Question 1

PCV System Oil Leaks and Breather Box Failures

Accepted Answer

Oil everywhere, particularly around the back of the engine and firewall. You might see smoke at idle or a rough idle. In severe cases, the turbo oil feed line can blow apart because the crankcase is pressurised like a balloon. Volvo's PCV system is baroque. The breather box (flame trap) sits on the back of the block and clogs with sludge over time. When it blocks, crankcase pressure has nowhere to go, so it forces oil past every seal it can find. The turbo cars are especially vulnerable because boost pressure exacerbates the problem. Replace the breather box/flame trap assembly. This is a bastard of a job on turbo cars because access is appalling. Budget half a day and skinned knuckles. The box itself is around $100-150. While you're in there, replace all the associated hoses, they'll be brittle. Check the oil trap in the inlet manifold as well, it's part of the same system and often overlooked. Do this every 100,000 km as preventive maintenance.

Question 2

Timing Belt and Water Pump

Accepted Answer

The engine suddenly stops. If you're lucky, nothing else happens. If you're not, you've just destroyed pistons, valves, and possibly the head. This is an interference engine. The belt is old and tired. The water pump seizes. The tensioner gives up. Take your pick. Replace the timing belt, water pump, tensioner, and all idler pulleys as a package. No exceptions. Use OEM Volvo parts for the water pump, aftermarket pumps fail early. Expect to pay $400-600 in parts if you DIY, double that at a shop. Interval is 100,000 km or 10 years, whichever comes first. If you don't know the service history, do it immediately.

Question 3

Oil Consumption (Turbocharged Models)

Accepted Answer

You're adding a litre of oil every 1000-2000 km. Blue smoke on startup or under boost. Piston ring wear, especially on high-mileage T5s. The 2.3L and 2.4L turbo engines from the mid-1990s can be oil burners. This is often down to extended oil change intervals and poor-quality oil. If it's mild, live with it and check the oil obsessively. Severe cases need a bottom-end rebuild or engine replacement. Forged pistons and upgraded rings will sort it permanently but that's a full build, not a repair. Expect $3000+ for a proper engine rebuild.

Question 4

Turbo Failure (T5 and 850R)

Accepted Answer

Loss of power, screaming noises, oily exhaust smoke. The car feels gutless and the boost gauge stays flat. Oil starvation from a blocked PCV system, failed turbo oil feed or return lines, or just age and heat cycles. The factory Mitsubishi TD04 turbos are tough, but 200,000+ km and poor oil changes will finish them. Replace or rebuild the turbo. A rebuilt unit is $800-1200. Upgraded options like a Garrett GT30 or GT35 are popular if you're going down the modification route. Always replace the oil feed and return lines, they're cheap insurance. Check the PCV system at the same time.

Question 5

Radiator and Expansion Tank Cracks

Accepted Answer

Coolant loss, overheating, the temperature gauge climbing past 12 o'clock. You might see pink coolant pooling under the car or steam from the bonnet. Plastic ages badly. The radiator end tanks crack, the expansion tank splits, hoses perish. It's just time and heat cycles. Replace the radiator if the end tanks are cracked (common on 200k+ km cars). Expect $250-400 for an OEM-quality radiator. Replace the expansion tank every 5 years as preventive maintenance ($50-80). While you're at it, do all the coolant hoses, especially the ones near the turbo, they bake and go brittle.

Question 6

Cooling Fan Failures

Accepted Answer

The temperature gauge climbs in traffic or at idle. The radiator fan doesn't spin up when it should. Failed fan relay, temperature sensor, or the fan motor itself has died. On 850s, there are multiple temperature sensors and it's often the one for the fan circuit, not the gauge. Test the fan by jumping the relay or running 12V directly to the motor. If the motor works, replace the relay ($20-40) or temperature sensor ($40-80). If the motor is dead, replace the fan assembly ($150-250). You can wire a manual override switch as a temporary fix, but it's not a long-term solution.

Question 7

Heater Core Leaks

Accepted Answer

Sweet smell in the cabin, fogged-up windscreen, wet passenger footwell. Coolant loss with no visible external leak. The heater core has corroded through. Replacing the heater core means removing the entire dashboard. This is a 10-12 hour job and absolute hell. Budget $200-300 for the part and $1000+ in labour if you're not doing it yourself. Some people bypass the heater core and live without cabin heat, which is fine if you're in Queensland but less clever in Tasmania.

Question 8

Fuel Pump Failures

Accepted Answer

The car cranks but won't start, or it starts then dies. You might hear the fuel pump whining or buzzing loudly, or complete silence from the tank when you turn the ignition on. Age and heat. The in-tank pump eventually gives up. Poor fuel quality doesn't help. Replace the fuel pump. Drop the tank (or cut an access hatch in the boot floor, which is common). OEM pump is around $200-300. If you're running a modified turbo car, upgrade to a Walbro 255 ($150) or Bosch 044 external pump. Check the fuel pump relay in the fusebox as well, it's a common failure point.

Question 9

Fuel Pressure Regulator Leaks

Accepted Answer

Fuel smell in the cabin or engine bay. Poor idle, hard starting. You might see fuel leaking from the regulator on the fuel rail. The diaphragm inside the regulator perishes. Replace the fuel pressure regulator. It's on the fuel rail, easy to access. $100-150 for the part, 30 minutes to fit.

Question 10

Alternator Failures

Accepted Answer

Battery light on, dimming headlights, dead battery after a short drive. You might hear a grinding or squealing noise from the alternator. Worn brushes, failed voltage regulator, or seized bearings. High-mileage cars eat alternators. Replace or rebuild the alternator. Rebuilt units are $200-300, new OEM is $400+. If you're running big stereos or auxiliary lights, upgrade the wiring from the alternator to the battery, factory wiring is marginal.

Question 11

Central Locking Pump Failures

Accepted Answer

Central locking works intermittently or not at all. You hear a buzzing or grinding from behind the rear side trim. The vacuum pump for the central locking system fails. It's a known weak point. Replace the pump. It's behind the left rear interior trim panel. $150-250 for the part. Some people delete the system entirely and fit aftermarket central locking, which is more reliable.

Question 12

Dashboard Mounting Tab Failures

Accepted Answer

Creaks and rattles from the dashboard. In severe cases, the dash shifts or sags. The plastic mounting tabs on the back of the dashboard crack and break. This is common on all 850s and early V70s. Remove the dashboard (it's involved, see the detailed guides in the forums) and repair the tabs with metal straps or "piping strap" as reinforcement. Use self-tapping screws and cover with felt tape to prevent squeaks. This is a weekend job. If the tabs are completely gone, you'll need a new dash or a used one.

Question 13

ETM (Electronic Throttle Module) Issues

Accepted Answer

Surging idle, erratic revs, engine stalling, poor throttle response. You might get fault codes 1610, 1604, 1614. The car may refuse to start or only start after multiple attempts. The ETM gets dirty or the throttle position sensor fails. This is less common than forums suggest, but when it happens it's a pain. Clean the throttle body thoroughly with carb cleaner. Check all the electrical connections and clean them with contact cleaner. If that doesn't fix it, replace the throttle body gasket (it can cause air leaks). Worst case, replace the ETM ($300-500). Do not ignore fault codes, clear them and see if they return.

Question 14

Automatic Transmission Failures (AW50/51)

Accepted Answer

Harsh shifts, slipping between gears, no movement in drive or reverse. The transmission might overheat and go into limp mode. The AW50/51 gearbox in 850s is not strong. It doesn't tolerate abuse, high power, or neglected fluid changes. The torque converter can fail, valve bodies clog, and clutches burn out. Service the transmission fluid every 50,000 km. Volvo claims it's "lifetime fluid", they mean the lifetime of the transmission, which will be short if you don't change it. Use genuine Volvo ATF. Fluid and filter change is $200-300. If the box is slipping, you're looking at a rebuild ($2000-3000) or replacement ($1500 for a used unit).

Question 15

Manual Gearbox (M59) Whine and Bearing Failures

Accepted Answer

Whining or grinding noises in certain gears, difficulty shifting, or the gearbox jumps out of gear. Worn bearings, synchros, or low/contaminated gearbox oil. The M59 and M58 are generally strong, but 200k+ km takes its toll. Change the gearbox oil (often overlooked). Use 75W-90 synthetic. If the damage is done, you'll need a rebuild or replacement gearbox. Rebuilds are $1000-1500, used boxes $500-800.

Question 16

Driveshaft (Propshaft) Issues on AWD Models

Accepted Answer

Vibration, clunking, or banging from underneath, especially on acceleration or deceleration. The centre support bearing fails, or the driveshaft itself is damaged. AWD 850s are rare, but this is a known issue. Replace the centre bearing or the entire driveshaft. Expect $300-500 in parts. Check the rear differential mounts at the same time.

Question 17

Front Control Arm Bushings and Ball Joints

Accepted Answer

Clunking over bumps, wandering steering, uneven tyre wear. You might feel the steering wheel shimmy or the car pull to one side. Rubber bushings perish, ball joints wear out. Standard consumables on a 25-year-old car. Replace the front lower control arms as complete assemblies, it's easier than pressing out bushings. Genuine Volvo arms are $150-200 each, aftermarket Lemförder or Meyle are $80-120. Do both sides. Ball joints can be replaced separately if you're keen, but it's fiddly. Also inspect the front subframe bushings and consider IPD's polyurethane inserts ($70) for sharper handling.

Question 18

Steering Rack Leaks

Accepted Answer

Power steering fluid leaking from the rack, heavy or notchy steering, whining from the pump. Rack seals fail. The pump can also fail, but the rack is more common. Replace the steering rack ($400-600 for a rebuilt unit) or rebuild it yourself if you're brave. Check the power steering pump and hoses as well. Fluid leaks are annoying but rarely leave you stranded. Top up the fluid and plan the repair.

Question 19

Strut Top Mount Failures

Accepted Answer

Clunking or knocking from the front suspension, especially over bumps or when turning. You might notice excessive camber or tyre wear. The rubber bearing in the strut top mount deteriorates and the strut starts moving around. Replace the strut top mounts (also called strut mount bearings). These are $50-80 each. If the struts are old, replace them at the same time. Bilstein or Koni are good upgrades from the standard Sachs units.

Question 20

ABS Pump and Module Failures

Accepted Answer

ABS light on, no ABS function. You might hear grinding or buzzing from the ABS unit under the bonnet. The ABS pump motor fails or the module itself dies. This is common on high-mileage 850s. Replace or rebuild the ABS unit. Rebuilds are available from specialists ($300-500). A used unit is $150-300. The car is still safe to drive without ABS, but you won't have it in an emergency.

Question 21

Brake Master Cylinder Leaks

Accepted Answer

Soft or spongy brake pedal, brake fluid loss. The pedal might sink to the floor under sustained pressure. Internal seals in the master cylinder fail. Replace the master cylinder ($150-250). Bleed the entire system afterwards. Check the brake servo (vacuum booster) at the same time, if it's failed, the pedal will be rock-hard instead of soft.

Question 22

Rear Wheel Arches and Sills

Accepted Answer

Rust bubbles, holes, or structural rot in the rear wheel arches, sills, and inner arches. Water and salt sit in the arches. The drain holes block. Poor undercoating or stone chips expose bare metal. Cut out the rust and weld in new metal. This is panel beater territory unless you're handy with a welder. Expect $500-1500 per side depending on severity. Prevention is key: wash the underside regularly, clear the drain holes, and apply a decent rust inhibitor like Waxoyl or Fluid Film annually.

Question 23

Tailgate Rust (Wagons)

Accepted Answer

Rust along the bottom edge of the tailgate, especially around the number plate lights and lower corners. Water sits in the tailgate frame and rots it from the inside out. Cut and weld, or replace the tailgate. Used tailgates are cheap ($100-200), but check them carefully, they all rust in the same spots.

Question 24

Subframe Corrosion

Accepted Answer

The rear subframe (where the trailing arms mount) rusts through. This is catastrophic if it lets go. Salt and water sit on the subframe. Australian cars are generally okay, but northern European and North American cars can be shocking. Inspect it carefully. If it's rotten, replace the subframe or weld in repair sections. This is a big job. If you're buying an 850, check the subframe before you hand over money.

Question 25

Heater Blower Fan Failures

Accepted Answer

No air from the vents, or the fan only works on certain speeds. The blower motor fails or the resistor pack dies. Replace the blower motor ($100-150) or the resistor ($40-60). The motor is behind the glovebox. It's a 30-minute job.

Question 26

Window Regulator and Motor Failures

Accepted Answer

Windows move slowly, make grinding noises, or stop working altogether. The window regulator or motor wears out. Replace the regulator or motor. Genuine Volvo parts are $150-250 per window. Aftermarket units are cheaper but fail sooner. The door cards come off easily (four screws and some clips).

850 / 850 T-5R / 850R

850 / 850 T-5R / 850R known problems