1991 JAGUAR XJ6

Typical onset: 80,000-120,000 mi

Symptoms: Coolant loss with no visible external leaks, White smoke from exhaust on cold start, Milky oil on dipstick or oil cap, Overheating under load or in traffic, Rough idle or misfire after warming up

Fix: Both head gaskets typically fail due to block/head warping from overheating episodes. Requires heads removal, resurfacing (often 0.010-0.015 in), new gaskets, timing chain components inspection, and thermostat/water pump replacement while open. 18-24 labor hours at an indie shop familiar with the AJ6.

Estimated cost: $2,800-4,500

Typical onset: 70,000-110,000 mi

Symptoms: Transmission fluid pooling under engine bay or mixing with coolant (strawberry milkshake in radiator), Harsh or delayed shifts after radiator work, Transmission slipping or refusing to engage gears, Pink residue in coolant expansion tank

Fix: Steel cooler lines rust through or rubber hoses burst; worse, internal radiator cooler can fail and mix coolant into transmission fluid, which kills the ZF within miles. Repair involves replacing all cooler lines, external cooler install (recommended), flushing transmission completely, and often full transmission rebuild or replacement if contamination occurred. 12-16 hours for full cooler system plus transmission R&R if needed.

Estimated cost: $1,200-3,800

Symptoms: Power windows dropping into doors or moving slowly/intermittently, Central locking cycling on its own or failing to unlock, Instrument cluster lights flickering or gauges reading incorrectly, Intermittent no-start with no crank (ignition relay or inertia switch), Check engine light on with no stored codes

Fix: Classic Lucas wiring issues: corroded connectors behind kick panels, failed window regulators (plastic gears strip), door lock actuators, and instrument voltage stabilizer failures. Each subsystem is 2-4 hours diagnosis plus parts. Window regulators are $150-300 each plus 1.5 hours per door. Instrument cluster repair requires removal and soldering skills or specialist rebuild.

Estimated cost: $300-1,200

Typical onset: 60,000-100,000 mi

Symptoms: Excessive vibration at idle, especially with A/C on, Clunking when shifting from Park to Drive or Reverse, Visible engine movement when revving in Park, Driveline shudder on acceleration

Fix: Hydraulic engine mounts and transmission mount deteriorate, allowing powertrain to shift excessively. Requires lifting engine slightly to access. Replace all three mounts as a set. 4-6 hours labor.

Estimated cost: $600-1,000

Typical onset: 80,000-130,000 mi

Symptoms: Hard starting when hot or after sitting, Stumble or hesitation under acceleration, Stalling at idle after highway driving, Fuel pump whine audible from rear seat area

Fix: In-tank fuel pump (mounted in trunk-area well) fails or filter clogs from decades-old varnish. Filter is inline under car (1 hour), but pump requires dropping tank or access panel removal. Pump replacement is 3-4 hours.

Estimated cost: $400-900

Typical onset: any mileage—age-related

Symptoms: Coolant leak from front of engine (thermostat housing crack), Expansion tank cracked at seams, coolant dripping onto ground, Sudden overheating due to coolant loss, Steam from under hood

Fix: Plastic thermostat housing and expansion tank become brittle after 30+ years and crack without warning. Replace both preemptively along with upper/lower hoses, thermostat, and radiator cap. 3-5 hours labor.

Estimated cost: $500-850

Symptoms: Rear end sagging, especially with passengers or cargo, Pump runs continuously (loud whirring from trunk), Fluid leaks from rear spheres or accumulator, Uneven ride height side-to-side

Fix: Self-leveling hydraulic system uses pump, accumulator, and spheres; seals fail and fluid leaks. Can delete system and install coil spring conversion kit (4-6 hours) or rebuild original components (6-8 hours plus parts sourcing difficulty).

Estimated cost: $800-1,800