'79 brakes--Help
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 1,101
Likes: 0
From: Little Rock, Arkansas usa Arkansas
'79 brakes--Help
I have bought a '79, that supposedly had a new master cylinder put in just before my purchase. When I drove it home. it had a good pedal, but after about 75 miles of interstate driving, I lost the firm pedal and now I have to push all the way to the floor to get the brakes to just grab a little. I have no effect when I pump the brakes, still a pedal to the floor. When I turn off the car and pump the pedal, I will get a firm pedal. But, turn the ignition and start, pedal goes to the floor.
Can someone tell me where to start and make a quess on what might have gone wrong.
thanks
Can someone tell me where to start and make a quess on what might have gone wrong.
thanks
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
It sounds like master cylinder problems. Since the car is new to you, though, I would do a complete brake inspection including checking for caliper leakage, brake pad condition, hoses, rotors and condition of fluid. You don't want to be driving around with the brakes in this condition. Good luck with your new ride. 
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
It sounds like master cylinder problems. Since the car is new to you, though, I would do a complete brake inspection including checking for caliper leakage, brake pad condition, hoses, rotors and condition of fluid. You don't want to be driving around with the brakes in this condition. Good luck with your new ride.
Take to a Competent brake specialist and get it looked over.IMO, If the seller put in a "New" MC he probably got the cheapest one he could. So, given that I wouldn't trust it. First thing to do is bleed the brakes and see if that helps or fixes the problem. If it doesn't then put on a "Really New" Delco MC, flush fill and bleed.
Tech Contributor
Joined: Aug 1999
Posts: 15,156
Likes: 3,965
From: Connecticut, USA
Take to a Competent brake specialist and get it looked over.IMO, If the seller put in a "New" MC he probably got the cheapest one he could. So, given that I wouldn't trust it. First thing to do is bleed the brakes and see if that helps or fixes the problem. If it doesn't then put on a "Really New" Delco MC, flush fill and bleed.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I have bought a '79, that supposedly had a new master cylinder put in just before my purchase. When I drove it home. it had a good pedal, but after about 75 miles of interstate driving, I lost the firm pedal and now I have to push all the way to the floor to get the brakes to just grab a little. I have no effect when I pump the brakes, still a pedal to the floor. When I turn off the car and pump the pedal, I will get a firm pedal. But, turn the ignition and start, pedal goes to the floor.
Can someone tell me where to start and make a quess on what might have gone wrong.
thanks
Can someone tell me where to start and make a quess on what might have gone wrong.
thanks
As stated above. Install new brake fluid. You might have old fluid with a certain amount of water in them.
Pro
Joined: Apr 2007
Posts: 528
Likes: 9
From: Grand Rapids Michigan
"New" master cylinders are notorious (from what I've read here) for being bad the day you buy them as they sit dry on the shelf for a long period and the seals inside them recede. A few guys buy a rebuild kit, along with there new MC and just rebuild it even though it's brand new.
Also new master cylinders must be "bench bled" to remove air from the myriad cavities that are in the body of the MC. Are you certain this was done? Or can you probably guess it wasn't?
I am doing the brakes on my '79 now. The brake job is done, but friday is the day where I am bleeding the whole system and putting through DOT 5 silicone based fluid. This will replace the glycol fluid in the system and hopefully give me a stiffer pedal. My MC and booster are fine, but the pedal is still too soft for my liking. Hopefully the new fluid will make a difference. If I were you I'd bleed the living heck out of your system and make sure you've run through all new fluid (whether it's DOT 5 or 4) and see if that helps.
Also new master cylinders must be "bench bled" to remove air from the myriad cavities that are in the body of the MC. Are you certain this was done? Or can you probably guess it wasn't?
I am doing the brakes on my '79 now. The brake job is done, but friday is the day where I am bleeding the whole system and putting through DOT 5 silicone based fluid. This will replace the glycol fluid in the system and hopefully give me a stiffer pedal. My MC and booster are fine, but the pedal is still too soft for my liking. Hopefully the new fluid will make a difference. If I were you I'd bleed the living heck out of your system and make sure you've run through all new fluid (whether it's DOT 5 or 4) and see if that helps.
