Brakes really weak

[Mason Moran]

Hey all. Just bought a 74 duster 225 auto. The brakes "work" but they're really weak. You need to put the pedal in the floor to get any stoppage. I checked the pads and they should be replaced and the fluid is really dirty but full. Do you think flushing the system and replacing pads and rotors will fix this? Also how do you get the rotors off because I couldn't figure it out. Thanks

 

[RustyRatRod]

Replacing the pads and shoes can help pedal height a little, but you describe a hydraulic issue. You should inspect all the brake hoses, there are two in the front and one in the rear. Both calipers. Remove the rear wheels and inspect behind the boots on the wheel cylinders by prying them back and looking for fluid. it should be dry behind the boots. Also look under the master cylinder for leaks and look inside as well. Look and find the master cylinder pushrod where it comes through the firewall. You may have to pull some insulation out of the way and look for wetness. There should be none.

Very simple and self explanatory to remove the calipers. Look at the bolts that hold those brackets on either end of the caliper. Take note of how the brackets are installed. Maybe take a picture. Remove the bolts and brackets. I use a large flat screwdriver to push the caliper piston all the way back before I remove the caliper. Makes it easier to remove and then you can install the new thicker pads.

Installation is the exact reverse.

 

[Jax_1975_Dart]

I’d start with bleeding the lines and adjusting the rear drums to the point where you struggle to spin the rear wheels (while in the air/jacked up off the ground). Adjusting the rear drums may be all that’s needed to get the pedal firmness back.

If adjusting rear drums and bleeding all 4 lines doesn’t bring back the pedal... next I’d consider replacing all 3 rubber hoses (2 fronts and 1 rear) and the front disc pads you already mentioned. Before tossing the rotors, check their thickness to see if they are still within spec.

 

[Mason Moran]

I figured out the calipers and pads, but how do i get the disc rotors off? Some of them are really badly grooved and should probably be replaced

 

[RustyRatRod]

I figured out the calipers and pads, but how do i get the disc rotors off? Some of them are really badly grooved and should probably be replaced

See that dust cap at the end of the rotor? Take a big pair of channel lock pliers and pop them off. There's a nut and cotter key. Self explanatory from there and if it's not, take it to a mechanic.

 

[67Dart273]

Hey all. Just bought a 74 duster

YOU ARE A PRIME CANDIDATE for a guy who needs a factory service manual. Unfortunately the latest you can get "free" at MyMopar is 73. That will help you with some stuff, but the wiring is quite different. Please do what it takes to get either a CD/DVD or reprint factory manual. There are two books, one for the body, one for the chassis.

 

[Mason Moran]

UPDATE: Started taking my rear brakes apart and I think I know why my brakes are soft. The wheel cylinders have practically disintegrated inside so I'm getting next to no braking power and I think I read that can make brakes soft too.
A dilemma: I ordered new springs, shoes, and wheel cylinders from auto zone and none of them are right. The shoes are too small, the springs aren't right, and the wheel cylinder pistons don't have a slot to put the fork catches inside. I don't really know how to explain it. Where can I buy parts that will be correct when I get them?

 

[Jax_1975_Dart]

I like Rock Auto (for their wider selection of brands and cheaper than most stores’ prices) but, any auto parts store should be able to sell you the right size brake components.

The trick here is to make sure you measure what’s installed on your vehicle so, that the new parts are an exact match. There’s usually more than one drum brake size configuration offered and measuring will save you from ordering the wrong sized parts.

 

[my68barracuda]

UPDATE: Started taking my rear brakes apart and I think I know why my brakes are soft. The wheel cylinders have practically disintegrated inside so I'm getting next to no braking power and I think I read that can make brakes soft too.
A dilemma: I ordered new springs, shoes, and wheel cylinders from auto zone and none of them are right. The shoes are too small, the springs aren't right, and the wheel cylinder pistons don't have a slot to put the fork catches inside. I don't really know how to explain it. Where can I buy parts that will be correct when I get them?

It is possible that the rear deferential/rear brake assemblies are not original to your car. Over 50 years or so components get swapped out.
Do you know the difference between a 7.25 an 8.25 and a 8.75? If not look into it and verify the parts store is providing parts to the correct axel.

 

[dartfreak75]

UPDATE: Started taking my rear brakes apart and I think I know why my brakes are soft. The wheel cylinders have practically disintegrated inside so I'm getting next to no braking power and I think I read that can make brakes soft too.
A dilemma: I ordered new springs, shoes, and wheel cylinders from auto zone and none of them are right. The shoes are too small, the springs aren't right, and the wheel cylinder pistons don't have a slot to put the fork catches inside. I don't really know how to explain it. Where can I buy parts that will be correct when I get them?

Is it a 7 1/4 rear end? I'm assuming so. Since its a slant. Let me look i think I have some newish wheel cylinders you can have for free. Pm me if interested.

 

[dartfreak75]

It is possible that the rear deferential/rear brake assemblies are not original to your car. Over 50 years or so components get swapped out.
Do you know the difference between a 7.25 an 8.25 and a 8.75? If not look into it and verify the parts store is providing parts to the correct axel.

Yea that's what I was thinking also I believe the later years had a larger drum. He may have got the early drum stuff. They had a 9 inch and 10 inch flavor its always confused me which came in what.?! I think the v8s had a different size that the slant 6 in certain years unless it had the heavy duty brake package. Maybe? Lol

 

[RustyRatRod]

UPDATE: Started taking my rear brakes apart and I think I know why my brakes are soft. The wheel cylinders have practically disintegrated inside so I'm getting next to no braking power and I think I read that can make brakes soft too.
A dilemma: I ordered new springs, shoes, and wheel cylinders from auto zone and none of them are right. The shoes are too small, the springs aren't right, and the wheel cylinder pistons don't have a slot to put the fork catches inside. I don't really know how to explain it. Where can I buy parts that will be correct when I get them?

You have to verify what you HAVE first, that way you can match it up and know what you are looking at. Since you make no mention of pads or rotors, I assume you have 4 wheel drum brakes? We need to know that, if we're expected to be of any help to you. There are 9" drum brakes and 10" drum brakes from the factory.

As stated though, these cars now are so old, there's no telling if it still has the factory brakes on it or not. You need to make that determination first.