front brakes constantly sticking on 70 B body?

Posted By: JRs_Charger

front brakes constantly sticking on 70 B body? - 02/21/10 04:01 AM

Okay, the short version is, I have a 70 Charger with the original disc brakes up front.

The calipers are the original single piston style, and the rear brakes are the original drums. It was a factory power disc car, but someone has removed the brake booster and fitted a master cylinder from a 71-74 E body.

All the lines, calipers, and master cylinder all have less than a thousand miles on them. They are a few years old however, except for the master cylinder, it's new.

My problem is the front brakes drag constantly. Almost to the point where the left wheel cant be turned by hand once the car is jacked up. The right front isn't as noticeable, but it drags too.

Any ideas whats going on here? Aside from the deleted brake booster and the master cylinder from an E body, the rest of the brakes are as they were originally.

Any ideas where i should start looking?

I would appreciate any help, thanks!

Posted By: DAYCLONA

Re: front brakes constantly sticking on 70 B body? - 02/21/10 04:36 AM

As long as the master is a disk/drum unit it shouldn't matter in your application, unless your concern is originality,....seeing that your car was "converted" to manual disk, perhaps the swap isn't correct, linkage wise?,...sounds like residual pressure from the master is present,....are you able to pull the brake pedal up from it's current resting position?, if it's already against the frame stop, try disconnecting the pedal linkage, and jack the offending tire(s) off the ground and attempt turning,....BTW is the pedal push rod an adjustable threaded manual unit?

You got to do a little "diggin" and supply some more info

Mike

Posted By: RapidRobert

Re: front brakes constantly sticking on 70 B body? - 02/21/10 04:36 AM

Quote:

Any ideas where i should start looking?

Take off the line at the M/C port closest to the firewall and stick a drill bit deep into the brass seat and see if you feel the springy RPV & if so pull the brass seat out w a screw & remove it or get the right M/C which will let you select the best bore size assuming that your current bore size is not ideal. Good there? might need to replace the calipers and hoses can collapse but k.i.s.s. and since both sides are having a problem I'd start w the M/C. EDIT (1st) What Dayclona said disconnect the horizontle pushrod from the pedal so the M/C piston is retracted

Posted By: Hemiruss

Re: front brakes constantly sticking on 70 B body? - 02/21/10 04:40 AM

Well I just jacked my up and the last owner had the same problem,he changed all the front calipers,mount bolts,and turned rotors.Still does it and my other Bee from the 70's did it also.I'm in the process of getting the m/c and booster done,but I've heard this may not help...I'll keep you posted.I've not removed the calipers and checked the slide area of the mounts.
Also I've been wanting to replace the hoses as they will "flap over"and hold pressure and give you the same result.So jack it up,hit the brakes and get it to act up,then crack the bleeders loose and see if that helps,it could be the hoses..

Just my.

Posted By: 68HemiB

Re: front brakes constantly sticking on 70 B body? - 02/21/10 06:50 AM

I second the recommendation to crack the bleeder on the offending wheel when you find it dragging.

That will at least isolate it between something that is holding pressure in the system [if cracking the bleeder releases the brakes] versus a mechanical hangup of the piston, sliders, etc [if cracking the bleeder has no effect].

Posted By: macmic87

Re: front brakes constantly sticking on 70 B body? - 02/21/10 01:53 PM

my friends went through this situation last summer. it ended up being the proportion valve. now you say it is original and theirs was not, but there was a problem internally with a washer that was not of the right shape that let it act as a check valve and would hold the brakes (this problem was addmitteed to by the vendors at carlisle last summer). also here is a thread that may help to diagnose.

https://board.moparts.org/ubbthreads/show...;gonew=1#UNREAD

Posted By: 440challenger

Re: front brakes constantly sticking on 70 B body? - 02/21/10 02:00 PM

are the calipers just sticking? did you try tapping them with a dead blow and see if the wheel turns free? Maybe the bores are corroded. and you just new to clean them up?

Posted By: IronWolf

Re: front brakes constantly sticking on 70 B body? - 02/21/10 02:52 PM

I fixed my sticky caliper by replacing the front brake hoses ('72 'cuda ) How old are your hoses ? HTH.

Posted By: ThermoQuad

Re: front brakes constantly sticking on 70 B body? - 02/21/10 09:06 PM

Be sure the calipers can travel on the pins. Remove the rotor,put the caliper back on and see if it slides the pins.

Posted By: Lefty

Re: front brakes constantly sticking on 70 B body? - 02/21/10 09:21 PM

Quote:

My problem is the front brakes drag constantly

In my experience that's usually caused by there not being a gap between the brake pedal rod and piston in the MC or booster to MC interface.

Posted By: JRs_Charger

Re: front brakes constantly sticking on 70 B body? - 02/23/10 04:43 AM

Well, I finally had a few minutes to spend on it. I didn't get to check the proportioning valve, or the master cylinder, however I did notice a couple of things.

First off, cracking the brake bleeder showed that there was no line pressure on it. So I assume that the master cyl isn't sticking open now?

When I put a c clamp on the caliper piston to compress it, there was alot of resistance. It was a major pain to get the piston to go back in the bore. This was more prevalent in the left caliper than the right.

I bought the calipers as remans in 04, and the car has sat alot since. So Is it possible that these things are corroded on the inside maybe? Or something else I'm missing?

The brake lines have less than 5000 miles on them, as does the 1 year old master cylinder. The proporting valve is the original and who knows what's going on inside it, i havent pulled it yet.

Thanks again for the help guys, I appreciate it!

Posted By: RapidRobert

Re: front brakes constantly sticking on 70 B body? - 02/23/10 06:32 AM

Quote:

First off, cracking the brake bleeder showed that there was no line pressure on it. So I assume that the master cyl isn't sticking open now?

yes if you are checking the bleeders after pumping the pedal. I'm thinking calipers now.

Posted By: donbarnes

Re: front brakes constantly sticking on 70 B body? - 02/23/10 03:55 PM

My 95 Nissan P/U was dragging the front brakes recently, smelled like a semi going down the road. I pulled the calipers apart and the pistons had rust/crud between the area of the seal and the dust seal. They looked like some kind of hard chrome and cleaned right up on the buffing wheel- put them back together after that and they work perfectly again

Posted By: john55

Re: front brakes constantly sticking on 70 B body? - 02/23/10 05:29 PM

yes if you are checking the bleeders after pumping the pedal. I'm thinking calipers now.

sounds like a stuck piston