Isuzu Bighorn: common faults & what to check

Which Isuzu Bighorn are you looking at?

2 generation variants documented. Pick the shape you recognise: the faults, the servicing and the timeline below all narrow to it. Free, no account needed.

Petrol

1 variant documented

2000–2002UBS2000–2002UBS3.5 V6 petrolPetrolDocumented issues5 knownSee faults & what to checkPhoto: Vauxford via Wikimedia Commons, CC BY-SA 4.0.

Diesel

1 variant documented

2000–2002UBS2000–2002UBS3.0 turbo-dieselDieselDocumented issues10 knownSee faults & what to checkPhoto: Vauxford via Wikimedia Commons, CC BY-SA 4.0.

Now narrow it to the engine

A 1.8 and a 2.4 of the same car do not fail the same way, so the faults below narrow to the engine as well as the year. Free, no account needed.

Start your free check on this Isuzu Bighorn

No plate needed. You get the risk score, the buyer's checklist and the guided inspection for the exact car you picked above — not the whole nameplate.

The checks worth doing on a Isuzu Bighorn before you hand over any money. Every documented fault is listed below, each with its own page.

• Serious issue

  This is the one check to do before you drive anywhere.

  See why

  4JX1 injector sleeve seals — diesel finding its way into the oil or the coolant

  The 3.0 4JX1 diesel fitted to the last of these seals its injectors into the head with sleeves and O-rings, and those seals harden and shrink with age and heat. When they let go, diesel and combustion pressure escape where they should not: into the engine oil, which thins it out and starves the bearings, or into the cooling system, which turns the coolant into a foul brown emulsion. This is the single fault that gave the 4JX1 its reputation — some diesel specialists simply refuse to work on the engine because of it. A thinned, fuel-diluted sump destroys an engine quietly and quickly, so an oil level that keeps RISING is far more alarming than one that drops.

  What you would notice

  • Oil on the dipstick above full, thin, and smelling strongly of diesel
  • Brown or creamy sludge on the underside of the oil filler cap
  • Coolant in the header tank discoloured, oily-looking or smelling of fuel
  • Rough running or misfire once the engine reaches full operating temperature
  • Getting harder to start, especially from cold

  Typically $1,800–$6,500 to put right.

• Serious issue

  Probe sill seams and chassis box rails with a screwdriver — soft or holed metal is a fail.

  See why

  Sill, Chassis Rail and Undercarriage Rust (NZ JDM Imports)

  JDM Bighorns imported to NZ from Japan frequently show rust perforation at the lower sills, chassis rail box sections, floor pan edges and rear spring hanger mounts. New Zealand's coastal humidity and salt exposure accelerates rust on vehicles that spent their early years in Japan's rust belt prefectures. Perforated chassis rails cause WoF failures and are expensive or impossible to repair economically.

  What you would notice

  • Visible rust bubbling under paint on lower sills
  • Hollow sound when tapping chassis rails
  • Flaking rust from undercarriage visible on inspection
  • WoF rejection for chassis integrity

  Typically $1,200–$6,500 to put right.

• Serious issue

  Ask for documented timing belt service history.

  See why

  6VD1 3.2L V6 Timing Belt Failure (Interference Engine)

  The 6VD1 3.2L V6 is an interference engine with a 90,000 km timing belt replacement interval. Belt failure causes immediate and catastrophic valve-to-piston contact, bending valves and frequently cracking pistons. Many NZ JDM imports arrive with unknown belt service history, making this the single highest-priority pre-purchase check on petrol Bighorns.

  What you would notice

  • Engine stops suddenly without warning (belt breakage)
  • Rough or misfiring engine (partial belt wear)
  • Rattling from timing cover at startup
  • Coolant leak from water pump (often replaced at same service)

  Typically $700–$5,500 to put right.

• Costly issue

  Inspect the sills, door bottoms, wheel arches, rear body and chassis for rust, bubbling and past repairs.

  See why

  Sill and body rust

  The ageing Bighorn develops rust in the sills, door bottoms, wheel arches and rear body, a structural WOF concern in NZ. Corrosion is common on these older imported 4x4s.

  What you would notice

  • Rust in sills and door bottoms
  • Wheel arch corrosion
  • Rear body rust
  • WOF rust advisory

  Typically $400–$3,500 to put right.

• Costly issue

  Test TOD system engagement in a safe area — engage and disengage across the full range.

  See why

  Torque On Demand (TOD) 4WD Transfer Case Actuator Failure

  The electronically-controlled Torque On Demand 4WD system uses a transfer case actuator motor and electronic control unit that is prone to failure on high-mileage examples and on units that have sat unused for extended periods. Common failure modes include the actuator motor seizing, the encoder wheel cracking, and the ECU losing calibration, leaving the vehicle stuck in 2WD or unable to disengage 4WD. Parts availability is limited given vehicle age.

  What you would notice

  • TOD 4WD warning light illuminated
  • 4WD fails to engage or disengage
  • Grinding or clicking from transfer case area
  • Vehicle stuck in 4WD (binding on tight turns)

  Typically $900–$2,800 to put right.

• Costly issue

  Inspect the injection pump housing and shaft area for oil wetness.

  See why

  4JG2 Diesel Injection Pump Oil Seal Failure

  The 3.1-litre 4JG2 turbo diesel in the UBS69 Bighorn develops oil seal failure at the injection pump shaft. Hardened seals allow engine oil to seep from the pump body or, in worse cases, enter the fuel system. This fault is long-documented across the 4JG2 engine in both Isuzu Trooper and Bighorn applications in NZ and Australia. Age and heat cycling harden the pump seals; high mileage or vehicles that have not been run regularly are most susceptible. Repair requires injection pump removal for reseal or rebuild.

  What you would notice

  • Oil weeping from injection pump body or rear shaft seal area
  • Oil contamination visible on the pump housing and adjacent components
  • Engine oil consumption without apparent external engine oil leak
  • Diesel smoke or oil smell from engine bay after startup

  Typically $500–$1,200 to put right.

What these repairs cost on other cars

Some of the Isuzu Bighorn’s documented faults are repairs other models share. Each page lists the documented NZ cost for every model it affects.

• Cambelt Replacement Cost
• Diesel Injector Replacement Cost
• Turbo Repair and Replacement Cost

Other Isuzu models