IsItAGoodCar

Common Problems with the
1970–1978 Datsun 240Z / 260Z

We've identified 4 known issues that can affect the 1970–1978 Datsun 240Z / 260Z. 2 of these are serious faults that could be expensive to repair.

4
Known Issues
2
Serious
2
Moderate
0
Minor

All Known Issues

Structural Corrosion (Rust)

SeriousBodywork & Rust

The S30 chassis has many hidden box sections where moisture traps and eats the metal from the inside out. Frame rails, battery trays, and floor pans are the most common failure points.

Most affected: All models

Estimated cost: £5,000–£20,000+Affects: 1970–1978

Typical symptoms

  • •Bubbling paint
  • •Soft spots in floor/sills
  • •Doors not aligning (suggesting chassis flex)
  • •MOT failure for structural rot

What to inspect before you buy

  • ✓Magnet test on sills and arches
  • ✓Hammer tap on frame rails
  • ✓Check under the battery tray for acid/water damage

Overheating & Head Gasket Failure

SeriousCooling System

Older L24/L26 engines can suffer from silt buildup in the radiator or blocked coolant passages in the block, leading to localized overheating and warped heads.

Most affected: 240Z, 260Z

Estimated cost: £1,000–£3,000Affects: 1970–1978

Typical symptoms

  • •Temp gauge climbing in traffic
  • •White smoke from exhaust
  • •Mayo-like sludge under oil cap

What to inspect before you buy

  • ✓Condition of coolant (should be clean)
  • ✓Ask when the water pump/radiator was last replaced
  • ✓Test for exhaust gases in coolant

Carburetor & Fuel System Issues

ModerateFuel System

The Hitachi-SU carburettors require regular maintenance and adjustment. Worn needles, vacuum leaks and gummed-up passages cause flat spots, poor idle and hesitation. Parts are hard to source, with many owners converting to Webers.

Most affected: All models

Estimated cost: £200–£600Affects: 1970–1978

Typical symptoms

  • •Hesitation on acceleration
  • •Stalling at idle
  • •Rich or lean running
  • •Strong fuel smell

What to inspect before you buy

  • ✓Check for smooth throttle response through the range.
  • ✓Look for fuel leaks around carburettors.
  • ✓Inspect fuel lines for perishing.
  • ✓Ask if Weber conversion has been done.

Wiring Loom Degradation

ModerateElectrics & Electronics

After 45+ years, the original wiring loom becomes brittle. Corroded fuse connections, cracked insulation and perished earth straps cause intermittent electrical faults throughout the car.

Most affected: All models

Estimated cost: £100–£500Affects: 1970–1978

Typical symptoms

  • •Intermittent lighting failures
  • •Gauge erratic behaviour
  • •Flickering dashboard lights
  • •Blown fuses

What to inspect before you buy

  • ✓Inspect fuse box for corrosion.
  • ✓Check all earth points for clean metal contact.
  • ✓Test all electrical systems including lights and gauges.
  • ✓Consider a relay upgrade for headlights.

Buying Tips for the 1970 Datsun 240Z / 260Z

  • ✓Check the "doglegs" (the area in front of the rear wheels) and the floor-to-sill joins for soft metal.
  • ✓Ensure the engine starts easily and idles smoothly; L-series engines are famously "sweet" when tuned correctly.
  • ✓Look for signs of water ingress in the cabin, often caused by perished window seals or blocked scuttle drains.
  • ✓A "California Import" is often a safer bet for a project car, as UK-original cars have suffered through decades of salted roads.
  • ✓Upgraded electronic ignition is a common and highly recommended modification for modern reliability.

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Other Datsun 240Z / 260Z Year Periods

1970–1978

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