1988 Volvo 740 - renewed brake pads all around, new discs on front. Brake light is still on. Brakes seemed to seize for a short time, then released. Is this a problem with the ABS unit?, can I service this unit?

There are a number of issues that can cause overheating disc brakes. Disc brakes, when released, separate from the disc by the action of the rotor moving between them (since no rotor is perfectly true, there is a small about of wobble and it pushes the pads away from the rotor surface). Things that can cause this to go wrong are:

1. Caliper pistons that have rust rings that cause sticking. This most often will happen right after or shortly after replacing old, work out pads with new ones. Because the caliper piston was extended out farther with the worn pads, its surface may get rusty. This rust can cause sticking when the piston is pushed back into the bore with the new, thicker pads.
2. Caliper slide bolts will rust and get sticky, not allowing the caliper to release properly and re-center itself on the rotor. What you often see here is that one pad (inner or outer) is totally worn out and the other seems normal.
3. Rusty brake lines/caliper internals can cause restrictions in the flow of brake fluid and hold pressure after the brake pedal is released.

It is highly recommended that whenever you change your brake pads, you replace the caliper slide bolts use a new brake hardware kit when reinstalling. The additional cost is almost always saved in longer brake pad life, and fewer complications.

If your brake hose collapsed internally that will cause brakes to lock to be sure its the hose and not the calipers open the bleed screw and see if the rotor release. If they stay locked then maybe calipers seized try to pry brake pads apart with caliper mounted and brake bleeder open if they return easy then change your brake hose.

Do you live in a rusty climate? You don't say what car or if it's front or back, but rusty parking brakes that don't release is a common problem. Also, brake lines CAN have a little pinch/break in them that make them act like a valve and you step on the brake and push fluid down, but then the 'valve' closes and the fluid can't be released back and release the brakes leading them to grab/overheat.

Because of the brakes locked on you could try having a few friends rock the car backwards and forwards making sure the handbrake is off and and gear lever in neutral , otherwise you will have to remove the wheels,1 at a time, and making sure the handbrake linkage is released hit the brake drum with a good hammer around the outside edge, till the drum can be levered off, if you have Disc's at the front, its best to remove the Caliber by undoing the retaining bolts, After so long you will have to renew most of the braking system,ie new rear shoe's and brake cylinders, at the front New pads and new Disc's rebuild the Calipers with new pistons and seal's,
good luck.

The brake hose is clogged. When under pressure from applying breaks, the piston is forced tight to the rotor. When released the fluid will not return through the hose because there is no real pressure. Replace the hose.
murf427

Have the rotor turned down or replaced, and have that calipar checked, it might be seized up.

this estimate seems very high,even if he is using OE parts,labor for this job is approx 100 dollars

As a rule of thumb to any brake system operating properly the most important is cleanliness of it's hydraulic brake fluid. If your system has moisture in your brake fluid it will cause rust where metal or even rubber are present. Incorrect brake pads would also effect operation such as seizing. Applying a small amount of white grease to the bake pad sliders would help the movement of the pads freely along the sliding perch. A contaminated fluid will cause it to heat up faster and may cause seizure from rust settling at the pistons inside the caliper. If you never service a brake system I would strongly advice you let a certified technician look at your brake problem. Brakes are a safety feature which guessing is not part of a solution. This involves the safety of your lives. Use only premium replacement parts avoiding failure. Your lives are most valuable and when using inferior you also get inferior safety.

You may have contaminated brake fluid. The fluid gets too hot, caused the fluid to expand and lock up your brakes. once it cools it will allow you to move. Flush the brake system, start at the wheel farthest from the master cylinder and bleed the system until all the old dirty fluid is out. Just allow it to gravity bleed, don't waste your time doing the pump and release method. It only gives your buddy a sore foot and if you miscue you **** air back into the line.

Let me know if I can help you with any more info or guidance.

There is a tool available from most auto parts supply outlets, it is a plate that has a compression bolt through it, you slide the plate into the caliper, and tighten the bolt against the piston, then keep turning until the piston is all the way in. These are relatively inexpensive and good to have for next time.

hope this helps.
Ed