2000 MAZDA B4000

Typical onset: 100,000-150,000 mi

Symptoms: rattling on cold start that quiets after 10-20 seconds, check engine light with cam/crank correlation codes, sudden loss of power and no-start if chain jumps, metal shavings in oil

Fix: Requires front cover removal, replacement of all guides, cassettes, tensioners, chains, and often cam phasers. 12-16 labor hours. If chain jumped and valves kissed pistons, you're looking at heads-off work or full engine rebuild.

Estimated cost: $2,800-5,500

Typical onset: 80,000-140,000 mi

Symptoms: milkshake-looking transmission fluid, transmission slipping or erratic shifts, coolant level dropping without external leaks, overheating transmission

Fix: Steel cooler lines rust through at radiator fittings, allowing coolant into ATF. Requires radiator replacement, full transmission flush or rebuild if contamination occurred, and new cooler lines. If caught early, flush and lines: 4-6 hours. If trans damaged: add 10-14 hours for rebuild.

Estimated cost: $800-1,200 (lines/flush), $2,500-3,800 (with rebuild)

Typical onset: 90,000-130,000 mi

Symptoms: coolant smell from engine bay, white smoke on startup, coolant loss with no external leaks, rough idle or misfire when cold

Fix: Plastic composite intake manifold warps, lower gaskets fail. Must remove upper and lower intake, replace all gaskets and often the thermostat housing while you're there. 6-8 labor hours.

Estimated cost: $900-1,400

Typical onset: 70,000-110,000 mi

Symptoms: clunk when shifting from park to drive or reverse, excessive vibration at idle in gear, visible engine/trans sag when inspected from below

Fix: Rubber mount deteriorates. Simple replacement, often done with transmission support jack. 1-1.5 labor hours.

Estimated cost: $180-320

Symptoms: sudden misfire, hissing or loud exhaust leak sound from engine, plug blown out of head with threads stripped, loss of compression on one cylinder

Fix: Aluminum heads have shallow spark plug threads that strip under heat cycling or overtorque. Requires Heli-Coil or Time-Sert thread insert, sometimes head removal if insert kit can't be used in-situ. 2-5 hours depending on cylinder access and whether head comes off.

Estimated cost: $350-900

Typical onset: 100,000-160,000 mi

Symptoms: intermittent stalling, no-start with no fuel pump whine, loss of power under load, starts after sitting but dies when warm

Fix: Module mounted on frame rail near fuel tank fails due to heat and corrosion. Replacement is straightforward, 1-1.5 hours, but part is dealer-only and expensive.

Estimated cost: $400-650

Typical onset: 80,000-150,000 mi

Symptoms: gear oil dripping from pinion flange, whining noise from rear axle if fluid runs low, oil residue on driveshaft and diff housing

Fix: Pinion seal hardens and leaks. Driveshaft removal, crush sleeve and bearing preload reset. 2.5-3.5 hours if bearing preload stays in spec, more if pinion bearings are worn.

Estimated cost: $350-600