Front disc brakes not working

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7

74 dart sport

Kameron
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On my 74 dart sport , the front brakes do not seem to be working. Last night we took it out for a ride for the first time , and the brakes seemed lazy. When we got out of the car , the front disc brakes were still rusted over and were not warm at all. We bled the brakes and got a new master cylinder. The vacuum booster makes a funny noise when pressing on the brakes. Also there is a small leak in the top of the master cylinder, but is probably just a bad gasket. We do not think the brake calipers are grabbing the disks. Any ideas?
Thanks , Kameron (drums in the back)
 
Especially if your calipers have the phenolic pistons this is common for them to bind up. Get some with the stainless pistons and you will be fine. I would also visually inspect the steel lines to make sure one didn't get dinged flat.
 
You can rebuild calipers, and I did long ago on a 1982 Aries, but it can be a fuss, so most people today just swap in a rebuilt one since for some cars they are only ~$20. Check rockauto.
 
I rebuilt them when I was young and poor but they are cheap as complete rebuilds.

BTW, did you bench bleed the new MC? If not, then it needs to be done and done right, and then the whole system re-bled.

If the brake booster makes a sound like a quacking duck or a loon crying, that may be the air being pulled into the diaphragm on the inside, near where the brake rod comes out.
 
bench bleed the M/C, or just loop some soft lines back into the reservoir while its still in the car, push the brakes slowly. If it test OK, pull the caliper and the piston side pad. put a valve spring in there against the far pad and pump the pedal. The piston should extend against the spring and retract. If not, remove spring and blow the piston out and rebuild or replace. single loaded calipers are too cheap to rebuild yours unless its something you want to do for the experience.
 
If you still have the same problem after bench bleeding, the calipers are likely seized. That fluid leaking from the master cylinder is being forced out through the gasket. When the pedal is pressed, the fluid has to go somewhere if the calipers do not work.
 
Also too, FWIW, master cylinders don't necessarily HAVE to be bench bled. I always do it out of habit regardless, but the reason for it is because not all master cylinders sit on the car level. A lot of them bolt to the firewall at an angle, with the nose of the master cylinder in the air a few degrees.

As such, it is impossible to get all of the air out, because air will become trapped in the nose of the master cylinder.

However, if it sits level, or if you jack the rear end up to level it out, you can certainly bleed it on the car.
 
One other thing to check -- if the front flex hoses are old, they may have swollen shut inside.
 
They are the hoses that run from the hard lines off the frame to the calipers. There is also one that runs from the block on the rear axle to a bracket on the frame. If you replace them, do all three. They break down on the inside as said earlier and can act like a check valve either stopping fluid from going to or stopping the calipers from being released. Brake stuff is pretty cheap. If it was mine, I would do calipers, hoses and wheel cylinders too.
 
So the problem probably is that the rotors were more rusty than we thought. It seems like the rotors are really rusty right now but they are getting better each time we drive it
 
74 dart sport said:
So the problem probably is that the rotors were more rusty than we thought. It seems like the rotors are really rusty right now but they are getting better each time we drive it
Click to expand...

Keep an eye on those front pads because the rust is going to eat em up pretty quick if it's that bad.

The standard disclaimer is you shouldn't even be driving it like that.
 
I must go devil's advocate to counter the rust comments from spoiled CA/AZ guys. If true, people couldn't drive cars in the Rust Belt. My 1996 Voyager sat for a month outside with the front wheels off while I rebuilt the transmission, during this El Nino winter when we got a little rain, but more "drizzle" compared to what "rain" means when I grew up in FL.

The rotors were a bit rusty after that, but it quickly wore off. I think semi-metallic beats rust any day, but I have "ceramic" pads whatever that means (more marketing, no real definition) and one grinds steel with ceramics. The rear wheels stayed on, but the drum internals must have rusted because they would jam up, but forcing thru that freed them. A worse problem up north is that people park a car for a winter with the parking brake on and the rear shoes rust in place on the backing plate. You must retract them to get the drum to slide off, which takes some beating.
 
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