Brakes on 1975 c3
Thread Starter
5th Gear
Joined: May 2013
Posts: 5
Likes: 0
Please help...brakes. 75... C3
Hello, this is my first ever forum involvement as I'm at the end of my rope. I hope someone can help me. I have just added new...master cylinder, brake lines, proportioning valve, calipers, pads. In other words everything is new from the mc to the rear. I can't get fluid to the rear, Either axle. I tried...gravity bleed, 2 person bleed, power bleed (using compressor), I even tried to bypass the proportioning valve and still no fluid to the rear. I ran the air hose thru to blow out line(dirt). I don't know what else to do. Could it be the booster? That's the only thing I haven't tried and i didn't want to throw away more unnecessary money. Any help would be greatly appreciated. Thanks in advance.
Last edited by Darkdude; May 13, 2013 at 01:24 AM.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Are you getting fluid out of the rear port on the master cylinder? The only thing I can think of is that somehow when you intalled it the rear piston is already depressed past the hole that allows the fluid to enter the piston. No amount of bleeding will work if fluid can't get into the piston. If you take the cover off the master cylinder and press the brake pedal, you should see the fluid move at the hole where it goes from the reservoir to the piston. That will at least tell you that the piston is moving.
Thread Starter
5th Gear
Joined: May 2013
Posts: 5
Likes: 0
I thought I was getting a decent amount of fluid to the rear when I used the pneumatic bleeder, but when I started the car and put it in gear(while it was on the lift) the rear tires would not stop when the pedal was pushed.
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,561
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
I'll guess that the master cylinder is bad.
You can re-bleed it on the car and see if there is an equal amount of fluid moving on each pump.
If not then leave the front bleed connected and plug the rear port.
If the pedal is not rock hard then the M/C is bad.
You can re-bleed it on the car and see if there is an equal amount of fluid moving on each pump.
If not then leave the front bleed connected and plug the rear port.
If the pedal is not rock hard then the M/C is bad.
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Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Since everything is all new it's possible that your pistons were back in the bore and need to be pushed up against the pads. Try slowly pumping the brake pedal and watching the level of fluid in the master cylinder. If it is getting lower then you either have a leak somewhere or the pistons are being pushed up against the pads. Don't let the reservoir in the master cylinder get empty or you will have to start over with bench bleeding.
Putting the car in gear with the rear suspension hanging isn't a good idea. The u-joints in the half shafts can bind.
Last edited by my 76 ray; May 13, 2013 at 04:34 PM.
Racer
Joined: Aug 2000
Posts: 434
Likes: 3
From: Cleveland Ohio
Check the adjustable push-rod that is in the brake booster that pushes on the master cylinder piston. Measure the distance on the master cylinder to the seat on the piston that it pushes on and then measure the rod and adjust. Check a manual for the correct clearance distance.
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,561
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Check the adjustable push-rod that is in the brake booster that pushes on the master cylinder piston. Measure the distance on the master cylinder to the seat on the piston that it pushes on and then measure the rod and adjust. Check a manual for the correct clearance distance.
Some of the M/C have a divot and some have a deeper hole and they don't work if swapped out.