Replaced front pads on my 1999 Nissan Sentra. Brake pedal felt low.Had system flushed, bled and rear shoes adjusted. Still have low pedal and spongy feel. Suggestions?

first replace master cylinder the replace rear wheel brake cylinders.. Inspect front pads for non uniform wear, inspect front rotors replace if badly worn or scarred. You are dealing with 23-24 year old parts.

Once you have bled the air from the brake lines,clamp off the front brake hoses carefully.Does the pedal feel better now?
Then the pad /caliper fit is allowing too much play.Is the pedal the same?Then clamp the rear hose and try the pedal.Is it fine with the rear hose clamped?If so we now know the problem is at the rear brakes.One common low pedal rear brake cause is brake shoes that do not fit the drums.Remove the drums and look at the shoes,are they showing contact wear fully or just in the middle of the shoe?Remove a shoe and place it in the drum.Can you rock the shoe against the drum surface?Once drums have been resurfaced,the shoes will not fit fully against the drum allowing the shoe the flex when applying pressure to it and this can easily create a low soft brake pedal. Of course rear brake adjustment must be correct once brake shoe contact is correct.To correct brake shoe contact,have your shoes re arc-ed to fit resurfaced drums or install new drums.Don't overlook brake master cyl /brake pedal push rod adjustment too.

Did you ensure that the master brake cylinder was topped up properly whilst you bled the back brake shoes?

If you did so and the brakes are free of air in the lines, then you still have to adjust the brake shoes to their operating position. Secure vehicle from movement. Jack back wheels of the ground, support with jack stands. Remove the rubber grommets that covers brake adjustment wheels. Turn star wheel adjuster with special adjustment tool or a wide blade screw driver. Lock the wheels with the adjustments, push in brake pedal until you have pressure, back off adjustments until wheel runs freely. you should have plenty of pedal now. Make sure master is at the right level at all times.

If you don't have pedal now then I would suggest you still have air in the brake lines.. If you pump the brakes until you have pressure and the pedal feels spongy , then you still have air in the line somewhere. Bleed until air is removed.

On these old manual brake systems without automatic adjusters you have to set the shoe clearance by turning the adjuster on each shoe out so the shoe is very close to the drum. If there is too much clearance between the shoe and drum the shoe will move as far as it can and never touch the drum, this will make a low or no pedal pressure.

check or adjust brake pedal, check brake booster or replace new one, check pedal return spring and bushing, check all wheel cylinder or replace, check brake shoe or brake pad, check brake fluid or replace,.

loosen of the hand-brake adjustment and press the brake pedal a few times to self adjust the rear brakes.
Re-tighten the handbrake adj last.
Front brake sounds like a seized caliper,If possible remove caliper and clean and lubricate the piston.
This may work but replacement caliper may be the only other solution.Make sure the caliper slides are also clean and lubricated and the brake pads are in good order.(TRY THIS FIRST)
Also new brake shoes can make the pedal feel spongy for a couple of hundred miles until they have been run in.

Did you adjust the rear shoes out? If the rear drum brakes are out of adjustment they will give you a lot of pedal travel. If the pads are worn have no fear of that U-CLIP brake spring, just change one shoe at a time. Take the spring off one side, change the shoe, put the spring back on the post and do the same to the other shoe, no problem.

there is air there somewhere. try manual bleeding the brakes. do the farthest wheel first. if they are calipers all the way around, when you bleed them tap them gently to remove any air that can still be inside the chambers.

robert

Try having the dealer flush and bleed your system. It is very hard to bleed ABS systems yourself and have safe brakes that still work afterward. Bleeding non-ABS brakes yourself is easy not the same for ABS brakes. Valving, sensors and what-not require a tech and the correct equipment in my opinion. You do it wrong and you could ruin your ABS system. Do that and see if they firm up. I replaced my brake shoes/pads at the same time all new everything in back, drums/springs everything and new rotors up front. then I had the chevy dealer flush, refill and bleed system. Stiffer pedal and brakes work better. Keep in mind the brakes on 99 Tahoes are inaedequate, require new rotors often, heat up and fade/glaze pads regularly. I replace my pads long before they wear down because they glaze up and start fading early. I'll rough em up once maybe, next time, new ones. Every two brake jobs, new rotors for me. Just how it is. They will stiffen a bit and work better but they will never be awesome brakes. Just how it is on 99 and earlier Tahoes. Hope it helps. Very important to bleed correctly though. I'll bleed my 83 Toyota 4x4 myself but not the Tahoe.

You can adjust the shoes outward on the rear by removing the wheels and drums, then above the axle but below the wheel cylinder you will see an arm that is horizontal, pushing both of the shoes outwards. There should be an adjustment nut that you can turn to extend the arm to push the shoes out.