Mazda 5 CR

2.0-litre common-rail diesel in various development stages (RF4F, RF5C, RF7J). Solid everyday diesel with good torque.

• !! Interference Engine — Engine Damage on Timing Belt Failure from 80,000 km

  The RF diesel is an interference engine. If the timing belt snaps, pistons and valves collide — the cylinder head must be replaced. Change interval: 80,000 km or 8 years.

  Symptoms: Engine won't start after belt snap, no compression, metallic noises on start attempts
  300–400 $
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• !! Leaking Injection Pump (Solenoid Valve) from 100,000 km

  The solenoid valve beneath the injection pump leaks. Diesel seeps out and can attack coolant hoses and wiring looms. Diesel specialists replace only the valve rather than the entire pump.

  Symptoms: Diesel smell in engine bay, visible fuel moisture beneath the injection pump, swollen coolant hoses
  150–800 $
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• !! Injection Driver Module (IDM) Earth Fault from 130,000 km

  The Denso injection driver module (IDM, RF2A-18-701A) under the intake manifold develops earthing problems with age. Fault codes are often not set — difficult to diagnose.

  Symptoms: Engine barely responds to throttle when cold, jerky acceleration below 1,500 rpm, normal behaviour above 2,500 rpm
  200–600 $
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+ 4 more engine weaknesses + vehicle weaknesses

1.8-litre MZR four-cylinder from the L-series. Entry-level engine for mid-range and van applications, adequate for everyday use.

• !! Interference engine — catastrophic damage on belt failure from 120,000 km

  The L8 MZR is an interference engine. If the timing belt snaps, pistons hit valves — expensive engine damage. Mazda service interval approx. 120,000 km, better every 80,000–100,000 km.

  Symptoms: Engine will not start after belt failure, no compression, metallic noises on starting attempt
  450–800 $
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• ! Valve stem seals — oil consumption at high mileage from 160,000 km

  At high mileages (from around 150,000 km) the valve stem seals leak. Oil enters the combustion chambers, leading to elevated oil consumption and blue smoke.

  Symptoms: Blue smoke on cold start or after extended standing, dropping oil level with no external leaks
  250–600 $
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• ! Throttle body fouled and sticking from 90,000 km

  Carbon deposits on the throttle body cause a sticking mechanism and jerky pull-away. After cleaning, the throttle body must be re-adapted in the ECU.

  Symptoms: Sticking throttle, jerky pull-away, rough idle, occasional stalling
  50–200 $
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+ 2 more engine weaknesses + vehicle weaknesses

2.0 litre MZR, 160 hp — rougher and more characterful than the NB engines, more displacement, more torque. Not the sharp wail of the NA 1.6, but a broader growl. The NC-specific engine problem: sudden oil loss from coked 5W-30 at cylinder 4, especially NC1 (2005-2009). Fix: switch to 5W-50 after warranty and check oil level obsessively. VVT solenoid gets contaminated at high mileage. NC2/NC3 (from 2009) with revised internals are considerably more reliable. Buying an NC? NC2 or NC3. The NC was mocked as the Fat Miata — unfairly on a country road, fairly on the scales.

• !! Timing belt — interference engine, maintenance critical from 120,000 km

  The LF-DE is an interference engine. A snapped timing belt causes serious engine damage via piston-to-valve contact. Change interval 120,000 km; always replace water pump and idler pulleys at the same time.

  Symptoms: Engine will not start after belt failure, no compression, severe engine noise on starting attempt
  500–950 $
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• !! Thermostat failure — overheating or under-cooling from 100,000 km

  The thermostat of the LF-DE can fail from around 100,000 km — either sticking closed (overheating) or permanently open (under-cooling). Water pump often follows shortly after.

  Symptoms: Coolant temperature rises sharply or stays permanently low, heater produces no warmth
  80–300 $
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• ! Throttle body dirty from carbon deposits from 80,000 km

  Carbon deposits on the throttle ring cause a sticky mechanism and unstable idle. Particularly common on the Mazda6 GG — engine stalls on declutching.

  Symptoms: Engine dies when declutching or braking, hunting idle, throttle slightly sticky
  50–250 $
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+ 5 more engine weaknesses + vehicle weaknesses

2.3-litre four-cylinder from the L-series with chain drive. Strong torque and refined character, top naturally aspirated engine in the range.

• !! Conrod bearing failure due to oil starvation from 150,000 km

  The conrod bearings of cylinder 4 share their oil supply with the balance shaft. If oil level drops or the oil strainer is dirty, lubrication breaks down here first. Engine failure often occurs from 130,000–160,000 km without warning.

  Symptoms: Knocking engine noise as oil temperature rises, sudden power loss, heavy smoke
  2,000–5,000 $
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• !! Elevated oil consumption due to piston rings from 130,000 km

  The 2.3 MZR shows significant oil consumption at higher mileages, primarily due to worn piston rings. Replacing valve stem seals produced little improvement in documented cases.

  Symptoms: Oil consumption of 0.5–1.5 l per 1,000 km, light blue smoke under load, regular top-ups needed
  800–2,500 $
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• !! Timing chain elongates from 150,000 km

  From around 130,000 km the timing chain can elongate and overload the tensioner. No acute snap risk like the L3-VDT, but left unattended valve timing errors and rough running will follow.

  Symptoms: Rattling noise on cold start that fades at operating temperature, rough running at low revs
  800–1,500 $
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+ 3 more engine weaknesses + vehicle weaknesses