How much brake fluid to add to reservoir; where is fill line?

U might have gotten some air into the line and the lines need to be bled. The fact that you did not add the exact same kind of brake fluid should not be cause for sponginess.

you have a leak brakes are a sealed hydraulic system so when no fluid some part is leaking look under vehicles for fluid also when you fill an empty reservoir you add air also but look for leak

Bleeding the Brake System
When any part of the hydraulic system has been disconnected for repair or
replacement, air may get into the lines and cause spongy pedal action (because
air can be compressed and brake fluid cannot). To correct this condition, it is
necessary to bleed the hydraulic system so to be sure all air is purged.

When bleeding the brake system, bleed one brake cylinder at a time, beginning
at the cylinder with the longest hydraulic line (farthest from the master
cylinder) first. ALWAYS Keep the master cylinder reservoir filled with brake
fluid during the bleeding operation. Never use brake fluid that has been drained
from the hydraulic system, no matter how clean it is.

The primary and secondary hydraulic brake systems are separate and are bled
independently. During the bleeding operation, do not allow the reservoir to run
dry. Keep the master cylinder reservoir filled with brake fluid.

1. Clean all dirt from around the master cylinder fill cap, remove the cap and
   fill the master cylinder with brake fluid until the level is within 1/4 I n.
   (6mm) of the top edge of the reservoir.
   
2. Clean the bleeder screws at all 4 wheels. The bleeder screws are located on
   the top of the brake calipers.
   
3. Attach a length of rubber hose over the bleeder screw and place the other
   end of the hose in a glass jar, submerged in brake fluid.
   
4. Starting at the right rear proceed in this order left front, left rear and
   right front.
   
5. Open the bleeder screw 1/2 - 3/4 turn. Have an assistant slowly depress the
   brake pedal.
   
6. Close the bleeder screw and tell your assistant to allow the brake pedal to
   return slowly. Continue this process to purge all air from the system.
   
7. When bubbles cease to appear at the end of the bleeder hose, close the
   bleeder screw and remove the hose.
   
8. Check the master cylinder fluid level and add fluid accordingly. Do this
   after bleeding each wheel.
   
9. Fill the master cylinder reservoir to the proper level.

Open the master cylinder and fill it to the top ... simple. Use the kikd specified on the cap.

CLUTCH AND MASTER CYLINDER SHARE THE SAME RESERVOIR YOU CHECK LEVEL IN THE MASTER CYLINDER.ADD BRAKE FLUID TO THE MAX LINE DONT OVER FILL.IF MASTER CYLINDER RESERVOIR IS EMPTY.CHECK FOR FLUID LEAKS AT CLUTCH LINES AND CONNECTIONS AT CLUTCH RELEASE CYLINDER AND CHECK BRAKE LINES - CALIPERS - WHEEL CYLINDERS AND BRAKE BOOSTER.FIX LEAKS AND BLEED BRAKE AND CLUTCH SYSTEM.

Here is the procedure from the service manual. I would add just one thing. Do each wheel in this order

1. right rear wheel
2. left rear wheel
3. right front wheel
4. left front wheel

BLEEDING

HINT: If any work is done on the brake system or if air in the brake lines is suspected, bleed the air from the system.

NOTICE: Do not let brake fluid remain on a painted surface. Wash it off immediately.


a)FILL BRAKE RESERVOIR WITH BRAKE FLUID Fluid:SAE J1703 or FMVSS No. 116 DOT3

b)BLEED MASTER CYLINDER HINT: If the master cylinder has been disassembled or if the reservoir becomes empty, bleed the air from the master cylinder.

c)Disconnect the brake lines from the master cylinder. SST 09023-00100 Slowly depress the brake pedal and hold it.

Block off the outlet plug with your finger and release the brake pedal.
Repeat (b) and (c) 3 or 4 times.


BLEED BRAKE LINE

1. Connect the vinyl tube to the caliper or wheel cylinder bleeder plug.
2. Depress the brake pedal several times, then loosen the bleeder plug with the pedal held down.
3. At the point when fluid stops coming out, tighten the bleeder plug, then release the brake pedal. Torque: (Bleeder plug) Front brake caliper
: 8.3 Nm (85 kgf-cm, 74 inch lbs.) Rear wheel cylinder: 8.5 Nm (87 kgf-cm, 75 inch lbs.)
4. Repeat (b) and (c) until all the air in the fluid has been bled out.
5. Repeat the above procedure to bleed the air out of the brake line for each wheel.

CHECK FLUID LEVEL IN RESERVOIR Check the fluid level and add fluid if necessary. Fluid: SAE J1703 or FMVSS No. 116 DOT3

It will be under the hood, on the driver's side, mounted on the brake booster, mounted on firewall. The master cylinder is usually silver with a plastic reservoir on top with a black plasic cap, there should be 4 steel lines coming out of it. Remove the cap and fill up to the "FULL" level on the reservoir.

1. Place a clean shop cloth beneath the brake master cylinder to prevent brake fluid spills.
2. With the ignition OFF and the brakes cool, apply the brakes 3-5 times, or until the brake pedal effort increases significantly, in order to deplete the brake booster power reserve.

Fill the brake master cylinder reservoir with DOT-3 brake fluid from a clean, sealed brake fluid container. Ensure that the brake master cylinder reservoir remains at least half-full during this bleeding procedure. Add fluid as needed to maintain the proper level. Clean the outside of the reservoir on and around the reservoir cap prior to removing the cap and diaphragm.

1. Install a proper box-end wrench onto the RIGHT REAR wheel hydraulic circuit bleeder valve.
2. Install a transparent hose over the end of the bleeder valve.
3. Submerge the open end of the transparent hose into a transparent container partially filled DOT-3 brake fluid from a clean, sealed brake fluid container.
4. Have an assistant slowly depress the brake pedal fully and maintain steady pressure on the pedal.
5. Loosen the bleeder valve to purge air from the wheel hydraulic circuit.
6. Tighten the bleeder valve, then have the assistant slowly release the brake pedal.
7. Wait 15 seconds, then repeat these steps until all air is purged from the same wheel hydraulic circuit.
8. Repeat this procedure with the LEFT FRONT, then LEFT REAR and finally the RIGHT FRONT.
9. Fill the brake master cylinder reservoir to the maximum-fill level with DOT-3 brake fluid from a clean, sealed brake fluid container.
10. Slowly depress and release the brake pedal. Observe the feel of the brake pedal.
    

You need to do more than just adding fluid. There must be a leak some where in the brake lines. You need to fix that than add fliud and bleed all the brakes. If you don't your brakes won't work right.

Yes. Add fluid to the reservoir and watch/ look around for any leakage but I doubt.

Take care and rate this.