Subaru Forester: common faults & what to check

Symptoms to notice

• White steam from exhaust that does not clear after warm-up indicating coolant in combustion
• Coolant loss with no external leak and milky contamination in the coolant header tank

What to check

Perform a cold engine start after overnight soak. White steam from exhaust that does not clear within 60 seconds of warm-up indicates coolant combustion. Check coolant header tank for oily film on the cap and milky contamination. A combustion leak test (block tester) on the coolant header confirms the failure definitively.

Symptoms to notice

• Oil level noticeably low between standard 10,000 km service intervals
• Occasional light blue smoke from exhaust at startup or under load
• Oil consumption exceeding 1 litre per 5,000 km
• No visible external oil leak but oil level drops consistently

What to check

1. 1.Pull the dipstick and note the oil level relative to service mileage.
2. 2.Ask the seller how often oil is topped up.
3. 3.Request an oil consumption test result if under warranty.
4. 4.Inspect the tail-pipe interior for oily carbon deposits suggesting oil burning.
5. 5.Check for any dealer correspondence or warranty claims relating to oil consumption.

Symptoms to notice

• DPF warning light on dashboard with reduced power mode
• Rough idle and hesitation under load
• Increased fuel consumption and black smoke under acceleration
• Failed forced regeneration attempt leaving DPF partially blocked

What to check

1. 1.Confirm no active regen is in progress and check DPF differential pressure sensor values.
2. 2.Inspect EGR valve operation for sticking — visible carbon deposits in the intake tract indicate heavy fouling.
3. 3.Check injector return flow rates as a worn injector contributes excess soot load.
4. 4.Confirm the vehicle has been regularly driven at sustained highway speeds to allow passive regen.
5. 5.If a workshop inspection is possible: Scan for DPF backpressure and soot load percentage via a diesel-compatible OBD-II tool.

Symptoms to notice

• Blue smoke from the exhaust on cold start that clears after the engine warms
• Oily residue or pooled oil inside the intercooler charge pipes
• Blue smoke during hard acceleration or when boost pressure rises
• Oil consumption elevated above 500ml per 5,000 km with no external leaks
• Oil smell from the engine bay under hard driving

What to check

On a cold start, observe the exhaust for blue smoke that appears briefly and dissipates as the turbo warms. During a hard acceleration run, watch the exhaust in a following vehicle's reflection or with a helper. Check the air filter housing and turbo compressor inlet for oil contamination. If a workshop inspection is possible: Remove the charge pipe from the intercooler outlet to the throttle body and inspect the interior surface for oily residue or visible oil pooling.

Symptoms to notice

• Rattling or chattering noise from the front of the engine for 3-10 seconds immediately on cold startup, disappearing once oil pressure builds — commonly described as a diesel-like clatter
• Check Engine light with misfire codes (P0301-P0304) or camshaft position sensor codes (P0341, P0346) indicating timing chain stretch has caused cam timing to shift
• Rough idle or loss of power with no obvious external cause, particularly after a high-mileage service interval with degraded oil
• Engine oil darker than expected for its service age, indicating oil quality degradation that accelerates guide and tensioner wear

What to check

During a cold-start inspection with the bonnet open, listen carefully at the front of the engine immediately on startup for chain rattle. Inspect the service history for evidence of regular oil changes at or before 7,500 km intervals — extended intervals are the primary cause of accelerated guide wear. A workshop with a bore scope can sometimes inspect the chain through the oil filler aperture. If a workshop inspection is possible: Use a scan tool to check for any stored or pending camshaft position or misfire codes.

Symptoms to notice

• Blue smoke from exhaust on engine braking and startup, especially on cold mornings
• Frequent need to top up engine oil between regular service intervals

What to check

1. 1.Check oil level at every fuel stop for two weeks — note consumption rate.
2. 2.Ask about typical trip lengths and whether the vehicle is mainly city or highway driven.
3. 3.Consumption of more than 1 litre per 5000km is abnormal for the FB20.

Symptoms to notice

• Check engine light with camshaft position codes P0011, P0021, P0012, or P0022
• Rough or lumpy idle, especially when cold
• Reduced low-RPM torque and sluggish throttle response
• Brief rattling from the valve cover area in the first seconds of cold start
• Poor fuel economy compared to expected figures for the engine

What to check

These codes may have been cleared but can reappear after a cold start. Ask about oil change intervals – engines serviced beyond 10,000 km on conventional oil are at higher risk. Listen for a brief rattling from the camshaft area during the first few seconds of a cold start. If a workshop inspection is possible: Connect an OBD-II scanner before purchase and check for stored or pending fault codes P0010, P0011, P0012, P0020, P0021, or P0022 (camshaft position actuator circuit or timing over-advanced/retarded).

Symptoms to notice

• Unexplained coolant level drop in the reservoir without visible external leak source
• Mild hybrid warning light if battery cooling circuit pressure drops below threshold

What to check

1. 1.Inspect the mild hybrid battery cooling system in the engine bay for any signs of coolant residue at hose connections.
2. 2.Check coolant level — unexplained drops may indicate a hybrid cooling circuit leak.

Symptoms to notice

• Flat spot under acceleration with audible hiss indicating boost pressure loss
• Power temporarily returning when throttle is released as the split pipe partially reseals

What to check

Firmly accelerate from 2000rpm and listen for hissing from the engine bay. Inspect intercooler pipes and joiners for cracking.

Symptoms to notice

• Rough or lumpy cold idle
• Hesitation on light throttle
• Cold-start misfire codes
• Oil residue in intercooler hoses

What to check

1. 1.Start the car stone cold and watch for a lumpy idle in the first minute.
2. 2.Ask whether the intake valves have ever been cleaned and whether a catch can/AOS is fitted (check the engine bay — a small canister with hoses near the intake).
3. 3.Pull the intake hose clamp back if the seller allows and feel inside for oil film.

Symptoms to notice

• EyeSight warning light illuminating on the dashboard, accompanied by a message that the system is temporarily unavailable, particularly after the car has been in direct sunlight
• Pre-collision braking system triggering unexpectedly on open roads with no obstacle present, or failing to warn of a genuine hazard
• Visible fogging, yellowing, or haze in the windshield area immediately in front of the camera housing that does not clear with the defroster
• Adaptive cruise control disengaging without driver input, with an EyeSight limitation message appearing in the instrument cluster

What to check

1. 1.Inspect the windshield in the area behind the camera mounting bracket with a torch at an angle — look for delamination bubbles, cloudiness, or discolouration.
2. 2.Start the vehicle and observe whether the EyeSight indicator illuminates green (operational) within 20 seconds of startup.
3. 3.Ask about any windshield replacements and whether dealer recalibration was performed afterward.
4. 4.If a workshop inspection is possible: Check for any EyeSight fault codes using Subaru Select Monitor or compatible scan tool.

Symptoms to notice

• Rattling or knocking noise that appears to come from the steering column or dashboard area when driving on uneven surfaces
• Vibration felt through the steering wheel rim over rough road surfaces that is absent on smooth roads

What to check

With the engine running (EPS active), have a second person slowly turn the steering wheel from lock to lock while you listen from the engine bay and under the dash for rattling or knocking. Drive over a series of small bumps and note whether the noise comes through the steering wheel. Check the steering rack mounting bolts for looseness. If a workshop inspection is possible: Connect a diagnostic scanner to check for any EPS torque sensor or motor fault codes.

Symptoms to notice

• Knocking or rattling from steering rack at low speeds
• Vibration through steering wheel during slow manoeuvring

What to check

Drive over rough surfaces at low speed and listen for rattle from the steering rack area.

Symptoms to notice

• Permanent TPMS warning light on dashboard with correct tyre pressures
• TPMS fault code stored (sensor not transmitting)
• Warning light appears after wheel rotation or tyre change
• System shows one or more sensors as missing

What to check

1. 1.Confirm TPMS warning light status at startup and after the vehicle has driven at least 5 minutes above 30 km/h.
2. 2.Scan for TPMS-specific fault codes using a compatible TPMS reset tool or Subaru-compatible scanner.
3. 3.Check that all four sensor IDs are registered in the system.
4. 4.Note that aftermarket steel rims without sensors will also trigger the fault permanently.

Symptoms to notice

• Rear end instability or a feeling of the car moving sideways during moderate to hard braking
• Uneven or diagonal rear tyre wear that recurs quickly after wheel alignment
• Clunking or thudding from the rear suspension over larger bumps or during directional changes

What to check

Check for rear tyre wear in a diagonal or feathered pattern indicating toe change. Observe the car tracking straight under moderate braking on a flat road. If a workshop inspection is possible: With the vehicle on a hoist at ride height (suspension loaded), inspect each rear arm bush for cracking, splitting, or visible rubber extrusion from the metal sleeve. Apply a pry bar carefully between the arm and subframe to check for excessive lateral play.

Symptoms to notice

• Clunking or knocking noise from the front suspension when driving over speed bumps, pot-holes, or rough surfaces
• Vague or wandering steering feel with the vehicle pulling to one side
• Uneven front tyre wear across the tread width indicating camber change from a worn joint

What to check

With the suspension at ride height, inspect the ball joint boot for tears, splits, or displaced grease. Have a second person turn the wheel lock to lock while you feel the lower arm for looseness or clunking. Check for uneven tyre wear consistent with toe or camber change. If a workshop inspection is possible: Raise the vehicle safely and grip the front tyre at the 6 and 12 o'clock positions, then rock it; excessive play indicates ball joint wear.

Symptoms to notice

• Steering shimmy or wobble felt through wheel at 90-110 km/h
• Clunk from front suspension over sharp bumps or road edges
• Vague or wandering straight-line tracking
• Vehicle pulling slightly under hard braking
• Accelerated inner tyre wear on the front axle

What to check

Visible movement or a soft compressible feel in the rear bush indicates wear. Inspect the bush visually for cracking, splitting, or deformation of the rubber element. Check front tyre wear pattern for uneven inner or outer edge wear suggesting caster change. If a workshop inspection is possible: With vehicle on a hoist, grasp the front lower arm and attempt to move it forward and rearward by hand.

Symptoms to notice

• Low-frequency humming or growling from the rear, changing with vehicle speed
• Noise louder on one side, varying when weight shifts during cornering
• Vibration felt through the seat or floor at highway speed
• Play detectable when rocking the wheel at 12 and 6 o'clock positions

What to check

Lift each rear wheel and check for play by rocking wheel; spin wheel by hand and listen or feel for roughness or grinding; road test at 80-100 km/h and listen for droning that changes with cornering load.

Symptoms to notice

• Clunking or knocking from the front suspension on bumps or cornering
• Vague or imprecise steering feel
• Pulling to one side under braking
• Uneven front tyre wear

What to check

Watch for: Clunking or knocking from the front suspension on bumps or cornering. If a workshop inspection is possible: Lift front wheels and check ball joint for play using a pry bar; inspect rubber boot for cracking or grease leakage; road test over rough surfaces and listen for clunking from front.

Symptoms to notice

• Clunking or knocking from front suspension over bumps
• Stiff or notchy steering feel, especially when turning slowly
• Resistance or grittiness felt through the steering wheel at parking speeds
• Uneven or sluggish steering return-to-centre

What to check

With car stationary, turn steering lock-to-lock and feel for binding or grinding at strut top; bounce each corner and listen for knocking; inspect strut top mount for cracking or deformation.

Symptoms to notice

• Humming or droning noise that changes with vehicle speed and varies on cornering
• Rumbling felt through steering wheel at highway speeds
• Vibration or pulsing through the floor under load
• Clicking or grinding when turning at low speed (advanced failure)

What to check

1. 1.Lift each front corner and spin the wheel by hand — listen and feel for roughness or grinding.
2. 2.Grip the tyre at 9 and 3 o'clock and attempt to rock it; any play indicates hub bearing wear.
3. 3.Test drive at 80-100 km/h and weave gently — if the noise changes as weight transfers left and right, the bearing on the quieter-load side is faulty.
4. 4.Inspect for any rust or corrosion on the hub face indicating water ingress.

Symptoms to notice

• Clicking from front when turning at slow speed or under power out of corners
• Grease spatter visible on inside of wheel arch near the CV boot

What to check

Inspect front CV joint boots for cracking and grease expulsion. A clicking sound from the front when turning at low speed confirms worn joint.

Symptoms to notice

• Vehicle pulling to one side under braking
• One disc hotter than the other after moderate use

What to check

1. 1.Check for pulling under braking.
2. 2.Feel for uneven wheel heat.
3. 3.Inspect guide pins.

Symptoms to notice

• Crack running up from the bottom edge of the windscreen
• History of multiple windscreen replacements
• Chips that spread unusually fast

What to check

1. 1.Inspect the windscreen edge-to-edge in good light, especially along the bottom near the wipers.
2. 2.Ask how many windscreens the car has had.
3. 3.If it has been replaced, ask whether an EyeSight recalibration was done and get the invoice — an uncalibrated EyeSight system can disable safety features.

Symptoms to notice

• Knocking from rear suspension over rough surfaces
• Imprecise rear handling and inner tyre edge wear

What to check

1. 1.Inspect rear suspension arm bushes for cracking.
2. 2.Push arms — any movement indicates worn bushes.
3. 3.Check rear tyre wear.

Symptoms to notice

• Clunk from the front over speed bumps or driveways
• Vague or wandering steering
• Uneven front tyre wear on the inner edges
• Recent WoF sheet noting suspension wear

What to check

Look at the front tyres for uneven inner-edge wear. Bounce each front corner and listen for knocks. Ask to see the last WoF checksheet — bushings and ball joints show up there first. Peer behind each front wheel at the big rear control-arm bush for cracked, extruded rubber.

Symptoms to notice

• Humming or growling from the rear that rises with road speed
• Noise changes when swerving gently left/right
• Droning that sounds like coarse-chip road on smooth seal

What to check

On the test drive, get to 80-100 km/h on smooth seal, drop the rear windows slightly and listen for a hum from the back. Gently weave in the lane — bearing noise changes with load direction. With the car jacked (or ask the seller), rock the rear wheels at 12 and 6 o'clock for play. Check service history for repeated bearing replacements — a genuine Subaru bearing is the fix that lasts.

Symptoms to notice

• Creaking or popping noise from the front of the cabin — often described as coming from the dashboard or footwell area — triggered by body twist during cornering or over uneven surfaces
• Noise is most pronounced in cold conditions (below 10°C) and may disappear once the vehicle warms up, making it difficult to reproduce for a dealer
• Creaking that changes character when a passenger is in the front seat versus when the vehicle is driven solo, indicating a body torsion sensitivity
• Dealer inspection finding no worn suspension components, with the noise source traced to the body structure itself rather than any mechanical part

What to check

1. 1.During a cold-weather test drive, drive over a series of speed bumps diagonally to induce body twist and listen for creaking from the A-pillar or firewall area.
2. 2.Ask the seller if the creak has been investigated at a dealer and whether any Subaru technical service action was applied.
3. 3.Check Subaru's own campaign database for any registered body-creak rectification on the specific VIN.

Symptoms to notice

• Rattling or clunking noise from the front suspension that is most pronounced when driving over small sharp road imperfections such as expansion joints or cat-eyes at low speed
• Noise changes character or disappears when the vehicle is leaned hard into a corner (which pre-loads the end link and removes slack)
• Knocking noise from the front suspension when rocking the vehicle side-to-side by hand with it parked on flat ground
• Visible play or looseness in the end link ball joint when the front wheel is raised and the link is pushed and pulled by hand

What to check

With an assistant rocking the vehicle laterally, listen for knocking from the front end. Check that the sway bar mounting bushes are also in good condition. If a workshop inspection is possible: Raise the front of the vehicle and visually inspect both end links for cracked boots or visible corrosion at the ball pin. Use a pry bar to apply lateral force to each end link and check for movement in the joint beyond the normal rubber compliance.

Symptoms to notice

• Oil weeping or pooling on the rear differential casing or driveshaft boots
• Burning smell from underneath after highway driving
• Gear oil smell noticeable inside or outside the vehicle
• AWD engagement inconsistency or rear wheel slip on low traction

What to check

1. 1.Check the gear oil level via the differential filler plug (should be level with the filler hole).
2. 2.Inspect the rear driveshaft CV boot inboard ends for oil contamination from differential seals.
3. 3.Check the differential casing for any longitudinal cracks from impact damage on vehicles with off-road history.
4. 4.If a workshop inspection is possible: Place the vehicle on a hoist and inspect both left and right rear differential output shaft flanges for oil seeping or wet residue trails.