My 92 previa 1.front disc brake sliding pins is lock,is it are big problem. 2.

No.
1. But if the inner and outer brake pads have been installed incorrectly (such as being reversed) the brakes will lock up.

2. If the caliper is bad and the pistons will not retract back into the caliper when the brake pressure is released the pads will lock onto the brake rotor.

3. If the caliper is frozen on the slide pins due to poor and incorrect lubrication of the slides you will also have a problem with brake lock up.

stop and do not drive, get a brake man, in the loop, danger !


this is cause by the MC, the master cylinder, no ABS in 92
not replacing relic calipers in pairs is dumb, sorry risking life and limb using old 20 year old calipers is not bright. a fact, not opinion.
are both caliper locking, at ONCE?
that is the key question .
reasons. (answer for BOTH clipers locking at once)
1: bad calipers ,no piston lasts for 21 years, ever. (relic)
2: the MC piston is not retraced,

#2 is caused for 2 or 3 reasons,,,,
2a; brake pedal adjusted such that the factory play behind piston rod is not zero or minus, causing the MC to lock hydraulically.
2b; the booster was changed and the PP mechanic (weak) did not
RTM , they did not adjust the new booster, calibration ring stated in the FSM.
3: if one caliper (good) locks the rubber flex line is breaking down
inside and is clogged. 21 year old lines are not good to trust.
not life and limb or mine when you hit me...
that too, is fact.

the guide pins must be free, and antisieze lubed or with special
99cent OTC brake grease (very high temp rated,) ask.
the pistons rust. DOT3/4 is hygroscopic and will rust in 21 years.
not a guess. fact.
One other point, 21 year old caliper seals will no longer have
stiction, they fail to retract the piston and the pad drag. wasting fuel and pads. new seals. better, newly rebuilt Raybestos calipers
will make them safe.
fixing brakes in a serial fashion is asking for trouble.
do not cheap out on brakes.

Check this REMOVAL & INSTALLATION
(see Figures 1, 2 and 3 / click over images for zoom )

CAUTION Older brake pads or shoes may contain asbestos, which has been determined to be cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.

1. Remove 1 / 2 of the brake fluid from the master cylinder reservoir.
   
2. Raise and safely support the vehicle.
   
3. Remove the wheels.
   
4. Remove the cotter pin and guide pin.
   

Fig. 1: Rear disc brake components

1. Remove the caliper locating pin cover and remove the locating pin.
   
2. Swing the rear disc brake caliper away from the brake rotor and anchor plate. There is no need to remove the parking brake cable or brake hose.
   
3. Remove the inner and outer disc brake pads.

To install:

1. If installing new disc brake pads, use rear caliper piston adjuster T87P-2588-A or similar tool, to rotate the rear disc brake piston clockwise, retracting the caliper piston. This will allow room for the new brake pads.

Fig. 2: Removing the parking brake cable

Fig. 3: Use the adjuster tool to rotate the piston into the caliper

1. Install the inner and outer disc brake pads.
   
2. Swing the rear disc brake caliper back into position over the disc brake pads.
   
3. Clean the locating pin threads and apply 1 drop of a thread locking agent or similar sealer.
   
4. Apply a small amount of disc brake caliper slide grease to the shaft of the locating pin.
   
5. Reinstall the locating pin and torque to 30 ft. lbs. (41 Nm).
   
6. Reinstall the guide pin and the cotter pin.
   
7. Adjust the parking brake by operating the parking brake control several times.
   
8. Reinstall the wheel and tire assembly. Torque the lug nuts to 62 ft. lbs. (85 Nm).
   
9. Lower the vehicle.
   
10. Adjust the parking brake by operating the parking brake control several times.
    
11. Pump the brake pedal several times to achieve a good pedal before attempting to move the vehicle.
    
12. Check the brake fluid level in the master cylinder fluid reservoir and add fluid as necessary.
    
13. Road test the vehicle and check for proper brake system operation.

Hope this helps (remember to rate and comment this answer).

Brake Pads Removal & Installation Front

To Remove:

1. Drain brake fluid to ½ full level in reservoir.
2. Remove the front wheels.
   
   
3. Remove the front brake caliper assembly.
4. Remove the 2 anti-squeal shims from each of the 2 brake pads.
5. Remove the wear indicator from each of the 2 brake pads.

To Install:
NOTE: When replacing worn pads, the anti-squeal shims must be replaced together with the pads.

1. Using a large C clamp or equivalent press piston into the caliper.
2. Apply disc brake grease to the inside of each anti-squeal shim.
3. Install the anti-squeal shims on each pad.
4. Install the pad wear indicator clip to the pads.
5. Install the pads with the pad wear indicator plate facing upward.
6. Install the brake caliper with the 2 mounting bolts. Torque the bolts 25 ft-lb (34 Nm).
7. Install the front wheels.
8. Fill the master cylinder with new clean brake fluid.
9. Pump the brake pedal several times to seat the brake pads.

Rear TMC made rear brake components

TMMK made rear brake components

To Remove:

1. Drain the brake fluid to ½ full level in reservoir.
2. Remove the rear wheels.
3. Remove the caliper slide pins.
4. Remove the caliper slide pin bushings (TMMK made) (Kentucky).
5. Remove the rear brake calipers.
6. Remove the 2 brake pads with the anti-squeal shims.
7. Remove the anti-squeal shims and pad wear indicators from brake pads.

To Install:

1. Using a large C clamp or equivalent press the piston into the caliper.
2. Coat both sides of the outer anti-squeal shim with pad grease.
3. Install anti-squeal shims to each pad.
4. Install wear indicators on the 2 brake pads.
5. Install the caliper slide pin bushings (TMMK made) (Kentucky).
6. Install the rear brake caliper with the slide pins. Torque the slide pins as follows:
   • TMC made (Japan): Torque the caliper slide pin 25 ft-lb (34.3 Nm)
   • TMMK made (Kentucky): Torque the caliper slide pin 34 ft-lb (47 Nm)
7. Fill the master cylinder with new clean brake fluid.
8. Pump the brake pedal several times to seat the brake pads.
9. Install the rear wheels.

Brake Rotor Removal & Installation Front To Remove:

1. Remove the front wheels.
2. Remove the front brake caliper assembly.
3. Remove the front brake pads.
4. Remove the 2 bolts and caliper mounting bracket.
5. Place match marks on the disc and axle hub.
6. Remove the front wheel disc.

To Install:

1. Align the match marks and install the front disc.
2. Install the brake caliper mounting bracket. Torque the bolts 79 ft-lb (107 Nm).
3. Install the brake caliper. Torque the bolts 25 ft-lb (34 Nm).
4. Install new gaskets and connect the brake hose to the caliper with the banjo fitting bolt. Torque the fitting bolt 22 ft-lb (29.4 Nm).
5. Fill the reservoir with brake fluid.
6. Bleed the brake system.
7. Install the front wheel.

Rear To Remove:

1. Remove the rear wheels.
2. Remove the brake caliper assembly.
3. Remove the brake pads.
4. Remove the 2 bolts and the caliper mounting bracket.
5. Place match marks on the disc and axle hub.
6. Remove the rear disc.

To Install:

1. Align the match marks and install the rear disc.
2. Install the rear brake caliper mounting bracket. Torque the bracket bolts as follows:
   • TMC made (Japan): Torque the bracket bolt 46 ft-lb (61.8 Nm)
   • TMMK made (Kentucky): Torque the bracket bolt 34 ft-lb (47 Nm)
3. Install the rear brake caliper with the slide pins. Torque the slide pins as follows:
   • TMC made (Japan): Torque the caliper slide pin 25 ft-lb (34.3 Nm)
   • TMMK made (Kentucky): Torque the caliper slide pin 32 ft-lb (43 Nm)
4. Install new gaskets and connect the brake hose to the caliper with the banjo fitting bolt. Torque the fitting bolt 22 ft-lb (29.4 Nm).
5. Fill the reservoir with brake fluid.
6. Bleed the brake system.
7. Install the rear wheel

First jack up the front end of the truck on both sides and put jack stands under it. Then remove the tires then the brake calipers. Now would be a good time to replace the brake pads also. Some rotors wil then just slide off if you have the kind with the bearing as part of the rotor assembly then you will need to first remove the cotter pin and the dust sleeve then there will be a big nut to undo. now you can slide off the rotor with the bearing be sure to repack the bearings with new grease before installing the new rotors. You will also need to compress the caliper pistons you can do this by opening up your brake fluid lid on the master cylinder and either using big channel locks or whatever is easiest for you.

I believe that the rear discs are warped or the tires are out of round when braking. More likely, the discs. --- The following are the instructions for replacing the front and rear pads for the front/back rotors. 1999-01 Grand Cherokee Front

1. Drain 2?3 of the brake fluid from the front reservoir. Use the bleeder screw at the front outlet port to drain the fluid. If equipped with anti-lock brakes, relieve the system pressure.
2. Raise and safely support the vehicle.
3. Remove the wheels.
4. Insert a small prybar through the caliper opening and pry the caliper (using the outboard brake pad) to bottom the pistons in the caliper bore. NOTE: This will back the brake pads off of the rotor surface to facilitate the removal and installation of the caliper assembly.
   
5. Pry the caliper support spring out of the caliper.
6. Remove both caliper slide pin bushing caps and slide pins.
7. Lift the caliper from the anchor.
8. Using a piece of mechanics wire, support the caliper so there is not tension on the brake hose.
9. Remove the brake pads from the caliper. Fig. 2: Installing the inward brake pad on the front caliper pistons - 1999-01 Grand Cherokee
   To install:
   
10. Position the brake pads onto the caliper.
11. Position the caliper into place on the anchor.
12. Coat the caliper slide pins with silicone grease and torque them to 21-30 ft. lbs. (29-41 Nm). Install the slide pin bushing caps.
13. Install the caliper support spring in the top of the caliper under the anchor; then, install the other end into the lower caliper hole. NOTE: Hold the spring in the caliper hole with your thumb while prying the spring end out and under the anchor.
    
14. Fill the master cylinder with fluid and bleed the brake system.
15. Before driving the vehicle, pump the brakes several times to seat the pads.
16. Install the wheels.

Rear

1. Drain 2?3 of the brake fluid from the front reservoir. Use the bleeder screw at the front outlet port to drain the fluid. If equipped with anti-lock brakes, relieve the system pressure.
2. Raise and safely support the vehicle.
3. Remove the wheels.
4. Insert a small prybar through the caliper opening and pry the caliper (using the outboard brake pad) to bottom the piston in the caliper bore. NOTE: This will back the brake pads off of the rotor surface to facilitate the removal and installation of the caliper assembly.
   
5. Pry the caliper support spring out of the caliper.
6. Remove both caliper slide pin bushing caps and slide pins.
7. Lift the caliper from the anchor.
8. Using a piece of mechanics wire, support the caliper so there is not tension on the brake hose.
9. Remove the brake pads from the caliper. Fig. 3: Installing the inward brake pad on the rear caliper piston - 1999-01 Grand Cherokee
   To install:
   
10. Position the brake pads onto the caliper.
11. Position the caliper into place on the anchor.
12. Coat the caliper slide pins with silicone grease and torque them to 21-30 ft. lbs. (29-41 Nm). Install the slide pin bushing caps.
13. Install the caliper support spring in the top of the caliper under the anchor; then, install the other end into the lower caliper hole. NOTE: Hold the spring in the caliper hole with your thumb while prying the spring end out and under the anchor.
    
14. Fill the master cylinder with fluid and bleed the brake system.
15. Before driving the vehicle, pump the brakes several times to seat the pads.
16. Install the wheels.

Brake Pads
Removal & Installation
Front





3.4L front disc brake assembly









4.0L and 4.7L front disc brake assembly




To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Front wheel
     
   • Clip, 2 caliper pins, the anti-rattle spring then remove the 2 brake pads
     and the 4 anti-squeal shims

To Install:

CAUTION
Only replace brake pads on 1 side of the
vehicle at a time. Failure to use this procedure could cause the caliper pistons
on the opposite side of the vehicle to pop out requiring the reconditioning or
replacement of the brake caliper.

1. Remove a small amount of brake fluid from the master cylinder.
   
2. Install a used brake pad into the caliper and compress the caliper pistons.
   
3. Apply disc brake grease to both sides of the inner anti-squeal shims.
   
4. Install or connect the following:
   
   
   
   • Anti-squeal shims to the new brake pads
     NOTE: When replacing worn pads, the anti-squeal shims must be replaced
     together with the pads.
     
     
   • 2 brake pads
     
   • Anti-rattle spring and the 2 caliper pins
     
   • Clip
     
   • Front wheel
   
   
5. Depress the brake pedal several times to seat the brake pads.
   
6. Check the brake fluid level and top off as needed.

Rear
To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Rear wheel
     
     
     
     
     
     
     
     
     
     
     
   • 2 cylinder slide pins from rear caliper assembly
     
   • Caliper assembly from rear caliper mounting
     
   • 2 brake pads with anti-squeal shims from rear caliper mounting
     
   • 2 anti-squeal shims from each disc brake pads
     
   • Pad wear indicator plate from the inner side disc brake pad
     
   • 4 pad support plates from the rear caliper mounting

To Install:

1. Install or connect the following:
   
   
   
   • 4 pad support plates on the rear caliper mounting
     
   • Pad wear indicator plate on the inside brake pad
     Note: Install the pad wear indicator facing downward.
     
     
   • Anti-squeal shims on each brake pad
     
   • 2 disc brake pads with anti-squeal shims to the caliper assembly
   
   
2. Apply lithium soap base glycol grease to the sliding part of 2 caliper slide
   pins.
   
3. Install or connect the following:
   
   
   
   • Disc brake caliper assembly with 2 caliper slide pins
     
   • Torque to 65 ft-lbs (88 Nm)
     
   • Rear wheel
   
   
4. Depress the brake pedal several times to seat the brake pads.
   
5. Check the brake fluid level and top off as needed.

--- Removal & Installation
Front
To Remove:

1. Before servicing the vehicle, refer to the precautions in the beginning of
   this section.
   
2. Remove or disconnect the following:
   
   
   
   • Front wheel
     
   • Front brake caliper assembly
   
   
3. Make matchmarks on the disc and the axle hub.
   
4. Remove the front disc.

To Install:

1. Align matchmarks and disc onto axle hub.
   
2. Install or connect the following:
   
   
   
   • Front brake caliper assembly with the 2 bolts
     
     
     
     1. Torque to 90 ft-lbs (123 Nm)
     
     
   • Front wheel

Using a C clamp depress the claiper. There a spot right in the middle to do this. Now the fun part hope you have metic hex key set. The 2 caliper guide pins are on the back inside the boots. Which need to be in great condition. Using the metic hex keys some are 7mm or 8mm turn to your right to remove. Rmove the caliper mounting bracket bolts. Fun part #2 removing the disc rotor. Theres parking brake pads or a durm brake system on the inside of the rotor. If the rotor does not slide off. You must remove the rubber gromet on the back of the backing plate. Using a screwdriver or the old brake adjuster tool turn the star wheel to adjust the parking brake in to remove the disc rotor. All brake guides on the calipers & guide pins need to have high temperture brake grease applyed to them. Buy the big bottle for $10 for the front brakes & future use it comes with a bush. Note ** Remove a guide pin take to auto store buy socket to reinstall guide pin/bolt. Why Caliper guide pins 26lbs torque. Caliper mounting bolts 125lb torque

NOTE: After the wheel bearings have been removed or replaced or the front axle has been reassembled be sure to adjust wheel bearing preload. Refer to the Adjustment service procedure below. On the 1989–92 240SX there is just one wheel bearing, pressed into the hub and no adjusting cap. Refer to the exploded views of the Front Axle Hub Assembly. Review the complete service procedure.

1. Raise and support the vehicle safely.
2. Remove the front wheels and the brake caliper assemblies. NOTE: Brake hoses do not need to be disconnected from the brake caliper assemblies. Make sure the brake hoses are secure and do not let caliper assemblies hang unsupported from the vehicle.
   
3. Work off center hub cap by using thin tool. If necessary tap around it with a soft hammer while removing.
4. Pry off cotter pin and take out adjusting cap and wheel bearing lock nut.
5. Remove wheel hub with disc brake rotor from spindle with bearings installed. Remove the outer bearing from the hub.
6. Remove inner bearing and grease seal from hub using long brass drift pin or equivalent.
7. If it is necessary to replace the bearing outer races, drive them out of the hub with a brass drift pin and mallet.
8. Install the outer bearing race with a tool (KV401021S0 special tool number) until it seats in the hub flush. NOTE: Place a large glob of grease into the palm of one hand and push the bearing through it with a sliding motion. The grease must be forced through the side of the bearing and in between each roller. Continue until the grease begins to ooze out the other side through the gaps between the rollers. The bearing must be completely packed with grease.
   
9. Pack each wheel bearing with high temperature wheel bearing grease. Pack hub and hub cap with the recommended wheel bearing grease up to shaded portions. Refer to the illustration.
10. Install the inner bearing and grease seal in the proper position in the hub.
11. Install the wheel hub with disc brake rotor to the spindle.
12. Install the outer wheel bearing, lock washer, wheel bearing lock nut, adjusting cap, cotter pin (always use a new cotter pin and O-ring for installation after adjustment), spread cotter pin then install the O-ring and dust cap.
13. Install the brake caliper assemblies and bleed brakes if necessary. Install the front wheels.

The drivers side bolts can be accessed by pulling out the guage cluster and some of the ductwork. It's a tight fit but can be done. The passenger side on models without the airbag is accessed by going through the glove box. 
You can get to the top of the R Front shock tower bolts (14mm allen x 3) by removing the Airbag and glove box assemblies... there's barely enough room to get to those bolts. the deepest nut is going to be really hard to get out, but prevailed eventually. A time consuming project, but worth while.

As for the break lines: You don't have to take them apart if you try this trick.
First you need to remove the clips that hold the brake lines to the strut supports.

After the clips have been removed there should be enough play in the lines to shift the fittings out of the supports.

I use bolt cutters to make two cuts in the brake line supports about 1/4" apart. Remember to do the same to the new struts.

The brake line should just slide right out. When you put your new struts on the brake lines will slide in the slots you put in.

When you reasseble the brake lines to the supports the clip will hold the fitting tight even with the slot cut into the support.


Good luck and hope this helps.