Question 1

Structural Rust, Floors, Sills, Strut Towers

Accepted Answer

Perforations in the floor pans, sill (rocker panel) box sections, and front strut tower mounting points. In advanced cases, the floorboard flexes underfoot, the sills crumble when prodded, and the strut towers crack under suspension load. The Z-car was not well-protected from the factory. Minimal rustproofing, combined with seam-sealed joints that trap moisture, means water gets in and cannot get out. Australian coastal cars are worst affected, but any Z-car that has not been proactively rustproofed will have some degree of structural corrosion. Depends on severity. Surface rust can be treated with rust converter and encapsulated. Perforated floors require panel replacement, either reproduction floor pans (available from US suppliers like Tabco and Motor Sport Auto) or custom fabrication. Sill replacement requires cutting out the old box sections and welding in new steel, a job for an experienced panel beater. Strut tower repair is critical and must be done properly, poor repairs compromise handling and safety. Budget $5,000-20,000+ for comprehensive structural rust repair, depending on severity.

Question 2

Battery Tray Corrosion

Accepted Answer

The battery tray (right-hand side of engine bay on RHD cars) corrodes and eventually perforates. Rust spreads into the inner guard and firewall. Battery acid vapour attacks the steel. Older cars with non-sealed batteries are particularly vulnerable. Even sealed batteries produce enough vapour to cause damage over decades. Replace the battery tray. Reproduction trays are available ($100-250). If rust has spread into the inner guard, the surrounding metal must be cut out and replaced. Prevent recurrence by coating the new tray with POR-15 or similar rust encapsulator and fitting a sealed battery.

Question 3

Spare Wheel Well Rust

Accepted Answer

The floor of the boot around and beneath the spare wheel well rusts through. Water pooling is visible in the boot. Water enters through deteriorated taillight seals, boot seal, and rear hatch seal. It pools in the spare wheel well with nowhere to drain. Trapped moisture rusts the metal from both sides. Replace taillight seals and boot/hatch seals first to stop water ingress. Cut out rusted metal and weld in repair panels. Reproduction spare wheel wells are available from specialist suppliers. Coat the repaired area with POR-15 and cavity wax the enclosed sections.

Question 4

Rear Quarter Panel Rust

Accepted Answer

Rust appears behind the rear wheels, often starting as bubbles under the paint and progressing to perforations. Road spray from the rear wheels is thrown against the inner guard, which is a double-skinned area that traps moisture. The outer skin rusts from the inside out. Repair panels are available for the lower rear quarters. The job requires cutting out the affected area, treating the inner skin, and welding in the repair panel. This is panel-and-paint work, budget $1,500-3,000 per side for a professional repair.

Question 5

SU Carburettor Wear and Tuning Issues (240Z, 260Z)

Accepted Answer

Poor idle, hesitation on acceleration, rich or lean running, black smoke, poor fuel economy, difficult starting. The engine may run well at some RPMs but poorly at others. The twin SU carburettors use a sliding piston (suction chamber) that rises and falls based on engine vacuum. Over decades, the throttle shafts wear in their bores, creating vacuum leaks that cannot be compensated for by adjustment. The needle and jet wear, the float valve leaks, and the damper oil evaporates. SU carburettors are precision instruments that require regular maintenance, and most Z-car SUs haven't had it. A full rebuild addresses all wear items: new throttle shaft bushings (if the bodies are not too worn), new needles, new jets, new float valves, new gaskets, and new damper oil (light machine oil, 20W). Cost: $400-800 in parts for a pair. Finding someone who can properly tune SU carburettors is increasingly difficult, this is a dying art. Alternatively, many owners convert to Weber DCOE sidedrafts ($1,500-3,000 for a pair with manifold) or electronic fuel injection (Haltech, Link, or MegaSquirt, $2,000-4,000 including sensors and wiring).

Question 6

Fuel Injection Faults (280Z)

Accepted Answer

Hard starting (especially cold), rough idle, hesitation, rich or lean running, stalling. The engine management warning light may illuminate. The Bosch L-Jetronic fuel injection system uses an airflow meter (AFM) with a mechanical flap that wears with age. The cold start injector and thermo time switch fail. Injector seals harden and leak. The electronic control unit (ECU) can develop dry solder joints. Wiring connectors corrode, creating intermittent faults. Start with the basics: clean or replace the AFM ($200-500 used, very hard to source new), replace injector seals ($50-80 for a set), clean the cold start injector, test the thermo time switch, and inspect all wiring connectors for corrosion. For a permanent solution, many owners convert to modern aftermarket EFI, a Haltech or Link ECU with new injectors eliminates all age-related injection issues and makes the engine far more tuneable. Cost: $2,000-4,000 for a quality conversion.

Question 7

Timing Chain Stretch

Accepted Answer

Rattling or slapping noise from the front of the engine, particularly on cold start. The noise may diminish as the engine warms but does not fully disappear. The L-series uses a single-row timing chain (on early engines) or double-row chain (later engines) with a hydraulic chain tensioner. Over time, the chain stretches and the tensioner guides wear. The tensioner compensates up to a point, but eventually the chain becomes excessively loose. Replace the timing chain, tensioner, and guides. A double-row chain conversion kit is available for single-row engines ($200-400) and is strongly recommended. The job requires removing the radiator, fan, and timing cover. It is a full day's work but well within the ability of a home mechanic. Do not ignore excessive chain noise, a severely stretched chain can jump a tooth, causing valve timing to shift and potentially causing valve-to-piston contact.

Question 8

Head Gasket Failure

Accepted Answer

Coolant loss with no visible external leak. White smoke from the exhaust. Milky residue on the oil filler cap. Overheating. Coolant in the oil or oil in the coolant. The L-series head gasket is a composite design that deteriorates with age, thermal cycling, and overheating events. The long inline-six cylinder head is prone to distortion if overheated. Replace the head gasket. The head must be removed and checked for flatness, have it machined if distorted (0.05 mm maximum distortion is the limit). While the head is off, replace the valve stem seals and inspect the cam and followers. Cost: $300-600 for parts (gasket set, head bolts, valve seals), plus machining ($150-300). A competent home mechanic can do this job in a weekend.

Question 9

Valve Stem Seal Deterioration

Accepted Answer

Blue-grey smoke on startup (after the car has been sitting). Blue smoke on deceleration (lifting off the throttle after sustained acceleration). Oil consumption increases, typically 1L per 2,000-3,000 km. The original valve stem seals are rubber and harden with age, losing their ability to prevent oil from seeping past the valve stems into the combustion chambers. Replace the valve stem seals. This can be done with the head in place using a valve spring compressor and compressed air to hold the valves up (feed air into the spark plug hole with a fitting). Cost: $50-100 for a seal set. The job takes 3-4 hours. If the car is consuming significantly more than 1L per 3,000 km, the valve guides may also be worn and require replacement (head must come off for this).

Question 10

Rear Wheel Bearing Wear

Accepted Answer

Humming or grinding noise from the rear, increasing with speed. The noise may change tone when turning (loading one side more than the other). The rear wheel bearings on Z-cars are a known wear item. They are tapered roller bearings that require periodic adjustment and eventually wear beyond the adjustment range. Replace the rear wheel bearings. This requires a press to remove and install the bearings. The half-shaft must be removed, the bearing pressed off, and a new bearing pressed on. Cost: $100-200 per side in parts. Not a particularly difficult job but requires access to a press.

Question 11

Differential Mount Bushing Wear

Accepted Answer

Clunking from the rear on acceleration, deceleration, and gear changes. The clunk is felt through the car, not just heard. The differential is mounted to the rear subframe with rubber bushings that perish with age. As the rubber deteriorates, the diff moves under load, causing the clunking. Replace the diff mount bushings. Polyurethane replacement bushings are available and far more durable than the original rubber ($80-150 for a set). The job requires supporting the diff, removing the old mounts, and pressing in new bushings. Some owners upgrade to solid aluminium mounts for track use, but these transmit significantly more noise and vibration.

Question 12

Gearbox Synchro Wear (5-speed)

Accepted Answer

Grinding or crunching when shifting into 2nd or 3rd gear, particularly on quick shifts or cold starts. The synchro rings wear with age and enthusiastic use. Second gear takes the most abuse in normal driving. A gearbox rebuild with new synchro rings, bearings, and seals. Cost: $1,000-2,000 for parts and labour. Alternatively, a good used gearbox can be sourced for $500-1,000. The 280Z 5-speed is the strongest unit and the most desirable replacement.

Question 13

Earth/Ground Issues

Accepted Answer

Dim or flickering lights, erratic gauge readings, intermittent electrical faults that come and go. The engine may misfire or run poorly. The Z-car uses a single-wire electrical system with the body as the return path (earth). Over 50 years, every earth point corrodes, increasing resistance and causing voltage drop. This affects everything from the headlights to the ignition system. Clean every earth point on the car. There are approximately 15-20 earth points, on the engine block, body, dashboard, and rear. Sand the contact area back to bare metal, apply dielectric grease, and retighten. Adding supplementary earth straps (engine to firewall, body to battery) is cheap and effective insurance. Cost: virtually free. Time: 2-3 hours.

Question 14

Wiring Harness Deterioration

Accepted Answer

Intermittent electrical faults, burnt connectors, melted wire insulation. In extreme cases, electrical fires. The original wiring insulation becomes brittle with heat and age. Connectors corrode. Previous owners have spliced into the harness for accessories, often poorly. Inspect the entire harness, paying particular attention to the engine bay (heat exposure) and the area behind the dashboard. Replace damaged sections. For a car undergoing restoration, a complete reproduction wiring harness is available from companies like Wiring Specialties ($600-1,200) and is well worth the investment.

Question 15

Combination Switch Failure

Accepted Answer

Turn signals, headlights, or wipers stop working intermittently or permanently. The combination switch (stalk) on the steering column wears internally. The electrical contacts corrode and the plastic components crack. Replace the combination switch. Used units are available from wreckers but may have the same wear. Reproduction units are available for some models ($150-300). Disassembly and cleaning of the internal contacts can sometimes restore function.

Question 16

Overheating

Accepted Answer

Temperature gauge climbs into the danger zone, particularly in traffic or on hot days. Coolant loss from the overflow. Multiple factors compound on old Z-cars: a radiator that is partially blocked with scale, a thermostat that is stuck or partially open, a water pump with worn impeller, collapsed coolant hoses (the lower hose is most susceptible, it needs a spring insert to prevent collapse under suction), and a cooling fan that is not pulling sufficient air (the viscous clutch on the engine-driven fan wears out). Address all components systematically. A new aluminium radiator ($300-600) with more capacity than the original brass unit is a worthwhile upgrade. Replace the thermostat ($20-30), water pump ($80-150), all coolant hoses ($100-200 for a complete set), and the fan clutch ($80-150). A thermo-fan conversion (electric fan with a thermal switch) is popular and frees up engine power. Cost: $200-400 for a quality setup.

Question 17

Worn Bushings (All Suspension Points)

Accepted Answer

Vague steering, clunking over bumps, wandering at highway speed, uneven tyre wear. Every rubber bushing in the suspension is original and has exceeded its service life many times over. The control arm bushings, sway bar bushings, strut top mounts, and rear trailing arm bushings all deteriorate with age. Replace all suspension bushings. A complete polyurethane bushing kit is available from companies like Energy Suspension and SuperPro ($400-800 for a full car set). This is a significant job, allow a weekend for a complete suspension refresh including new ball joints, tie rod ends, and shock absorbers. The result is transformative: a Z-car with fresh bushings handles like a completely different car.

240Z / 260Z / 280Z

240Z / 260Z / 280Z known problems