the hard vacuum line that comes off the T in the intake. With the cam(no idea of specs) there is 8-10 lbs pressure that as the rpms are increased it raises as well.
A question, I just talked to NAPA and they asked what year master cylinder I had(I think 71 will check when I get home tonight). They tell me the booster is different from 70 to 71-72. They state that the booster from 67-70, is the same and changed in 701 Is this right?
I think I’ve covered it all. Any and all help would be appreciated. TIA Pete and Nicholas
After replacing the combination valve(the terminal was loose and on the verge of breaking) and rebleeding I still had a dash light issue. Although I bench bleed per directions there must have been air left in the rear part because when I bled at the master the light went out. And the brakes work. Will have to add additional vacuum dhe to cam because at idle the brakes aren't what thet should be. Thanks to all. Pete and Nicholas
I’m hoping someone can help me out. Here’s what’s been done and the results. Converting a 2dr, 350 automatic that had 70 power drum to power disc. Bought a “complete” 71-72? setup used. Things I used from it were the spindles, caliper brackets, dust shields, booster, combination valve and lines from master cylinder to combination valve.
Purchased master(bench bled it), new rotors, bearings, disc brake calipers and pads. Bought used disc brake frame brackets for the new rubber hoses. Also had to purchase a new brake line for the left front, got it at NAPA, nothing special and bent it to fit myself.
Cleaned up used parts and painted all parts. Installed correctly and bled system but had trouble bleeding the rears and the brake dash light stayed on. Further inspection revealed a leaking left rear wheel cylinder. Purchased two new rear wheel cylinders and replaced the old ones. Rebled the lines with the help of a mechanic friend. Still the brake dash light does not go out(will go out if you unplug at combo valve). Read all the posts on TC with the consensus being the valve needs to be re-centered. Tried the drive and hit brakes hard, no luck. Tested booster by pumping with the car off and starting and feel the brake pedal move towards the floor, tested good. I also tried the Chilton(read the procedure in their book) method of turning the key to the on position open the bleeder valve of the first bled side(rears) and had someone depress the brake slowly. According to Chilton once the dash brake light goes out tighten the bleeder screw up and release the pedal. That method did not work. Also tried another suggestion mentioned here and that was to open the bleeder had depress the brake hard and fast then tighten the bleeder back down. You got it, no good!
Took the little rubber boot off the combo valve to find the tiny(and I mean tiny) little “button”. Depressed it although it didn’t depress very well or much. Tried cleaning it with brake clean hoping to free it up. That seemed to help a little. Still the brake dash light stays on. Still not sure the valve is working right. Going to try one sent to me by a fellow TC’er tonight.
Mechanic friend came over and tried to help again and thought the booster was bad. He said it didn’t feel like the brakes were getting the “assist” they should be getting from the booster. Got a booster from NAPA only it had the long pushrod for power drums and not the short one for power discs. Due to design differences I could not swap out my pushrod for the one that came with the new booster. Hopefully they can resolve that issue shortly.
I borrowed a vacuum gage to find out at idle there is only 8-10 pounds of pressure. This is in park and not in gear(MC currently is off booster as going to try to and replace the booster). Vacuum tested the metal line coming off the intake that goes to the check valve on the booster. That line comes off a T fitting in the intake.
My main concern is getting the brakes to function properly, which means getting the dash light off. The “assist” issue is secondary and doesn’t affect the brake light, right? Two things I haven’t done that I’ve read is test to make sure front and rear brakes are working. Plan on doing that this evening. Going to jack the car up by the frame under the drivers door, put the car in neutral and have someone(daughter) apply the brakes as I spin the tires to make sure the front and rear brakes are functioning correctly. Also going to try and have someone(son) depress the “little button”(using a C-clamp on this I don’t believe will work) on the front of the combo valve and re-bleed the system. Right rear first the left rear, then right front, then left front and then have the helper(young son) release the pressure on the combo valve button. I tested the hard vacuum line that comes off the T in the intake. With the cam(no idea of specs) there is 8-10 lbs pressure that as the rpms are increased it raises as well.
A question, I just talked to NAPA and they asked what year master cylinder I had(I think 71 will check when I get home tonight). They tell me the booster is different from 70 to 71-72. They state that the booster from 67-70, is the same and changed in 701 Is this right?
I think I’ve covered it all. Any and all help would be appreciated. TIA Pete and Nicholas
