Mazda 626
2.0-litre common-rail diesel in various development stages (RF4F, RF5C, RF7J). Solid everyday diesel with good torque.
Torque Shortage
The weak diesel struggles against the weight of a mid-size saloon. Economical, but no driving pleasure whatsoever.
Engine Weaknesses 7
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
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
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
The injector flame seals become porous and leak from around 120,000 km. Diesel mixture escapes and mixes with the engine oil, causing a sharp rise in oil consumption. A known production issue on the RF diesel engine.
Symptoms: Dark, heavily diluted engine oil; elevated oil consumption up to 1 litre/500 km; faint diesel smell at the engine.
The conical seating faces where the high-pressure fuel lines screw into each cylinder can develop leaks. Diesel smell after driving and persistently damp spots on the cylinder head are typical signs.
Symptoms: Strong diesel smell after shutdown; damp spots at line connections on the cylinder head; no visible leak when stationary.
The alternator of the RF diesel engine can fail from around 150,000 km due to bearing failure or regulator faults. The battery is no longer charged and the charge warning light illuminates.
Symptoms: Charge warning light on; battery discharges while driving; vehicle stalls.
The EGR valve carbons up and causes rattling noises and power loss. There are also wiring issues at the EGR electrics that promote temperature-dependent failures.
Symptoms: Rattling from the intake area, power loss especially after rain or cold start, impaired turbo response
Vehicle Weaknesses 8
The left fuel tank on the 626 GF can corrode internally and develop leaks. Complete through-rust has been documented in isolated cases and requires a tank replacement.
Nearly all 626 GF show rust on the rear wheel arches (10 o'clock position on the wheel arch), door folds and tailgate. Poor factory sealing is the main cause.
Rear brake calipers corrode and seize, especially after prolonged parking with the handbrake applied. The handbrake cable rusts and the adjustment mechanism fails.
Control arm ball joints and rubber bushings on the GF wear significantly with age. Trailing arms can corrode at the wheel hub connection. All four control arms and both trailing arms should be replaced together, as the parts wear interdependently.
Wheel speed sensors at the rear axle fail frequently, triggering an ABS warning. Individual sensors are cheap; a faulty control unit can be expensive.
The AC condenser and dryer on the GF become leaky with age and lose refrigerant. Running with insufficient refrigerant risks total compressor failure. The condenser and dryer should be replaced together.
The steering torque sensor on the GF, which measures the required steering force and controls the power assistance, can fail and lead to heavy or inconsistently assisted steering. The sensor is integrated into the steering system and can be replaced separately.
The faux leather on the steering wheel and gear knob cracks and peels after a few years. The driver's seat bolster also shows cracking. A purely cosmetic issue with no safety implications.