1) Quick theory summary (what the expansion/overflow tank does)
- Holds excess coolant expelled from the pressurised cooling system as it heats and expands; allows it back into the system as it cools.
- The cap + sealed tank maintain system pressure. Pressure raises boiling point and forces coolant through the engine/radiator; loss of pressure → boiling, overheating.
- Tank also houses the low-coolant level sensor and provides a visible level indicator for maintenance.
- Typical failure modes: cracked/plastic tank leaks, failed cap (loses pressure), faulty level sensor, brittle hose connections, or internal contamination/clogs. Any of these cause coolant loss, air ingress, poor heat transfer and overheating.

2) Safety and prep (don’t skip)
- Work only on a cool engine. Hot coolant/steam will severely scald.
- Wear eye protection and gloves. Have a drain pan and rags ready.
- Use the correct coolant for your Delica (manufacturer spec). Dispose of old coolant responsibly — it’s toxic.
- Tools: basic socket set, screwdrivers, hose-clip pliers, pliers, funnel, clean container, new clamps if needed, replacement tank (and cap/sensor if replacing), hand-held pressure tester (optional but recommended).

3) Diagnosis (verify the tank is the problem)
- Visual: cracks, wet spots, dried coolant residue around tank, hoses, or under the vehicle.
- With cold engine: remove cap and inspect for coolant level low, heavy contaminants, or visible cracks.
- Pressure-test the cooling system (pump tester): if it holds less than cap rating, inspect tank and hoses for leaks. A cap that does not hold pressure can mimic a bad tank.
Theory: confirm which component fails (cap vs tank vs hoses) so you replace only the faulty part.

4) Drain/relieve pressure (ordered step)
- Engine cold: slowly remove the expansion cap to relieve any slight pressure, then use a drain pan under the lowest radiator drain or loosen a lower hose clamp to drain enough coolant to drop level below tank hose connections.
Theory: you need the coolant level below disconnected hose ends to avoid a large spill and to remove the tank cleanly.

5) Disconnect electrical and hoses (ordered step)
- Unplug the level sensor connector.
- Use hose-clip pliers to release clamps and remove the inlet/outlet hoses from the tank. Catch remaining coolant.
- Label hoses or note locations if multiple lines exist.
Theory: level sensor and hoses must be removed to extract the tank; disconnecting electrical prevents damage.

6) Remove tank from mounts (ordered step)
- Remove mounting bolts/clips and lift the tank free.
- Inspect mounting rubber and bracket for corrosion or damage; replace if needed.
Theory: physical removal exposes tank for replacement. Inspecting mounts prevents repeating failure due to broken supports stressing a new tank.

7) Inspect related components (ordered step)
- Check hoses for soft spots, cracks or collapsing; replace any suspect hoses.
- Check hose clamps; replace rusty or weak clamps.
- Inspect the cap: if old, replace the cap even if tank is reused.
Theory: a new tank with old brittle hoses or a failed cap will not fully solve the problem.

8) Install new tank (ordered step)
- Transfer any fittings/o-rings from the old tank if provided and in good condition; replace seals if worn.
- Mount tank into place and secure bolts/clips to manufacturer spec.
- Reconnect hoses and clamps. Reinstall level sensor and plug in.
Theory: a new, sealed tank restores containment and proper hose routing; correct seals prevent leaks and air ingress.

9) Refill and bleed air from the system (ordered step)
- Refill with the correct coolant mixture using a funnel to the proper level in the expansion tank.
- Bleeding method (practical, general):
a) Leave radiator cap off (or expansion cap off) and start engine with heater on full hot and blower low. As engine warms, thermostat opens and bubbles will appear — squeeze upper radiator hose gently to help dislodge trapped air.
b) Continue topping up until bubbling stops and level stabilises.
c) When no more air is visible and engine reaches normal operating temperature, fit the cap and watch for stable level and no bubbles or boiling.
- If available, use a vacuum fill tool or pressure bleed pump: they remove air reliably and reduce headaches.
Theory: trapped air forms “air locks” that block coolant flow and cause local overheating. Proper bleeding ensures a complete liquid circuit and restores heat transfer efficiency.

10) Pressure-test and final checks (ordered step)
- Option A — pressure test the system with a hand pump to the cap rating (typically ~13–16 psi / 0.9–1.1 bar for many cars). Confirm it holds pressure and inspect for leaks at the new tank, hoses, sensor.
- Option B — run the car to operating temperature, check for no leaks, verify stable gauge temperature, confirm heater output, and re-check coolant level after cool-down; top up if needed.
Theory: verifying pressure ensures the cap and system are sealing. Holding pressure confirms the repair stopped the leak/air ingress.

11) How the repair fixes the fault (concise theory)
- Replacing a cracked expansion tank removes the leak path that was losing coolant and allowing air in. That restores coolant volume.
- Replacing a faulty cap restores correct system pressure, which raises boiling point and keeps coolant in the radiator/engine passages where it can transfer heat.
- Bleeding removes air pockets that previously impeded coolant circulation and heater performance.
- Replacing failed hoses or clamps removes additional leak/flow restrictions. Together, these restore closed, pressurised, full-volume cooling circulation — preventing local boiling and overheating and returning normal temperature control.

12) Aftercare and signs of success
- No external coolant leaks, steady coolant level after cool-down, stable temperature gauge, good cabin heat, no steam or boil-over from reservoir.
- Re-check after a short test drive and again after a few days of driving.

Estimated time
- 1–2 hours typical for a straightforward replacement; longer if hoses, sensors or fittings need replacement or if extensive bleeding is required.

That’s the ordered procedure plus the underlying reasons for each action.
rteeqp73

Auction JDM Mitsubishi Delica L300 - The Forgotten 4x4 Van While at an auto auction, I came across this JDM Mitsubishi Delica L300 Star Wagon. Why is this car here at a vehicle auction?

Mitsubishi Delica - JDM Off-Road MINIVAN?!?! #Shorts

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1) Overview (theory up front)
- Function: the master cylinder converts pedal force into hydraulic pressure. Hard steel lines transmit that pressure to flexible hoses and calipers/wheel cylinders. Any leak or internal collapse reduces pressure or admits air, causing a soft pedal or loss of braking.
- Objective of the repair: restore a continuous, leak‑free, correctly flared and clamped fluid path so pressure from the master cylinder is delivered to the brakes. After replacement you must remove air from the system so the hydraulic circuit contains only incompressible brake fluid.

2) Safety and preparation
- Safety theory: brake work directly affects stopping ability. Work on a flat surface, chock wheels, use jack stands (never just a jack). Prevent fluid contacting painted surfaces or skin; brake fluid is corrosive.
- Gather parts/tools: correct replacement lines (pre‑formed or straight tube + bender), correct flaring tool (for SAE double flares or the flare spec for your vehicle), new flexible hoses if needed, new copper crush washers for banjo fittings, flare nuts, retaining clips/brackets, brake fluid DOT spec required for the Delica (use the spec on the reservoir cap), line wrenches, flare nut wrench, tube cutter, brake bleeder or vacuum pump, catch container, rags, safety glass, torque wrench, jack/stands.
- Theory: using the right materials and flare type ensures metal‑to‑metal seals and corrosion resistance; wrong flares or crushed tubing leak under pressure.

3) Isolate and protect master cylinder
- In order: top off master cylinder so reservoir does not run dry; use a clean cap or plug the master cylinder outlet ports with proper plugs or threaded adapters if available.
- Theory: preventing contamination and air ingress protects internal seals and makes subsequent bleeding easier. If you let the reservoir go dry you must bench‑bleed and be certain no contaminants enter.

4) Vehicle access and drain
- Lift vehicle, support safely, remove the wheel(s) for access to the lines and calipers/wheel cylinders.
- Place a catch container under the lines and open the bleed screws slightly if you will disconnect the caliper end first to control fluid flow.
- Theory: draining reduces spills and exposure of lines to brake fluid which damages paint/rubber.

5) Remove the old line (logical order)
- Recommended order: disconnect at the caliper/wheel cylinder end or at the flexible hose union first, then work back toward the master cylinder. Unclip retaining brackets and remove any rusted sleeves.
- Practical reason: disconnecting at the far end first lets fluid drain out while the master end stays sealed (if you plugged it), reducing contamination. It also avoids unscrewing the master cylinder ports, which can be messy and introduce more air.
- If using pre‑bent replacement lines, unbolt mounting brackets and carefully remove the hard line from clips.

6) Prepare replacement line and fittings (theory of flares)
- If fitting a new line made from straight tube, bend only with a tube bender to maintain internal bore; cut square and deburr, make a proper double (45°) flare consistent with DOT/SAE practice unless your manual specifies another type.
- Theory: a proper double flare is two metal layers thick at the sealing face, preventing the flare from cracking or deforming under brake pressure. Single/bubble flares will leak on fittings designed for double flares.

7) Install the new line in order
- Route the line exactly as original, secure it with new clips/brackets so it cannot rub or vibrate through corrosion.
- Connect the line ends. Where the hard line meets a flexible hose use the correct flare nut. Where a banjo fitting is used (caliper) use new copper crush washers on both sides of the banjo and torque the bolt to spec.
- Always tighten fittings to factory torque spec; if unknown, consult a manual. Theory: correct torque compresses the flare or crush washer to form a leak‑free seal without overstressing the fitting.

8) Reconnect and refill
- Remove plugs from master cylinder ports (if used), top up reservoir with correct fluid.
- Bench‑bleed the master cylinder if it was emptied or if you removed it. Theory: bench bleeding removes trapped air in the master cylinder bore so it does not feed air back into the system during hose replacement.

9) Bleeding sequence and method (why in that order)
- Bleed brakes starting with the wheel farthest from the master cylinder, then next farthest, finishing with the closest. (If uncertain which is farthest, follow the vehicle manual; typical order is rear passenger, rear driver, front passenger, front driver on many layouts.)
- Use a vacuum or pressure bleeder or the pump‑and‑hold/assistant method. Continue until clear, bubble‑free fluid emerges and pedal feels firm.
- Theory: air rises in the lines and the furthest caliper holds the most air; bleeding that first shortens the path air must travel out of the system. A firm pedal indicates a system full of incompressible fluid and no internal leaks.

10) Inspection, torque check, and test
- With system pressurized, inspect all new joints for leaks while an assistant holds steady pedal pressure (or use a pressure bleeder). Recheck torque after initial pressure cycles.
- Lower vehicle, road‑test at low speed in a safe area, check pedal firmness and braking balance, then re‑inspect for leaks.
- Theory: cycling the system seats seals and exposes any fittings that were not properly sealed or torqued.

11) Why this repair fixes the original faults (summary)
- Corroded or ruptured lines cause external leaks (loss of fluid) and/or internal collapse/corrosion that can restrict flow or trap air. Replacing the line restores a continuous metal path able to handle hydraulic pressure, removing leak paths and restoring volumetric integrity.
- Correct flaring, new crush washers, and proper routing/clipping prevent new leaks and future chafing. Bleeding removes air so the system transmits pedal force correctly. Together these actions restore the hydraulic efficiency and safety of the braking system.

Final safety notes (no fluff)
- Use the correct DOT fluid and dispose of contaminated fluid properly. Replace flexible hoses if old or cracked. If unsure about flare spec, torque numbers, or if corrosion is extensive in hard‑to‑reach areas, have a qualified shop do the work. After repair, perform thorough leak checks and a cautious road test.
rteeqp73