Maintenance you might not know about

Many components wear slowly and sit out of sight. They are easy to miss when a car still starts and drives normally. The correct interval and fluid specification vary, so use the logbook and owner’s manual for your exact car.

Driveline fluids

Automatic transmission fluid and filter. This fluid lubricates, cools and helps operate the transmission, while the filter catches wear material. It is often skipped because there may be no simple dipstick and the car can shift normally for a long time. Old or incorrect fluid can contribute to poor lubrication, heat and wear. Follow the specified interval and fluid type. Delayed engagement, harsh or slipping shifts, shuddering, a leak or unusual fluid condition means it needs checking. Our transmission and clutch page covers the workshop side.

CVT fluid. A continuously variable transmission depends on its specified fluid for lubrication and operating pressure. It gets missed when it is treated like an ordinary automatic or described as maintenance-free without checking the actual schedule. Using the wrong fluid or leaving it too long can affect operation and accelerate wear. Check the logbook interval, and act on shuddering, whining, delayed drive or a warning message.

Manual gearbox oil. Gear oil protects the gears and bearings. It can be overlooked because there is no engine-bay dipstick and no regular top-up point. Low or degraded oil can make shifts noisy or difficult and can damage bearings. The service schedule sets the due date; stiffness, crunching, whine or a leak calls for an earlier check.

Differential and transfer case oil. These oils protect gears that divide power between wheels and, on a 4WD, between axles. They are hidden underneath and can be missed in general servicing. Water contamination, low level or worn oil can damage costly gears and bearings. Follow the 4WD schedule, especially after towing or water crossings, and investigate new whining, binding, vibration or leaks.

Brakes and cooling

Brake fluid. It transfers pedal pressure through the hydraulic system and absorbs moisture over time. The reservoir can still look full while the fluid’s protection has declined, which is why a visual level check is not a replacement schedule. Moisture lowers the fluid’s resistance to heat and can promote internal corrosion. Many makers specify replacement every two years, but your logbook controls. A soft pedal, warning light or fluid loss needs immediate attention. Read more about brakes, steering and suspension.

Coolant. Coolant carries heat away and protects the system from corrosion. It gets missed because a full expansion tank can make old coolant look adequate. Its protective additives decline with time, and the wrong mixture can harm the system. Replace it at the stated time or distance, whichever comes first. Overheating, a falling level, coloured drips, a sweet smell or discoloured fluid needs an engine and cooling check. Never open a hot coolant cap.

Belts, filters and plugs

Timing belt. It keeps internal engine parts moving in time. It sits behind covers, so wear is not obvious during a casual look. A snapped belt can badly damage some engines. Replace it at the logbook's kilometre or time interval, whichever comes first, and include related parts specified for the job. Do not wait for noise as a reminder.

Drive belts. These run accessories such as the alternator or air-conditioning compressor. They may be skipped when the visible surface looks sound, even though ribs or tensioners are worn. A failed belt can stop charging or cooling. Cracks, fraying, glazing, squeal or a charging warning calls for inspection, while scheduled replacement depends on the car.

Spark plugs. Petrol engines use them to ignite the mixture. Long replacement intervals make them easy to forget. Worn plugs can cause difficult starting, misfiring, poor running and extra load on ignition parts. Use the exact plug type and interval in the manual. Misfire, hesitation or a flashing check-engine light needs prompt diagnostic testing.

Engine air filter. It keeps dust out of the engine. It may be ignored between services, especially when it is enclosed in a box. A blocked filter can restrict airflow, while a damaged or badly fitted one can admit dirt. Inspect it at the scheduled service, sooner after dusty travel. Poor running or visible contamination can signal attention is due.

Cabin pollen filter. It cleans air entering the cabin. Because it does not directly stop the engine, it is often left in place. A blocked filter reduces airflow and can make demisting and cooling less effective. Replace it on schedule, or when airflow falls, the fan becomes noisy or a stale smell persists. Run the air conditioning regularly through winter to help keep its seals lubricated.

Fuel filter. It traps contamination before fuel reaches the engine, and matters most on diesels. It may be buried underneath or in the engine bay. A restricted filter can cause hard starting, loss of power or fuel-system trouble. Replace or drain it as the logbook specifies and investigate warning messages or poor running.

Electrical and battery

Battery. It supplies the high current needed to start the engine and supports electrical systems. It often receives attention only after a flat start. Heat shortens battery life, and many batteries last around 3 to 5 years, though use and condition vary. Slow cranking, dim lights during starting, corrosion or repeated flat starts mean test it. Charging faults can mimic a failed battery, so an auto electrical check should separate the cause.

Look for the battery’s fitted date if it is recorded, and ask for a test before a long drive when starting has slowed. Some cars require a battery to be registered or configured after replacement. The owner’s manual also explains any precautions for stop-start systems or high-voltage vehicles.

Suspension and wheels

Suspension bushes and shock absorbers. Bushes locate moving parts and shocks control body and wheel movement. Gradual wear can feel normal because you adjust to it. Worn parts can affect control, braking stability and tyre wear. Knocks, bouncing, wandering, fluid on a shock or uneven tyres are reasons to inspect them; the normal service check should also look for play and damage.

Wheel bearings. Bearings let each wheel rotate while supporting the car. They are sealed on many cars and have no routine adjustment, so they can be forgotten. Wear can become noise, looseness or heat and can eventually affect safe wheel operation. A hum or growl that changes with speed or cornering needs checking.

Power steering fluid. Hydraulic systems use fluid to transmit assistance and lubricate the pump. Many newer cars use electric steering and have no fluid at all, so check the owner’s manual to see which system yours has. For a hydraulic system, follow the specified fluid and inspection interval. Heavy steering, pump noise, foaming or a leak needs attention. Do not add a generic fluid without confirming the specification.

Diesel and hybrid

Diesel particulate filter. The filter captures soot and periodically burns it off through regeneration. Cars used mainly for short Annandale trips may not always reach the conditions needed to finish that process. Repeated interruption can load the filter and cause warning messages, reduced power or the need for repair. Follow the owner’s manual instructions for your car and have persistent warnings checked.

Hybrid battery cooling intake or filter. Some hybrids draw cabin air through an intake to cool the high-voltage battery. It can be missed because it may sit near or behind a rear seat. Dust, lint or luggage blocking it can reduce cooling and increase battery temperature. Keep the intake clear and follow the hybrid service schedule for inspection or filter cleaning. Fan noise or a battery-temperature warning needs attention.

Harold Park Repairs services all makes and models. We will never sell you something you don't need. Bring the logbook or service history so we can separate overdue work from items that are not yet due. For checks you can do between services, read the car care guide. Before a holiday drive, use the long-drive checklist.

Questions about often-missed maintenance

How do I know which maintenance schedule applies?

Start with the logbook and owner's manual for your exact car. Read the severe-use notes as well, especially if most driving is short trips, stop-start traffic, towing or dusty travel.

Does automatic transmission fluid last forever?

No. Fluid and filter requirements vary, so use the interval and specification in the logbook or owner's manual. Delayed shifts, shuddering, leaks or unusual fluid condition need investigation.

Why does brake fluid need replacing?

Brake fluid absorbs moisture over time. That reduces its protection and can affect braking under heat, so follow the car's specified replacement interval. Many makers state every two years.

Can short trips affect a diesel particulate filter?

Yes. Repeated short trips may not create the conditions needed for a diesel particulate filter to complete regeneration. Follow the owner's manual and have warning messages or reduced power checked.