C3 (1979) Brake Problem
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
C3 (1979) Brake Problem
Can anyone explain this brake problem on a 1979?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
Last edited by Paul L; Jul 3, 2007 at 06:26 AM.
Pro
Joined: Apr 2007
Posts: 528
Likes: 9
From: Grand Rapids Michigan
You could simply have low fluid. Open the master cyl and check it for level. Every bit as likely, your system has air in it from leaking caliper seals. You may not see fluid leaking out, but they are notorious for air and moisture bypassing the seals and undermining the breaks.
Bleed the brakes using new DOT 4 fluid with silicon which is resistant to moisture. Make sure you bleed all the old fluid through the system. Start bleeding with the rear pass side caliper (farthest away from the master cyl). Make sure you bleed both bleeders on each caliper. do not allow the master to get empty. Have a friend or two help you, or buy a power bleeder/bottle combo to keep new fluid running through the system. Bleeding the brakes is tricky on these cars because of the caliper design. You can't overbleed your brakes. Good luck!
Bleed the brakes using new DOT 4 fluid with silicon which is resistant to moisture. Make sure you bleed all the old fluid through the system. Start bleeding with the rear pass side caliper (farthest away from the master cyl). Make sure you bleed both bleeders on each caliper. do not allow the master to get empty. Have a friend or two help you, or buy a power bleeder/bottle combo to keep new fluid running through the system. Bleeding the brakes is tricky on these cars because of the caliper design. You can't overbleed your brakes. Good luck!
Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Can anyone explain this brake problem on a 1979?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
sounds like classic air pumping.
Are your calipers original?
Or ,at least, do they have original type seals?
Have you resurfaced your rotors lately?
If yes to any of these questions, do yourself a favor and get a set of "O" ring seals. The kits are carried by any number of venders.
There's a lengthy explanation as to why the originals would pump air. If your intetrested in the cause do a search here or at the NCRStech board.
Le Mans Master
Joined: Mar 2004
Posts: 7,473
Likes: 1,495
From: Little Rock AR
Master cylinder may be shot. No fluid loss and a mismatched front to rear balance. Maybe the master is having difficulty maintaining equal pressure because the fluid is bypassing the middle piston. If the M/C is old you may need to replace it.
Thats my guess anyway.
-Mark.
Thats my guess anyway.
-Mark.
Melting Slicks
Joined: Nov 2000
Posts: 2,507
Likes: 114
From: St. Louis Mo
Can anyone explain this brake problem on a 1979?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
I had noticed last Sunday that I thought my brakes seemed a bit spongy? Today the same thing happened so I made it home probably just in time. While I backed in the laneway there appeared to be little or no brakes. The dash brake light came on momentarily. Pumping the brakes restores pedal pressure again. From the shop manual it seems it could be air or the proportional valve for the front and rear systems. Strange, as the master cylinder reservoir level is very close to the top?
And later...
This afternoon I replaced the hoses leading from the carb outlet pipe to the power booster. One clamp was broken, it looked good but the screw tightening system didn’t engage. It must have been like that forever. The other clamps were all fairly loose, but I didn’t see any breaks in the hoses. I reassembled everything and started the car. Pumping the brakes I got equal resistance each time, then again I didn’t take it out of the laneway or put it in gear. The pedal travel could be normal, I’m not sure as I’m a bit paranoid now? The pedal does not go near the floor like when I backed into the laneway yesterday.
Following the GM manual, when the car is off, and after pumping the brakes more than three times to remove vacuum, there should be no more than 1.8” travel. Following this procedure the pedal had lots of resistance, more than when running, and there was 1.125” travel. There is no fluid on the ground, and a quick look at the calipers doesn’t indicate any leakage. The reservoir as mentioned is near the top. . So I don’t know what to think?
Thread Starter
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
It's my brother's car. I sold it to him in 2003 when I bought the 1967.
I just tried the car in his driveway. Pedal is pretty firm and high with the engine off. With engine on the pedal is low; I would say 1" from the carpet. Not good. That can be pumped up another inch or so to what I remember as "normal".
-SS calipers are about 15 years old so seals are suspect
-front rubber hoses are 9 years old; being alone I could not see if they were swelling under pedal pressure
-pads are organic with about 25,000 miles (perhaps past service life?)
-master cylinder (MC) is original 1979
-master cylinder reservoirs are down about 1/2" (due to pad wear?)
-fluid is DOT 5 (silicone)
It may be a combination of things. My inclination is to have it diagnosed by a professional (not me) rather than throwing time and parts at it. And make a decision as to who will do what with what parts. I don't mind re-doing one caliper with a $20 seal kit (if one is bad) but if one is gone the others will follow shortly. The master cylinder is a job I would not undertake.
I just tried the car in his driveway. Pedal is pretty firm and high with the engine off. With engine on the pedal is low; I would say 1" from the carpet. Not good. That can be pumped up another inch or so to what I remember as "normal".
-SS calipers are about 15 years old so seals are suspect
-front rubber hoses are 9 years old; being alone I could not see if they were swelling under pedal pressure
-pads are organic with about 25,000 miles (perhaps past service life?)
-master cylinder (MC) is original 1979
-master cylinder reservoirs are down about 1/2" (due to pad wear?)
-fluid is DOT 5 (silicone)
It may be a combination of things. My inclination is to have it diagnosed by a professional (not me) rather than throwing time and parts at it. And make a decision as to who will do what with what parts. I don't mind re-doing one caliper with a $20 seal kit (if one is bad) but if one is gone the others will follow shortly. The master cylinder is a job I would not undertake.
Racer
Joined: Mar 2005
Posts: 445
Likes: 0
From: SAN DIEGO(SANTEE) CA.
sounds like classic air pumping.
Are your calipers original?
Or ,at least, do they have original type seals?
Have you resurfaced your rotors lately?
If yes to any of these questions, do yourself a favor and get a set of "O" ring seals. The kits are carried by any number of venders.
There's a lengthy explanation as to why the originals would pump air. If your intetrested in the cause do a search here or at the NCRStech board.
Are your calipers original?
Or ,at least, do they have original type seals?
Have you resurfaced your rotors lately?
If yes to any of these questions, do yourself a favor and get a set of "O" ring seals. The kits are carried by any number of venders.
There's a lengthy explanation as to why the originals would pump air. If your intetrested in the cause do a search here or at the NCRStech board.
TIA
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Drifting
Joined: Sep 1999
Posts: 1,970
Likes: 91
Paragon reproductions
Bairs
Dr. Rebuild
Zip
I bought mine,(1995?), when the developer of the o-ring design sold direct. Zero Tolerance Inc.(ZTI). O-rings and aluminum pistons still working flawlessly, in my original, unsleeved calipers.
Was later sold to a company in Florida I believe. May have been VBP
Burning Brakes
Joined: Jun 2005
Posts: 764
Likes: 2
From: THE OLDER I GET THE BETTER I WAS! NORTHERN ONTARIO
Bleed the brakes using new DOT 4 fluid with silicon which is resistant to moisture. Make sure you bleed all the old fluid through the system. Start bleeding with the rear pass side caliper (farthest away from the master cyl). Make sure you bleed both bleeders on each caliper. do not allow the master to get empty
I had thge same thing happen on my 79 no leaks just had to bleed them & I did it twice to make sure all the old fluid is gone. My problem went away
I had thge same thing happen on my 79 no leaks just had to bleed them & I did it twice to make sure all the old fluid is gone. My problem went away
