Do your research on which jobs are required by the official service schedule, which you should find in your handbook. Also, consult DIY manuals, online forums and back issues of CM for any vehicle-specific tasks. Carryout all jobs as described in any weekly checks, including topping-up the screenwash, inspecting the driving controls and seatbelts, plus checking that all lamps operate.
Remove any engine covers carefully – research how they attach and do not simply yank at them. Store them safely. Note if any of them are equipped with vibration dampers and evaluate if they need to be replaced. Some plastic covers can be very brittle, so research how they come off before resorting to brute force.
After the car has been standing overnight, check the tyre pressures and inspect beneath the car and within the engine compartment for any leaks emanating from hoses, or seals. Coloured crystalline deposits, such as those pictured, indicate a potential coolant leak. A level check should be mandatory (see Step 16).
Check the fuel injector’s electrical connections are in good order and inspect the feed and return pipes for leaks. Should you notice a tar-type deposit building at the injector base on modern direct-injection diesel engines, consult a fuel injection specialist for advice, because extra remedial work may be necessary.
It is not that easy to inspect drivebelts in detail without removing them, especially if they are short and wrap around many pulleys. Renew the belt if you can see any indication of either perishing on its ribbed running surface, or splits developing on the top, which indicate that the belt is starting to delaminate.
Spark plugs are best renewed with a cold engine. Some engines might have plugs powered by high-tension (HT) leads, which simply pull off the end of the plug, but be careful as they can corrode and be stubborn to separate. Do not yank on the lead, as it might break. Hold the lead as pictured – by its connector.
Using a dedicated socket with a rubber insert to grip the plug body, unscrew the spark plug anticlockwise and note its condition (see Step 8). Certain engine layouts (ie, smart cars, some Renault V6 models, etc) make accessing spark plugs very difficult. The plug body is made from ceramic and can snap on removal, so take care.
Worn spark plugs increase fuel consumption and place a strain on other parts of the ignition system. You can tell a lot about the engine’s condition by the spark plug’s nose deposits. Most workshop manuals go into detail about this, but a light grey colour, as pictured, is a good sign. Unlike old cars, modern vehicle electronics tend to warn you if anything serious is awry, by illuminating the engine management lamp.
Renew the spark plug by checking with a feeler gauge that its gap is correct. The specification tends to be given in the workshop manual; a new plug’s factory-set gap might be on the packaging. Adjust it by bending the top electrode, not the centre one. This advice does not apply if you fit a multi-electrode plug. To reduce the chance of seizure, it may be beneficial to place a light coat of copper grease on the plug threads (unless not recommended by the plug manufacturer). Winding in the plug finger-tight will reduce the chance of cross-threading, prior to tightening with a suitably-sized socket, or torque wrench. Once the new part has been tightened to its correct torque, repeat Steps 7-10 on the remaining spark plugs. Check the HT lead ends for corrosion. Running the engine at night and seeing a blue flash will indicate that the leads are ‘leaking’ and need replacing. Look especially where they might touch the engine, or each other.
Power is fed to the spark plugs via the HT leads from the distributor. Remove the distributor cap, turn it over and ensure that the central spring-loaded carbon contact is in good order. Do not mix up the order of the HT leads, if you either disconnect or replace them (see Steps 6 & 13).
Check that the outer contacts are neither burnt nor short-circuiting against each other – a thin black line (called ‘tracking’) between the contacts shows the direction in which current is bypassing the intended route. Pull off the rotor arm and ensure that the end contact on its nose is not pitted (see inset pic). Renew the parts if you are unsure.
Should your car be equipped with an electro-mechanical distributor, check that the coil is in good order – two different designs are pictured. All you need to do is ensure that all wires going to and from it are in good condition. Be wary of the extremely high currents – the ignition should always be switched off.
On many newer models, the separate distributor and coil is replaced by a single unit. Some cars may have one coil per spark plug, others might possess a single unit that is bolted to the cylinderhead. Lifting it away reveals the spark plugs beneath (one cam cover has been removed on this engine for clarity).
Unscrew the coolant expansion tank and not only verify that the level is correct but that the antifreeze concentration is between 30% and 50%. The pictured hydrometer is an inexpensive but useful tool. While colour should not be used to identify the different types, brown coolant indicates that it needs changing – black (and/or an oily or white deposit) could indicate a more serious mechanical problem.
Should it be time for coolant renewal, you can run a flushing agent through the system, which will help dissolve scale and break-down rust deposits. However, this will involve running the engine to its normal operating temperature, thus allowing it to circulate. Follow any supplied instructions carefully and let the engine cool afterwards.
Coolant should be drained, when warm, or cool, by either removing the bottom hose from the radiator, or unscrewing any drain tap. If your car lacks a convenient drain tap (as shown above), slowly remove the expansion tank cap before disconnecting the bottom radiator hose. Never drain hot coolant, as it can boil and scald you when the pressure cap is released. Close the tap, or refit the bottom hose. Look for any perishing/splitting of the rubber hoses. Open any bleed screws (see inset pic) and pour in either pre-mixed coolant, or mix antifreeze with deionised water in equal amounts. Ensure that you close the screws, when you see coolant emerging – consult your workshop manual for details on bleeding the system. With the level correct (as pictured), switch off the aircon and turn the heater to its hottest setting, then start the engine. Open the bleed screws to purge the system of air. Wait until the engine's thermostat opens and coolant flows through the radiator. Open and close the bleed screws until no more air bubbles emerge. Run the engine until the electric cooling fan turns on and off, while monitoring the temperature gauge.