CKFCar Known Faults

Vauxhall Astra Astra H 1.7 CDTi 100bhp Known Faults

1.7 CDTi 100bhp2004–2010DieselManualHatchback20 known faults

What To Check Before Buying

  • ✓Check service history — was oil changed regularly?
  • ✓Look for blue/black smoke on startup and under load
  • ✓Listen for rattles, knocking, or turbo whine
  • ✓Test all electrics including windows, AC, and central locking
  • ✓Check for DPF warning light or recent regenerations
  • ✓Inspect for rust underneath and around wheel arches
  • ✓Request a pre-purchase inspection by an independent mechanic

Known Faults

Timing Belt Failure (Z17DTH)

Critical
2004-20101–60,000 miles£300–£500

Unlike the later Astra J (which has a chain), the Astra H 1.7 CDTi (Z17DTH engine) uses a timing belt. Belt failure is catastrophic on this interference engine. The service interval is 60,000 miles or 4 years.

Alternator Failure

Critical
2004-201070,000–120,000 miles£250–£400

The alternator on the 1.7 CDTi Astra is a notorious weak point. It fails without much warning, draining the battery and leaving the car stranded.

M32 Gearbox Bearing Failure

Critical
2004-201060,000–110,000 miles£400–£1200

If fitted with the 6-speed M32 gearbox, the Astra H suffers from catastrophic end-case bearing failure. A whining noise in 5th and 6th gear is the hallmark sign.

Injector Failure and Hard Starting

Severe
2004-201090,000–160,000 miles£250–£800

Injector failure on the Z17DTH engine causes misfires, rough running and in advanced cases prevents starting. The solenoid-type injectors used in this engine respond well to professional cleaning.

Alternator / Smart Charge System Failure

Severe
2004-201070,000–120,000 miles£250–£450

Modern vehicles use smart charging systems to reduce engine load, but the complex regulators on the alternators frequently fail.

Starter Motor Solenoid / Brush Wear

Severe
2004-201070,000–130,000 miles£150–£350

The starter motor wears out internally. This is particularly common on vehicles equipped with Stop/Start systems.

Clutch Slave Cylinder / Concentric Bearing Leak

Severe
2004-201070,000–120,000 miles£400–£800

The concentric slave cylinder (CSC) inside the gearbox bellhousing fails, leaking hydraulic fluid and causing clutch failure.

Suspension Coil Spring Snapping

Severe
2004-201060,000–120,000 miles£150–£300

A very common MOT failure in the UK. Suspension coil springs corrode and snap, usually near the bottom pigtail.

EGR Valve Failure

Moderate
2004-201050,000–100,000 miles£80–£350

The Isuzu-sourced Z17DTH and Z17DTJ engines in the Astra H have a well-documented EGR valve failure. Carbon deposits cause the valve to stick, resulting in power loss and increased emissions.

DPF Blockage

Moderate
2007-201040,000–90,000 miles£200–£800

DPF-equipped Astra H 1.7 CDTi models (post-2007) suffer from the same DPF blockage issues as most diesel Vauxhalls of this era. Urban use is the root cause.

Dual Mass Flywheel Failure

Moderate
2004-201080,000–150,000 miles£650–£1000

DMF wear on the Astra H 1.7 CDTi is a high-mileage inevitability. The flywheel's internal dampers lose effectiveness, causing vibration and judder that makes the car unpleasant to drive.

Sticking Brake Calipers (Slider Pins Seized)

Moderate
2004-201040,000–100,000 miles£80–£150

The floating brake caliper design relies on sliding pins. In the UK climate, salt and water ingress cause these pins to rust and seize solid.

Wheel Bearing Wear and Drone

Moderate
2004-201050,000–110,000 miles£120–£250

Wheel bearing wear is a normal consumable on UK roads, but frequent pothole strikes accelerate the failure rate significantly.

Glow Plug Failure / Snapping in Head

Moderate
2004-201060,000–110,000 miles£100–£300

Diesel glow plugs burn out over time causing cold starting issues. The major problem is they often snap in the cylinder head when mechanics try to remove them.

Shock Absorber Oil Leak and Failure

Moderate
2004-201070,000–120,000 miles£200–£400

Shock absorbers lose their damping efficiency over time, and eventually blow their seals, leaking hydraulic fluid.

Air Conditioning Condenser Leak (Stone Damage)

Minor
2004-201040,000–120,000 miles£250–£450

The air conditioning condenser is mounted at the very front of the cooling pack, making it highly susceptible to stone damage from the road, leading to refrigerant loss.

Front Anti-Roll Bar Drop Link Wear

Minor
2004-201030,000–80,000 miles£60–£120

The front anti-roll bar drop links wear out on heavily potholed UK roads, causing an annoying knocking sound at low speeds.

Electric Window Regulator Cable Failure

Minor
2004-201050,000–120,000 miles£100–£200

The cables inside the electric window regulator mechanism fray and snap, causing the window glass to drop into the door frame.

Engine Thermostat Sticking Open

Minor
2004-201060,000–120,000 miles£100–£250

The engine coolant thermostat fails in the 'open' position. The engine never reaches its optimal operating temperature, killing fuel economy.

12V Battery Degradation and Failure

Minor
2004-201030,000–150,000 miles£80–£250

Lead-acid and AGM batteries have a finite lifespan. Modern cars are highly sensitive to voltage drops, causing bizarre electrical faults before the battery completely dies.

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