Brake help please

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Shamrock--WV2NC

Shamrock--WV2NC

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74 Dart has drums in the rear and disc up front. I changed pads rotors and calipers up front on my 74 dart with power brakes. i took for a test drive. After about 7 miles I smelled smoke. A 1/2 mile later I could tell I was driving with the front brakes engaged. I let the rotors cool off and drive home. Trying not to use the brake. So I let it cool overnight. Next day I go out and jack up car to make sure the wheels don't have drag. Everything seems good. I give it another try. I go for a little drive using the brakes often to give them a good test. And about 5 miles in I can feel the brakes. I come to a complete stop without using the pedal. I let rotors cool for about an hour than ease home. What is the diagnosis?
 
Shamrock--WV2NC said:
74 Dart has drums in the rear and disc up front. I changed pads rotors and calipers up front on my 74 dart with power brakes. i took for a test drive. After about 7 miles I smelled smoke. A 1/2 mile later I could tell I was driving with the front brakes engaged. I let the rotors cool off and drive home. Trying not to use the brake. So I let it cool overnight. Next day I go out and jack up car to make sure the wheels don't have drag. Everything seems good. I give it another try. I go for a little drive using the brakes often to give them a good test. And about 5 miles in I can feel the brakes. I come to a complete stop without using the pedal. I let rotors cool for about an hour than ease home. What is the diagnosis?
Click to expand...
My guess would be that the caliper pistons aren't releasing enough after you let go of the brakes and it begins to drag. As it begins to drag it heats up, the metal expands, and the drag increases even more, heats up even more, etc.

First, make sure the disc isn't cocked. Second, check the caliper.
 
A VERY common cause of this is mismatched parts at the master cylinder, causing the master piston to "not return" fully. This does not uncover the ports in the top of the bores of the master, causing pressure to be held

A quick way is to pump up the brakes, and with one wheel jacked up, if it is obviously dragging, take a rag/ container, and crack the nuts at the master........see if there is fluid released, and if the tire then frees up
 
One of two things.

Either the pistons are seized or too tight in the bores (usually on old calipers) and drag causing heating and expansion of the pads and rotors resulting in drag or, as stated above, the master cylindere cylinder pushrod is too long and holding the piston slightly depressed, blocking the port in the master cylinder which allows fluid to return to the reservoir.
 
I'm going to have to call master cyl push rod is to long, unbolt the master cyl and see if it pops out of the booster. It should be a nice fit and not pull in when you bolt it on. Or it could be the rod from the pedal to the booster is to long.
 
d55dave said:
One of two things.

Either the pistons are seized or too tight in the bores (usually on old calipers) and drag causing heating and expansion of the pads and rotors resulting in drag or, as stated above, the master cylindere cylinder pushrod is too long and holding the piston slightly depressed, blocking the port in the master cylinder which allows fluid to return to the reservoir.
Click to expand...
One of your rubber flex lines (or both) could have a blockage internally causing the new caliper to not release properly? If you jack it up when there hot and hanging up, check to see if one or both wheels wont turn check the flex lines on the calipers They may look fine on the outside , but have internal damage you cant see
 
So you are saying that it had power brakes before with no problems and all you did was change the pads, calipers, and rotors correct.
 
Yes it had power brakes before. I've never driven a long distance with the car. I'm talking 10 miles at a time.

Here's why I changed pads rotors calipers:
Start of drive would be fine and brakes worked. After a few miles, the car would get a vibration. The brakes would be very soft with the vibration really noticeable in the pedal.

I bought rotors, pads. When I tried to put them on both sides the piston would not go in. Got new calipers. Install went great.
You know the rest of the story
 
Shamrock--WV2NC said:
Yes it had power brakes before. I've never driven a long distance with the car. I'm talking 10 miles at a time.

Here's why I changed pads rotors calipers:
Start of drive would be fine and brakes worked. After a few miles, the car would get a vibration. The brakes would be very soft with the vibration really noticeable in the pedal.

I bought rotors, pads. When I tried to put them on both sides the piston would not go in. Got new calipers. Install went great.
You know the rest of the story
Click to expand...
I would change flexible rubber brake lines at calipers, bleed front brakes and try that
 
I have seen hoses go bad, the inside of the hose collapses, not letting fluid return. If the hoses look bad, replace them, as in the car needs them anyway. the pushrod idea makes sense if it appears to have some drum brake to disc brake swap going on. How else would a "longer pushrod " get into the car. I am not 100% sure, but Didnt 74 A bodies come standard with Disc Brakes? My train of though and experience is go with the simple things first, and I have seen hoses cause calipers to stick. The OP put "new calipers" on. the pistons are already collapsed, he or she wouldn't know if the hoses were restricted, as the fluid flows one way when the inside of the hose goes bad. Not saying dont go after the MC, but replace the hoses first, alot easier and least expensive.
 
Shamrock--WV2NC said:
Yes it had power brakes before. I've never driven a long distance with the car. I'm talking 10 miles at a time.

Here's why I changed pads rotors calipers:
Start of drive would be fine and brakes worked. After a few miles, the car would get a vibration. The brakes would be very soft with the vibration really noticeable in the pedal.

I bought rotors, pads. When I tried to put them on both sides the piston would not go in. Got new calipers. Install went great.
You know the rest of the story
Click to expand...

That verified the brake master cyl push rod, the longer you drive the vibration is coming from the heat, the pads are clamped on the rotors, the soft pedal is coming from the fluid boiling in the caliper. leave the brake hoses alone and work on the pedal push rod, and the master push rod.
 
brian6pac said:
That verified the brake master cyl push rod, the longer you drive the vibration is coming from the heat, the pads are clamped on the rotors, the soft pedal is coming from the fluid boiling in the caliper. leave the brake hoses alone and work on the pedal push rod, and the master push rod.[/QU

Are the pushrods known to just go bad?
Click to expand...
 
No but if you read what he wrote he bought the car and that was the problem, then he changed the pads calipers and rotors to try to fix the problem. #8 & #9 read it
 
67Dart273 said:
A VERY common cause of this is mismatched parts at the master cylinder, causing the master piston to "not return" fully. This does not uncover the ports in the top of the bores of the master, causing pressure to be held

A quick way is to pump up the brakes, and with one wheel jacked up, if it is obviously dragging, take a rag/ container, and crack the nuts at the master........see if there is fluid released, and if the tire then frees up
Click to expand...
That reminds me of what I just went through with my boat trailer brakes, except my issue was my own stupid fault . I had just finished packing the wheel bearings and replacing the wheel cylinders and shoes, and decided to go ahead and get new tires too. I was just about to disconnect the trailer from the truck and grab some lunch while they were replacing the tires when the shop manager told me they could have the new tires balanced and mounted in 15 minutes, so I decided to just wait. I still wanted to disconnect the trailer to avoid damage to the surge brake master cylinder from jacking the trailer up, but I let them convince me that they could jack up both sides simultaneously and maintain even pressure on the coupler--big mistake! I drove about 7 miles back home, and smelled frying brake shoes and cooked wheel bearing grease as soon as I got out of the truck. I disconnected the trailer, jacked up one side, and actuated the master cylinder by hand. Sure enough, when I released it, the brakes remained locked up. I cracked the line open at the master cylinder and the brakes released. The actuator had gotten damaged when they jacked up the trailer, and was sticking. I replaced the whole coupler, including master cylinder and actuator with shock absorber, and after repacking the bearings with fresh grease, everything was fine.
p.s. All brake parts and new coupler from etrailer.com--great products, great prices, and great customer service! (No, I have no affiliation with them, and this is not a paid endorsement!)
 
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