1991 NISSAN 300ZX

Typical onset: 80,000-120,000 mi

Symptoms: blue smoke on deceleration, loss of boost pressure, grinding or whining noise from turbos, check engine light with lean codes

Fix: Turbos fail from oil starvation due to clogged oil feed lines or failed oil restrictors. Replacing turbos requires pulling the intake manifold, intercoolers, and downpipes — easily 18-24 hours of labor even for experienced techs. Most shops replace both turbos, all oil lines, restrictors, and gaskets as a package. Aftermarket turbos often preferred over OEM.

Estimated cost: $3,500-6,500

Typical onset: 60,000-90,000 mi intervals

Symptoms: coolant leak from front of engine, squealing on cold start, catastrophic engine failure if belt snaps

Fix: This is an interference engine — belt failure means bent valves and destroyed pistons. The job requires removing the entire front accessory stack, radiator, and fan shroud just to access covers. Plan 12-16 hours for timing belt, water pump, tensioners, and all seals. Non-negotiable maintenance item.

Estimated cost: $1,800-2,800

Typical onset: 100,000-150,000 mi

Symptoms: white smoke from exhaust, coolant loss with no visible leaks, overheating under load, milky oil, rough idle when cold

Fix: The VG30 is known for head gasket weeping, especially on turbo models that have been overheated. Requires pulling both intake and exhaust manifolds — the firewall clearance is absurd. Machine work for warped heads is common. Budget 24-30 hours for both banks, including coolant system flush and timing belt replacement while accessible.

Estimated cost: $3,500-5,500

Typical onset: 80,000-140,000 mi

Symptoms: long cranking before start, random stalling at idle, misfire codes, fuel smell in cabin, no-start when hot

Fix: Injectors clog or leak, and the CAS fails due to heat soak in the valley. Injector replacement requires plenum removal (6-8 hours). CAS replacement is 4-5 hours due to distributor access. Leaking injectors can wash down cylinder walls and cause bore scoring — don't ignore fuel smell.

Estimated cost: $1,200-2,200

Typical onset: 70,000-110,000 mi

Symptoms: clunking during shifts, vibration at highway speeds, drivetrain slop on throttle tip-in, visible tears in rubber mount

Fix: The transmission mount fails from age and torque abuse. The aluminum crossmember can crack at weld points. Requires exhaust removal and supporting the transmission. Mount replacement is 3-4 hours; crossmember reinforcement or replacement adds another 2-3 hours.

Estimated cost: $600-1,200

Typical onset: 90,000-130,000 mi

Symptoms: squealing belt that won't stay tight, loss of power steering, belt shredding, A/C failure, smoke from engine bay

Fix: The cramped engine bay causes heat buildup that kills accessory bearings prematurely. Seized compressor or PS pump can take out the serpentine belt and leave you stranded. Compressor replacement is 8-10 hours; PS pump is 5-7 hours. Both require removing radiator and fan shroud for access.

Estimated cost: $1,000-1,800

Typical onset: 80,000-120,000 mi

Symptoms: humming or grinding from rear, clunking over bumps, rear-steer feel during cornering, uneven rear tire wear

Fix: The rear multi-link suspension uses pressed bearings and rubber subframe bushings that degrade. Bearing replacement requires hub disassembly and a press (3-4 hours per side). Subframe bushings require dropping the entire rear cradle (8-10 hours for full refresh).

Estimated cost: $800-1,600

Typical onset: 70,000-110,000 mi

Symptoms: overheating in traffic or under load, coolant burping from overflow, fluctuating temp gauge, heater loss, warped heads if ignored

Fix: The twin-turbo cooling system is marginal from the factory. Plastic radiators crack, OEM radiator caps fail to hold pressure, and old hoses collapse. A full cooling system overhaul (radiator, hoses, thermostat, cap, flush) is 6-8 hours due to disassembly required. Preventive replacement avoids catastrophic head gasket or turbo damage.

Estimated cost: $1,000-1,800