1) Theory — how the system works and what fails
- Disc brake basics: hydraulic pressure from the master cylinder pushes a piston in the caliper, which forces a friction pad against a rotating steel rotor. Stopping comes from kinetic energy → heat via friction; pads provide the friction and rotors take the heat.
- Floating caliper behavior (used on Toyota 22R front): one piston on the inboard side pushes the inboard pad; the whole caliper slides on guide pins so the outboard pad contacts the rotor. Smooth guide-pin movement and parallel pad contact are required for even wear.
- Common failure modes:
- Pad wear (loss of friction material) → increased stopping distance, audible squeal from wear indicators.
- Pad glazing or contamination (oil/grease) → reduced friction, grabbing or low bite.
- Rotor wear, scoring, thickness loss, or runout → vibration, pulsation, uneven contact.
- Seized piston or sticky guide pins → uneven wear, dragging, overheating.
- Air in hydraulic lines → spongy pedal.
- How replacing pads fixes it:
- Restores proper friction material and thickness, so stopping force at a given hydraulic pressure returns to spec.
- New pads with correct surface, plus rotor attention (resurface/replace), restore full contact area and consistent friction.
- Cleaning/lubricating pins and replacing hardware restores caliper mobility and parallel pad contact so both pads wear evenly and don’t drag.
- Compressing the piston sets clearance appropriate for the new pad thickness so pads re-engage correctly.
- Bleeding (if required) removes air so hydraulic pressure reliably moves the piston.

2) Preparatory checks (why)
- Inspect rotor for thickness, scoring, heat cracking, and runout. If rotor is below minimum thickness or severely scored/warped, it must be resurfaced or replaced. Theory: a thin or warped rotor can’t absorb heat or provide flat contact; new pads on bad rotors will wear fast or vibrate.
- Inspect caliper boots and brake hose for leaks. Seized or leaking components must be addressed; new pads alone won’t fix hydraulic/leak problems.
- Note brake fluid level — compressing pistons pushes fluid back into reservoir.

3) Tools and safety (why)
- Jack, jack stands, wheel chocks: support the car safely — hydraulic jacks can fail.
- C-clamp or piston-spreader, socket set, hex/allen for caliper bolts (floating caliper often uses sliding pin bolts), flat screwdriver or pry tool, wire/cable to hang caliper, brake cleaner, high-temp brake grease, torque wrench.
- Why: safe lifting, correct piston compression, correct torque for hardware to maintain clamp and alignment.

4) Ordered repair procedure with theory (concise)
1. Park on level ground, set parking brake (if rear drums, release for front work), chock rear wheels.
- Theory: prevents vehicle movement.
2. Loosen front wheel lug nuts slightly with car on ground.
- Theory: easier, safer to break lug torque before lifting.
3. Jack up vehicle and secure on jack stands. Remove wheel.
4. Inspect visible components (pads through caliper, rotor condition, brake lines).
- Theory: confirm initial diagnosis and note any extra parts needed.
5. Place a container or rag under caliper and unbolt caliper guide/retaining bolts. Support the caliper on a hanger or wire — do NOT let it hang by the brake hose.
- Theory: keeps hose safe and prevents damage to hydraulic line.
6. Remove old pads, anti-rattle clips, and hardware. Inspect pad backing and wear pattern.
- Theory: wear patterns tell you whether caliper was sliding or piston was seized (inner vs outer wear).
7. If replacing or resurfacing rotor: remove caliper bracket (if needed) and remove rotor. If rotor stuck, use penetrating fluid or bolts to pull it. Measure rotor thickness and runout.
- Theory: correct rotor surface ensures full-pad contact and prevents vibration; thickness ensures heat capacity and safety.
8. Clean rotor surface or install new rotor. If reusing rotor, clean with brake cleaner and ensure flatness. Reinstall rotor.
- Theory: clean, flat rotor gives consistent friction surface; contaminants reduce friction dramatically.
9. Clean guide pins and bores, remove old grease, inspect boots. Lubricate pins with high-temp brake grease and reinsert. Replace any corroded pins/boots.
- Theory: smooth sliding of caliper keeps pads parallel and prevents dragging/uneven wear.
10. Compress caliper piston(s) slowly with a piston tool or C-clamp using the old pad as a backing plate. Watch brake fluid reservoir — remove excess if it approaches overflow.
- Theory: piston must be retracted to make room for thicker new pads; slow compression prevents sudden pressure and avoids forcing fluid into overflow.
11. Install new anti-rattle clips/hardware. Fit new pads into position—ensure orientation (shims/wear indicators facing correct way).
- Theory: new hardware secures pads, reduces noise and ensures consistent seating.
12. Refit caliper over new pads and rotor, torque caliper bolts to factory spec, install wheel and snug lug nuts by hand.
13. Lower vehicle to ground and torque lug nuts to factory spec with a torque wrench.
- Theory: correct torque prevents wheel loosening or warping.
14. Pump brake pedal slowly until firm and pads seat against rotors. Check brake fluid level and top if needed.
- Theory: seating removes the small gap and sets pad contact; fluid level control prevents overflow and air entry.
15. If caliper was opened to atmosphere and pistons were extended beyond their normal travel or you disturbed lines, bleed the brakes (start farthest wheel). Otherwise just confirm firm pedal.
- Theory: bleeding removes air — only incompressible fluid transmits pressure properly.
16. Bed-in procedure: perform several controlled stops from ~30–35 mph down to 5–10 mph (not to full stop) with moderate braking, then a few normal stops. Avoid heavy repeated full stops for first 200 miles.
- Theory: bedding transfers an even, thin layer of pad material to rotor for stable friction coefficient; skipping bedding causes uneven transfer and reduced braking.

5) What to watch for after repair (diagnosis verification)
- Firm, non-spongy pedal: hydraulic and bedding success.
- No dragging (wheel temperature should be OK after a drive): indicates pins are sliding and caliper not seized.
- No vibration or pulsation: rotor flatness acceptable.
- Even pad wear on subsequent inspections: proper caliper function.

6) Common pitfalls and why they matter
- Not lubricating guide pins → sticky caliper → uneven wear and overheating.
- Reusing severely worn/warped rotors with new pads → vibration and rapid pad glazing.
- Pushing piston back too fast or letting reservoir overflow → contaminated or lost fluid; possible master cylinder damage.
- Letting caliper hang on hose → hose stress and possible failure.

7) Disposal and final notes
- Dispose of old pads/fluids per local regulations (asbestos concern in very old pads).
- If any unusual wear patterns or leaking boots are present, replace caliper or hoses — pads alone won’t cure hydraulic or mechanical brake faults.

This sequence and the included theory explain not only how to replace the pads but why each action corrects the underlying faults.
rteeqp73

TOYOTA 22RE ENGINE REBUILD - Part 1/2 - Teardown and analysis of a poor running 22R Toyota legend... My 1985 Celica GT Coupe was barely running when I bought it, but I knew that I could bring the legendary 22R-E back to life!

#rusty #engine #block #22r #toyota #freezeplug #offroad #4wd #antifreeze

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