brake help

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silver fox

silver fox

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I have a 73 duster 340 disc front drums in back the pedal would not return back up also the front disc would not release the wheel after pressing the breaks so I replaced the mc which cleared the pedal return problem so I thought the pin's might be ceased because of non use took the caliper's off pin's were loose & free removed the piston's they look clean rust free
checked to see if the brake switch was clear so the pedal could return it seem's good the mc is correct for the car any other thought's as to why the front will not release the wheel after using the brake if I leave the car sit for a day or so the front's turn on till I use the brake
 
have you verified that your rubber brake lines are not swollen shut internally...while you have pressure to expand from the master to the cylinders..there is nothing but the square O-ring to pull the piston back in the caliper and on the rear only the light return springs..
 
bigaadams said:
have you verified that your rubber brake lines are not swollen shut internally...while you have pressure to expand from the master to the cylinders..there is nothing but the square O-ring to pull the piston back in the caliper and on the rear only the light return springs..
Click to expand...
bigaadams said:
have you verified that your rubber brake lines are not swollen shut internally...while you have pressure to expand from the master to the cylinders..there is nothing but the square O-ring to pull the piston back in the caliper and on the rear only the light return springs..
Click to expand...
I thought I would get new hose but can't see the kind I need on rock auto the one's I have screw into the calliper
 
I agree with the hose idea. Crack the bleeder at the stuck caliper,when it is stuck. If it bursts out with any kind of force, that's a tell.
Adjusting your rear brakes tighter(assuming they are loose) will force fluid to return to the master, pushing the piston assy towards the pedal, and help to park it.

Do you have a brake booster?
There is a spring in there to return the diaphragm, which is connected to the pushrod, which is connected to the pedal.Short of a bad hose,maladjusted rears, or a mechanical pedal problem, I might look here.
 
I looked at rock auto for hose they don't seem to have the one's I have, the one's I have
screw into the calliper
 
Yeah we saw that. Give FABO a little time to solve that one. In the meantime, some pics would help, and if you know any history behind that situation, now's the time to sound off.
 
I concur with the brake hose(s) as the most likely problem. Crack open the bleeder when the brakes are stuck as suggested & observe the fluid flow. If the brakes release & turn freely close the bleeder & go back up the hose to the fitting where the brake line threads into the hose fitting & crack it open there(after applying the brakes to get them to stick again) & see if they release then. Closely watch the amount of fluid that comes out here. If there isn't a good amount of fluid & the brakes don't release quickly then you have a blockage in the hose(s). If the hoses are old or unknown it's probably best to just replace them anyway. But the procedure mentioned will help isolate the problem if it is the hoses.
Also make sure the pushrod is seated correctly in the master cylinder piston & that the M/C is being allowed to fully return to its rested position. This could also cause a similar problem like yours.
Good luck.
 
both front wheel's stick when the brakes are applied fluid shoots when I open bleeders would this be a valve problem what are the odd's of both hose's going
 
I doubt it.
I bet money the C-port is closed
If the pedal is correctly parking at the top, then the pushrod needs to be shorter or perhaps it is not correctly seated in it's receiver at the back of the M/C, as already stated

OOps that's not right. Let me rephrase that;
I bet money the C-port is closed, cuz the pedal is not returning to its parking spot, cuz maybe the pushrod needs to be seated or adjusted.

That still doesn't sound right. Lemme think.

Ok here it is, forget all the above stuff;
For some reason there is pressure remaining in the system, after the pedal is released. You say the pedal is parking now. There are just three possibilities;
1) two bad hoses, or
2) stuck Proportioning valve, EDIT this is false, see post#16
3) somebody put a residual valve in the port to the front brakes.
It could be any of the Three. Yeah so back to post #9, and Lonewolfs method will help you find the issue. I can no longer think about two hoses failing at the same time, and it would be a rare thing that a rebuilder would install an R-valve where it don't belong.
Ima going to throw in with jimt1975rr, post #5
Not to be a smartazz, but the front brake line should begin at the larger reservoir.
 
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I'm going for the valve. now where to find one I see one on summit any other place i can look thank's all
 
Just take yours apart and clean it. Easy-peasy
You will need some Silicon O-ring lube, to get the valve back in.
The body is all brass, consequently it is practically waterproof, and re-useable until the end of the age..
However since moisture settles out in the lowest part of the system, it carries contaminants along with it like ants on parade. The contaminants are tiny particles of iron oxide(rust). Some of them clump together in tight spaces like the P-valve.
The rubber seals on the valve of the safety sw portion,(there to keep the two systems separate) are almost impervious to anything normally found in the brake system. But I have seen them swell up from prolonged contact with oil. I have heard that they are not available. So if yours won't go back in with the silicon lube, or they are obviously swollen, then you may need a new plan.
Your choices are; 1) another used one, or 2)swap it out for a safety switch and an aftermarket stand-alone P-valve, or 3)Y-couple the fronts together, and separately couple the rears together, and again run the stand-alone, or 4) buy a new one.
As to the proportioning side, I don't recall any seal there. It is just a blow off valve, like a regulator. I threw all those parts away, and have no proportioning at all on my rear brakes Cuz it's really really hard to lock up 295s earlier than the 235s up front.Actually make that impossible; the fronts always lock first and hard while the rears mostly just complain.
 
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Stop! Wait.

I made a mistake.
It cannot be the P-valve. There is nothing in there that affects the front brakes. The safety switch cannot come far enough forward to block the front passage, and the proportioning section is the last part on the way to the rear brakes.

I'll say again, it cannot be the Combination valve. We commonly call this valve a Proportioning valve, but it's a throw-back to an earlier time when the valves were all separate.Properly,when the block has both the safety sw and the proportioning section, then it is a Combination valve. Some early DB cars had a metering valve in the front line, plus a safety sw, plus a separate P-valve. But by 73 those were all gone with just the C-valve remaining.

So that just leave two bad hoses, or the residual valve in the wrong port, or back to the blocked compensating port. Ima going back to the Cport idea, although I have no idea how that could be happening.
If the pushrod hadda been too long during the bleeding procedure, it woould have been impossible to bleed it. If the pushrod hadda been too short, the pedal would be hanging down, and a lot of it's travel would be used up just to innitiate a hard pedal, and then it could be very close to the floor.
So, I'm stumped..
The Rvalve is only 8 to 10 psi, so while I don't think it's in there with your description of fluid coming out with force, I guess I would check it'

Hey something just came to me. If you were to pump the pedal up, to lock both front brakes on, and then crack one side, to see the fluid spurt out; and then without touching the brake pedal,go around the other side and crack it, then; no spurt on second side means the pressure is gone, and so this hose is good. Repeat the test starting with the other side. If same result then that hose is also good.
But if both hoses spurt with the one initial pump-up, it still does not prove the hoses are bad.
That leads to test #2. Pump up the brakes again to lock up the fronts. We now know that this will produce at least one spurt. So simply loosen the M/C retaining nuts or screws and move the M/C back about a quarter inch.Go bungee up the brake pedal so it cannot follow the M/C. Now crack a bleeder. No spurt means the C-port has allowed the fluid to return. Repeat at other wheel. No spurt, same thing. But any one spurt means a bad hose there. If Two spurts,it's gotta be two bad hoses.
So at this point, with the M/C hanging there, and lets say zero spurts, we have proven that the C-port was blocked.
Now that just leaves the why of it,and however did you manage to get the system bled?And how do we keep pushing fluid along for the tests?
Hmmmmmmmmmmmmmmmmmmmmm
I think I got that right. Anybody catch me napping?
 
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