88 t-bird non abs. the front brakes drag. i have replaced all rubber lines also new master cyl. new front brake calipers. rear brake hose preasure will bleed of after it has set for 15 to 20 min.can someone tell me why preasure is not beeing released.

Its possible that your rubber lines are collapsed. I've had them keep fluid from going thru as well as not releasing pressure. See if fluid gets to caliper thru rubber. You can plug it with your finger and release pedal. If you feel vacuum and fluid flows well when you push brake, that's probably not the problem. Its somewhere to start tho.

what is the year ,make and model.? does it have abs brakes

First, try bleeding the longest brakeline first, then next longest, and so on.

You can try troubleshooting several ways. Here are some possibilities: Front rubber brake hoses collapsed internally.(There is 1 way pressure to calipers, Gravity return) Master cylinder, sticking Calipers, ABS valving.

A diligent mechanic would attach a pressure gauge on the Brakelines to isolate the problem. If the pressure did not return to Zero after the Brake pedal was released, the individual component can be identified and replaced.

The cost to run the tests is compared to Labor to replace the bad part. With testing you only buy the part you need. You pay a third party to replace the single bad part versus guesstimates and doing it yourself.

Front end rubber brake hoses, cheapest, then Master cylinder or single Caliper. But if replacing both Calipers, they combine to cost more than a Master cylinder. ABS unit $$$

Labor versus parts. Some of the parts may be needed with guesstimates so difference really is buying something you don't need YET. You can look at it a preventative maintenence.

Brake specialty shops. Can do testing. Some offer lifetime Warranties on parts. Quick You have already installed pads. Repair place may not guaranty without replacing your new pads.

I hope my solution is helpful, please rate.

Check the rear wheel cylinders? Was anything leaking at the master cylinder? Does it have ABS?
Check the front caliper slides are free. Check the front caliper pistons for leaks as well. This is all assuming you bled the brakes(all 4 wheels) properly after all that replacement! You're getting air from somewhere for sure or if it has ABS, the pump may have a problem.

The brake system bleeding procedure differs for ABS and non-ABS vehicles. The following procedure pertains only to non-ABS vehicles. For details on bleeding ABS equipped vehicles, refer to the ABS procedures later in this section.

WARNING Make sure the master cylinder contains clean DOT 3 brake fluid at all times during the procedure.

1. The master cylinder must be bled first if it is suspected of containing air. Bleed the master cylinder as follows:
   1. Position a container under the master cylinder to catch the brake fluid.
   2. Loosen the left front brake line (front upper port) at the master cylinder and allow the fluid to flow from the front port.
   3. Connect the line and tighten to 24 ft. lbs. (32 Nm).
   4. Have an assistant depress the brake pedal slowly one time and hold it down, while you loosen the front line to expel air from the master cylinder. Tighten the line, then release the brake pedal. Repeat until all air is removed from the master cylinder.
   5. Tighten the brake line to 24 ft. lbs. (32 Nm) when finished.
   6. Repeat these steps for the right front brake line (rear upper port) at the master cylinder.
      

WARNING Do not allow brake fluid to spill on or come in contact with the vehicle' finish, as it will remove the paint. In case of a spill, immediately flush the area with water.

1. If a single line or fitting was the only hydraulic line disconnected, then only the caliper(s) or wheel cylinder(s) affected by that line must be bled. If the master cylinder required bleeding, then all calipers and wheel cylinders must be bled in the proper sequence:
   1. Right rear
   2. Left front
   3. Left rear
   4. Right front
2. Bleed the individual calipers or wheel cylinders as follows:
   1. Place a suitable wrench over the bleeder screw and attach a clear plastic hose over the screw end.
   2. Submerge the other end in a transparent container of brake fluid.
   3. Loosen the bleed screw, then have an assistant apply the brake pedal slowly and hold it down. Close the bleed screw, then release the brake pedal. Repeat the sequence until all air is expelled from the caliper or cylinder.
   4. When finished, tighten the bleed screw to 97 inch lbs. (11 Nm) for the front, or 66 inch lbs. (7.5 Nm) for the rear.
3. Check the pedal for a hard feeling with the engine not running. If the pedal is soft, repeat the bleeding procedure until a firm pedal is obtained.

Fig. 1: Loosen the front brake line in order to bleed the master cylinder

Fig. 2: Connect a bleed hose from the bleed valve on the front caliper to a jar of brake fluid

Fig. 3: Always follow the lettered sequence when bleeding the hydraulic brake system

Hope this helps to solve it; remember to rate this answer.

Have you changed the brake hoses on the front going to the brake caliper?If not,this could be the problem,also,when bleeding,only pump the pedal one time upon releasing the bleeder screw,do not pump the pedal,start at the master cylinder,then the right rear,and the left rear,and the right front and left front in that order,adjust the rear brakes to where the brakes are dragging pretty good,but are not locking up,

When you said, the bleed valve had to be loosed before the caliper would release, (caliper is already replaced), then we know there was a lot of preasure in the braking lines backed up some where,
and every time the brakes are applied to compress the the caliper to stop your truck,
the preasure would not release,
This
Is a clear indication that the Flexible Rubber Brake Hose attached to the caliper is backed up, clogged, kinked, etc..
That would be the next item in the brake system to check.
Its Bottom Up Disagnostics...
When the hose is off try to slide a strong piece of wire (metal clothes hanger) through the hose..

SOLUTION:
Replace Rubber Brake Line's, on both sides.
I reccomend Stainless Steel Braided Brake Line.

Here is a video that kinda shows corrosion in a rubber hose.
Also check out other videos on youtube.

worn out caliper maybe. is it on one side??? if so may be a bad brake line.

The piston is binding in the wheel brake cylinder, perhaps a bit of rust in the cylinder.
Inspect it, replace wheel brake piston and maybe the cylinder if you can't make it "smooth".

Brake Lines and Hoses
Double-walled steel line is used in the hydraulic lines between the brake master cylinder and the front tube connector, and between the brake master cylinder and the flexible brake hose at the rear wheels.
Double-flared brake lines provide good leak-proof connections.
When replacing hydraulic brake lines, hoses, or connectors, tighten all connections securely. After replacement, bleed the brake system; refer to Section 206-00 .
The wet appearance of the outer cover of the rubber brake hose is referred to as "sweating." This is a normal condition for neoprene rayon braid hose and is not a sign of leakage or cause for replacement of the hose.

Hydraulic Brake System Components — Non-ABS


Item Part Number Description 1 2005 Power Brake Booster 2 2455 Brake Pedal 3 2261 Rear Wheel Cylinder 4 2552 Rear Disc Brake Caliper— (Mexico Only) 5 2B120 Disc Brake Caliper—, Front 6 2B091 Brake Pressure Control Valves 7 2140 Brake Master Cylinder