UNDERBONNET CHECKS

1 TOP-UP SCREENWASH

Lift the blue cap for the reservoir and extract the filter inside the neck of the filler. Wash it under a cold tap if there’s dirt inside, then refit. Top-up the screenwash with the appropriate solution (not washing-up liquid).

2 CHECK COOLANT LEVEL

The translucent coolant reservoir should be clean enough on the outside to be able to see the level inside. There are MIN and MAX markers on the side to help check the level. Top-up with G13-rated coolant, which should be changed every five or six years.

3 CHECK BRAKE FLUID LEVEL

Shine a torch on the side of the brake fluid reservoir. The level should be up to the MAX marker on the side of the reservoir. Top-up with DOT 4 fluid (VW 501.14), or whatever has been used before. The brake fluid should be refreshed every two years.

4 CHECK AUX BELT

The ribbed auxiliary drive belt can be partially inspected from above the engine bay, but also after the engine undertray has been removed (see step 21). Look for cracks across the ribs and fraying.

5 SQUEEZE HOSES

Providing the engine and its coolant are cold, squeeze any coolant hoses in the engine bay to look for perishing and damage. Check all coolant hoses are secure and look for signs of leaks (pink residue).

6 CHECK BATTERY

Check the 12V battery voltage with a multimeter or battery tester. Make sure the terminals are securely fitted and not corroded – apply a smear of petroleum jelly to them. Check the battery is securely located.

7 FUSEBOX LID REMOVAL

There’s a small fusebox next to the battery. Release the plastic clips for its lid to look inside and see if there is any corrosion or damp. If any of the fuses need to be replaced, there should be a small plastic tool on the underside of the fusebox’s lid to help with removing them.

8 GREASE BONNET RELEASE

Spray grease over the locking mechanism for the bonnet (on the top of the slam panel). Apply a little grease to all the door locks and hinges (including the tailgate). Operate them several times to work the grease inside.

9 REMOVE DIRT AND LEAVES

Look in the rear corners of the engine bay for dirt and debris that can block any nearby drainage holes and channels. Clean any dirt away and pour a little hot water down the drain channels to ensure the water runs out below.

10 REMOVE HOUSING

The air filter is contained inside a plastic housing on the top of the engine. Detach two induction hoses, which may be secured with spring clips that can be difficult to compress without the correct tool shown here. Detach any breather hoses to remove the housing.

11 RELEASE THE LID

Turn the air filter housing upside down and undo two crosshead screws. The screws cannot be extracted but need to be fully undone. Release the four plastic clips around the edges of the air filter housing and its lid should separate from it.

12 REPLACE AIR FILTER

After releasing the lid of the air filter housing, extract the old air filter, clean inside and then fit a new air filter, making sure the holes for the securing screws line up correctly. Reassemble the housing and refit it onto the engine. This can be awkward to do.

13 ADD ENGINE FLUSH

Once all the engine bay checks have been conducted, the next stage is to drain the oil, but if you wish to add an engine flush, this can be done now and left for a few minutes with the engine running to take effect. The one shown here needs the engine to be run for 15 minutes – do not drive the vehicle.

14 CHECK LIGHTS

Whilst the engine is idling with an engine flush and its old oil circulating, there should be time to complete a few exterior checks. For instance, check all the exterior lighting. Most headlight bulbs can be accessed from inside the engine bay and most rear light bulbs from inside the boot.

15 CHECK TYRE TREADS

Inspect the condition of the tyres, looking for damage around the sidewalls (both sides). Check the depth of the tread is at least 1.6mm across 75% of the tyre where tread wear indicators are present between the tread blocks.

16 CHECK RIMS

Look around the edges of the rims of the wheels for kerb damage and buckling. Check the inside edge of the wheels where a buckled wheel can easily be missed. When the wheels are on the ground, make sure the wheel bolts are tightened to 120Nm, unless you intend to remove them to service the brakes.

17 MEASURE DISCS

Use a Vernier caliper or similar tool to measure the thickness of the brake discs – there should be enough space to do this without having to remove the road wheels. The minimum thickness for a front ventilated disc is 22mm, whereas a rear solid disc is 7mm.

18 CHECK PAD THICKNESS

Use a brake pad gauge to measure the thickness of the pads’ friction material. There should be enough room to manoeuvre this into position without having to remove the road wheel, although it may help to turn the steering to full lock when checking the fronts.

19 CHECK FUEL CAP SEAL

Release the fuel filler flap and unscrew the fuel filler cap. Check the condition of its rubber seal, looking for signs of perishing – it must be replaced if it’s damaged because petrol fumes may leak out and if spotted at the MOT test, it will fail.

20 CHECK WIPERS

Inspect the condition of the windscreen wipers and the rear wiper, looking for cracks and splits in the rubber that makes contact with the glass. Operate the screen washers and wipers to check they move smoothly across the glass and don’t smear or drag.

21 REMOVE UNDERTRAY

The engine undertray is secured with nine Torx T20 screws that will probably be rusty, so spray over them with penetrating fluid before attempting to undo them – clean their heads with a small brush to avoid rounding them off.

22 DRAIN OIL

Position a drain bowl or similar container underneath the sump, then undo the 19mm drain bolt. There should be four litres of oil to collect, so leave it for a few minutes to drain and in the meantime…

23 REMOVE OIL FILTER

…use an oil filter wrench/strap to undo the spin-on oil filter at the front underside of the engine. Some oil will drip out when removing it, so have a container at the ready to collect it – the oil filter will be partly full of old oil.

24 RENEW OIL DRAIN PLUG

Fit a new oil drain plug and tighten it to 30Nm. Wipe up any oil that may have leaked around the sump – this will help to determine whether there are any oil leaks from the engine in the future.

25 FIT NEW OIL FILTER

Check the new oil filter is the same size as the old one, then add a smear of fresh oil to its seal to help reduce the risk of it grabbing and tearing. Fit the new oil filter and only tighten it by hand (officially, it should be tightened to 20Nm).

26 FOUR LITRES OF 502/504

Pour four litres of 502/504-grade 5W-30 oil (grades vary according to climate) into the top of the engine. A funnel or adaptor (as shown here) can help because the filler neck on the top of the camshaft cover is very awkward to access, so oil can easily spill over. Afterwards, run the engine to check the oil pressure light goes out, check for leaks, switch off, check the level on the dipstick and top-up if required.

27 EXTRACT OLD FILTER

The cabin filter is accessed via the passenger footwell. Look underneath the glovebox for an oblong plastic panel. Move two plastic sliders into the middle of it and the panel should fall down to reveal the bottom edge of the cabin filter. Pull it out.

28 CHECK AIRFLOW ARROWS

Look for any airflow arrows on the side of the new cabin filter. They should point towards the middle of the vehicle when the filter is fitted. Remove any leaves and debris from where the old cabin filter was fitted, then fit the new filter.

29 REFIT PANEL

Carefully refit the oblong-shaped plastic panel that was removed in step 27, ensuring the short front edge is nearer to the back of the vehicle. Move the two plastic sliders outwards to help lock the panel in position.

30 CHECK FRONT ARMS

The front suspension consists of lower arms, so visually inspect the outer balljoint and use a pry bar to lever against it to check for excessive movement. The balljoint can be replaced separate to the lower arm and costs around £20 for a new one.

31 CHECK INNER BUSHES

Use a pry bar to check for excessive movement in the two inner mounts for each front lower suspension arm. A new arm costs around £50 (without a new balljoint). Look for corrosion in the arm and its mounting points on the subframe.

32 SQUEEZE BOOTS

Pinch the rubber gaiters on the ends of the driveshafts (both ends) to look for cracks and the risk of grease escaping, with water and dirt getting inside. Make sure each gaiter is securely fitted with suitable clips.

33 WIGGLE DROPLINKS

Shake the droplinks and the ends of the front anti-roll bar to feel for excessive movement, which can result in a knocking noise when driving. A replacement droplink costs around £20 and mounting bushes for the ARB cost around £15 for a pair.

34 CHECK TRE BOOTS

Pinch the rubber dust covers around the ends of the steering track rod ends to look for cracks and perishing that could let dirt and water inside and result in premature wear. Check the corrugated rubber gaiters on the ends of the steering rack in the same manner.

35 CHECK DOGBONE MOUNT

Use a pry bar to check for excessive movement in the lower gearbox mount shown here. It’s secured between the gearbox and subframe. If its bushes are worn, this could result in engine movement during acceleration or braking. A replacement costs around £30.

36 CHECK EXHAUST MOUNTS

Working from the front to the back of the vehicle, inspect the condition of all the rubber mounts (hangers) for the exhaust system, looking for splits in the rubber and signs of perishing.

37 CHECK EXHAUST CLAMP

Mark at AES says that the exhaust clamp shown here, which is in the centre of the exhaust system, can corrode, resulting in leaks. A replacement costs around £15 and can be fitted in situ, although the exhaust does need to be separated where the clamp is fitted.

38 CHECK REAR SPRINGS

The rear coil springs can be visually inspected from underneath the rear of the vehicle.

Look for fractured coils, but do not touch the springs in case you trap your fingers. Carefully brush any dirt away from around the base of each spring.

39 INSPECT DAMPERS

Look at the rear telescopic dampers for leaks and corrosion. Use a pry bar to check the bottom mounting bush for excessive movement, which could result in a knocking noise at the rear when driving the vehicle.

40

TRAILING ARM BUSHES

Use a pry bar to lever against the frontmost bush that locates the beam axle at the rear of the Polo. Visually inspect the bush for perishing. Excessive movement in the bush can result in uneven tyre wear and handling issues. A new bush costs around £15.

41 INSPECT BRAKE PIPES

Look for the brake pipes routed across the rear beam axle and to the front of the vehicle. Check them for corrosion and clean any dirt from them. Protect them with a smear of grease.

42

WIGGLE WHEELS

Wiggle a raised road wheel from top-to-bottom and from side-to-side to check for play in the suspension bushes and steering (front only). Rotate the rear wheels with the handbrake off to listen for a worn wheel bearing.