86 diplomat front brakes dragging

[SuicideRider]

My dippy, betty lou is giving me a problem. Front brakes are dragging severely. At first start up, all is good.but within 4-5 miles of in town driving they start dragging. Last year the right front did this, so I figured the hose is bad and bought one.( had about 100,000 miles at time) pulled the wheel, hose looks practically new. But the pads were shot, changed pads and all was good. 13 months and 7800 miles later the problem is back and worse than ever. Feels like both fronts. I know it's not the rears, they dont work at all. (Found that out late last winter hung up on ice)
Just had knee surgery and still recovering. So I'm not to mobile yet and not keen on getting it infected again.
Where do the gurus here think I should investigate first. Master, calipers,etc. And could the anti rattle hardware affect this? Cause the are noisy. Thanks

 

[Aspen500]

I'd start by first checking the calipers. See if the pistons press back into the caliper without a ton of force. Use a c-clamp for this. If OK, drive the car until they are dragging bad and then, back home, crack a bleeder screw and see if there's pressure and if the brake releases. If there is pressure being held, next try cracking the line at the master (will be the rear fitting) and recheck for dragging. Could be a the hoses but it's rare that BOTH would have a problem and you say they look new. One other check is, once the brakes are dragging, loosen the master cylinder nuts and pull the master forward slightly and then see if the brakes release. If they do, the pushrod in the booster is too long and holding the pistons where the compensation ports are blocked and the fluid can't return to the reservoir. If something is blocking the return fluid flow, the farther you drive, the hotter the brakes get, which makes the fluid expand and apply the brakes even more, which makes the fluid expand even more and,,,,,,,,,,,,,well, you get the idea. Now, if the problem is restricted return flow, pushing the pistons back in the caliper will also be tough (which can falsely condemn the caliper)unless the bleeder is open.

Anyways, those are some possible causes of dragging disc brakes.

 

[Ele115]

If those calipers have the plastic pistons, they will get distorted and swell causing them to bind and not release. The cure is to rebuild them with stainless pistons.

 

[Mikes5thAve]

Start by pushing them back in.and see what happens. Also make sure the calipers and brackets are clean and not hanging up on anything. It's not very likely to be anything with the master cylinder push rod unless it's been off before.
What's wrong with the back brakes? It could be something with that causing problems with the proportioning valve.

 

[SuicideRider]

Not sure yet. Assuming just shoes and adjustment. Health has been limiting my work on her. Doesn't loose fluid so wheel cylinders are good

 

[SuicideRider]

Did not know about the plastic caliper pistons. Cant remember if I even looked at pistons. Will definitely check that out.

 

[Aspen500]

I only mention the master pushrod because I have run into vehicles where the pushrod "got longer" by itself and caused the brakes to drag a half dozen times over the past 35 years at work. It's rare but it does happen. This is on cars that have never been apart. My theory is, something in the booster gets bent or warped over the years of use and essentially makes the pushrod longer in relation to the master cylinder piston. A new booster fixed each of them. As I said though, it's very rare.

 

[SuicideRider]

I only mention the master pushrod because I have run into vehicles where the pushrod "got longer" by itself and caused the brakes to drag a half dozen times over the past 35 years at work. It's rare but it does happen. This is on cars that have never been apart. My theory is, something in the booster gets bent or warped over the years of use and essentially makes the pushrod longer in relation to the master cylinder piston. A new booster fixed each of them. As I said though, it's very rare.

Now that is interesting. I never would have thought about that. To my knowledge my girl hasn't been apart .
Thank you so much Aspen500. Its something I'll definitely investigate

 

[GregG48213]

brakes are dragging

I had an R-body back in the day, and it had a leaky power brake booster (rust holes). This would gradually cause the brakes to apply.

 

[Mikes5thAve]

I only mention the master pushrod because I have run into vehicles where the pushrod "got longer" by itself and caused the brakes to drag a half dozen times over the past 35 years at work. It's rare but it does happen. This is on cars that have never been apart. My theory is, something in the booster gets bent or warped over the years of use and essentially makes the pushrod longer in relation to the master cylinder piston. A new booster fixed each of them. As I said though, it's very rare.

Strange. I'd agree on your guess.
I converted one of my cars to a dual master cylinder last fall and had to deal with push rod length.

On what they said above I wonder if it could be a booster problem. Since it starts off fine and then starts happening maybe it does have a vacuum leak that's somehow holding the brakes a bit and when it sits not running its slowing bleeding off that vacuum.

 

[SuicideRider]

Strange. I'd agree on your guess.
I converted one of my cars to a dual master cylinder last fall and had to deal with push rod length.

On what they said above I wonder if it could be a booster problem. Since it starts off fine and then starts happening maybe it does have a vacuum leak that's somehow holding the brakes a bit and when it sits not running its slowing bleeding off that vacuum.

I appreciate you guy's thoughts on this. My inner voice was wondering about the booster, but couldn't really see it doing that. My past vehicles that had booster issues was always vacuum leak causing stiff pedal. Now I have some diagnostic procedures to follow. Thank yall.
I'll update the cause and fix.

 

[AJ/FormS]

Cause the are noisy.

Caliper rattle is a good sign; it means nothing is seized,lol.

 

[SuicideRider]

Actually got to work on her today. Caliper is frozen. So I just ordered calipers and hoses for both sides. That caliper is so stiff that I twisted the c-clamp trying to push piston back in.

 

[SuicideRider]

Update: replaced calipers and hoses on both sides. Just got back from test drive. All is good. Had to replace fuel pump in the middle of this.
Just wanted to thank yall for the helpful responses. Betty lou and I appreciate it.