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Module 08: DIY Repairs

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Step-by-step procedures for the most common, high-value DIY repairs: brake pads, air filters, spark plugs, windshield wipers, and exterior bulbs — with full safety protocols for each.

Table of Contents

  1. Overview
  2. Prerequisites
  3. Objectives
  4. Theory
  5. Key Concepts
  6. Examples
  7. Common Pitfalls
  8. Cross-Links
  9. Summary

Overview

[!NOTE] This module is a stub. Full content is planned for a future expansion.

This module is the practical application of everything learned so far. Instead of theory, the primary content is step-by-step procedures for five common repairs that any car owner can safely perform at home with basic tools. Each procedure includes the required tools, safety prerequisites, the complete procedure, acceptance criteria (how to verify the job was done correctly), and the most common mistakes at each step.

Difficulty: Intermediate  |  Estimated time: 6 hours (reading + hands-on practice)

Prerequisites

  • [[cars-maintenance/modules/01_introduction]] — safety procedures; vehicle lifting
  • [[cars-maintenance/modules/03_tires-and-brakes]] — brake system theory (required before brake pad replacement)
  • [[cars-maintenance/modules/05_engine-fundamentals]] — ignition system theory (helpful for spark plug replacement)
  • [[cars-maintenance/modules/07_diagnostics-and-obd2]] — knowing what DTC prompted the repair

Objectives

By the end of this module, you will be able to:

  1. Replace front brake pads safely, including caliper piston compression, hardware lubrication, and bedding-in procedure
  2. Replace engine air filter and cabin air filter (no tools required on most vehicles)
  3. Replace spark plugs with correct gap, anti-seize application, and torque specification
  4. Replace windshield wiper blades correctly for hook-type, pinch-tab, and side-pin mounts
  5. Replace common exterior bulbs: headlights (halogen), turn signals, and brake lights
  6. Describe the "bedding-in" procedure for new brake pads and why it matters
  7. Explain when each repair should be done by a professional instead

Theory

Brake Pad Replacement — Full Procedure

Tools: Floor jack, jack stands, lug wrench, socket set (typically 10mm, 12mm, 13mm, 14mm), C-clamp or caliper piston tool, wire brush, brake cleaner, brake caliper lubricant (NOT grease on the pad friction surface).

Key concepts before starting: Which way does the caliper piston compress? (Most front calipers push straight in; some rear calipers must be wound in clockwise). Why must pads be bedded in? (New pads have a hard resin surface that must be heat-cycled off to expose the full friction compound).

Procedure: Remove wheel → inspect rotor → unclip pad wear indicator → remove caliper bolts → hang caliper (do not let it hang by the brake hose) → compress piston → clean caliper bracket → install new pads with correct hardware → apply lubricant to caliper sliding pins only → reinstall caliper → pump pedal before driving → bed-in procedure.

Spark Plug Replacement

Gap specification: use feeler gauge; iridium and platinum plugs should not have gap adjusted. Anti-seize compound: recommended on aluminum heads. Torque: typically 12–18 lb-ft for most 14mm plugs. Firing order: matters for marking coil wires on older vehicles (direct-injection coil-on-plug ignition means no wires to confuse). Inspect old plugs for diagnostic information.

Air Filter Replacement

Engine air filter location: typically a black plastic box connected to the intake tube. Most require one to four clips or screws — no tools on many vehicles. Inspect for rodent nests (especially in older or stored vehicles). Replace if visibly dirty or per interval.

Cabin air filter location: under glove box, behind glove box, or under dashboard depending on vehicle. Most replacement takes under 5 minutes. Heavy odors may require activated carbon filter upgrade.

Windshield Wiper Replacement

Hook-type (most common): Press the release tab, rotate the blade, and slide it off. Verify replacement blade hook size. Pinch-tab and side-pin variants require slightly different technique — usually covered by a card in the replacement package.

Exterior Bulb Replacement

Halogen headlights: touch glass with bare hands introduces oils that cause hot spots and premature failure — always use gloves or a cloth. Some vehicles require bumper removal for headlight access — research before attempting. LED and HID headlights: do not DIY on HID without training (high voltage capacitors can discharge lethally even unplugged). Turn signals and brake lights: typically accessible from the trunk (rear) or through the wheel well (front corner) by removing a small panel.

Key Concepts

  • Bedding-in (brake break-in): Procedure of graduated heat cycles to transfer even layer of pad friction material onto rotor surface; prevents vibration and improves performance
  • Anti-seize compound: Thread lubricant applied to spark plug threads in aluminum heads; prevents seizure and thread damage during future removal
  • Caliper piston wind-in: Some rear brake calipers have integrated parking brake mechanisms requiring the piston to be wound clockwise (not just compressed) — doing it wrong damages the caliper
  • Double-gasketing: Forgetting to remove old filter gasket before installing new one; causes leak
  • Brake cleaning: Always clean rotors with brake cleaner spray before installing new pads — oil or grease on rotor surface causes immediate brake fade and squeal

Examples

To be fully written in complete module expansion:

  • Complete illustrated brake pad replacement procedure on a typical front-wheel-drive vehicle
  • Spark plug replacement with gap measurement and old plug condition assessment
  • Identifying which bulb replacement requires bumper removal vs. simple swap

Common Pitfalls

  • Not compressing the brake caliper piston before installing pads — pads won't fit and caliper won't close over the new (thicker) pads
  • Not pumping the brake pedal before attempting to drive — first pump after reassembly moves pads back to rotor contact; driving without this has no brakes for the first stop
  • Using grease instead of brake caliper lubricant on sliding pins — grease softens and runs onto friction surfaces; causes sticking calipers and squealing
  • Touching halogen bulbs with bare hands — contamination causes localized overheating and early bulb failure
  • Installing spark plugs without confirming gap — even "pre-gapped" plugs can be bumped during shipping
  • [[cars-maintenance/modules/03_tires-and-brakes]] — brake system theory required before performing brake repair
  • [[cars-maintenance/modules/05_engine-fundamentals]] — spark plug diagnostics (reading old plug condition)
  • [[cars-maintenance/modules/07_diagnostics-and-obd2]] — diagnosing misfire codes that lead to spark plug replacement
  • [[cars-maintenance/modules/12_capstone-project]] — all repairs in this module appear in the capstone inspection checklist

Summary

  • Brake pad replacement: compress piston, clean bracket, lubricate pins (not friction surfaces), torque caliper bolts, pump pedal, bed in with graduated stops
  • Spark plug replacement: confirm gap, use anti-seize on aluminum heads, torque to spec, inspect old plugs for diagnostic clues
  • Air and cabin filter: easy, no-tools jobs with significant impact on performance and air quality
  • Wiper and bulb replacement: critical for visibility; handle halogens with gloves; some headlights require access work
  • Safety first on every repair: lift safely, brake pedal pump before driving, verify no leaks before moving vehicle