What do engine service parts do?

If you're a Master Mechanic then this article is probably not for you. However, if you are looking for some clarity as to what those engine service parts you have just bought, or been charged by the garage to fit actually do, then read on...

Everything on a vehicle has an expected lifespan. Some items like a radiator hose are 'fit and forget' - you only change them if they stop performing the task that is required of them, in the case of a coolant hose, if it splits and starts leaking. Other items such as spark plugs, engine oil or an air filter, for example, are considered engine service items which should be routinely renewed to ensure optimum running of your engine. Ignoring these service schedules can lead to poor performance, possible breakdown and at worst potential long term damage or component failure.

A number of components are key to an engine that will wear out with use. Typically the manufacturer will suggest these are replaced every 12,000 miles or 12 months. Check your owner's manual to find out the specifics of your vehicle.  Presuming you drive an older petrol-powered car your oil and filter will need to be replaced, and your air filter, fuel filter, distributor cap and rotor arm will also want to change. If you have points ignition (unlikely on cars made after 1990) then these will definitely need swapping out for a fresh set. For slightly newer cars or vans add a pollen or cabin filter to your service shopping list too. The good news is we do an extensive range of engine service kits with most of what you need in one handy box.

Whilst you have the bonnet up and your overalls on there are a few other things to cast an eye over. For water-cooled vehicles check the level and condition of your coolant/anti-freeze and for all models, you should top up your brake fluid (if required) with an expectation that it is changed every 4 years unless you are using silicon-based fluid DOT 5. We've discussed brake fluid in more detail here. The same goes for Power Assisted Steering fluid - give quick glance to check all is fine, but consider a flush and freshen up every ten years or so. Lastly, for petrol vehicles, give the HT leads a bit of a wiggle, if they are feeling stiff it could be sensible to swap them out for a new set.

We'll keep this brief, as it could soon turn into a pre-MOT check and that is a more in-depth subject. Tyres, quite simply have they got tread and the right amount of air in them? Brakes, check your discs don't have a big lip on them and that there is still some meat left on the pads. Wiper blades and fluid - this is probably the item motorists are most aware of, so are likely to be in a good useable condition. Give your exhaust a quick wobble and listen for noises, any banging could indicate a broken rubber hanger, stick your head under the bumper for added peace of mind. Bulbs - these have a habit of failing at inopportune moments, so while you're in the fixing mindset run through a quick test and switch out any faulty items, we sell bulbs and bulb kits if required.

Engine Oil is used to keep the moving parts of your engine lubricated and rotating smoothly. It also aids with reducing engine operating temperatures. As oil gets older its properties change and its lubrication and cooling work become less effective. A late oil change is unlikely to kill your car, but it could play a part in limiting the life of your engine. Oil is a golden colour when fresh out of the can, so check your dipstick and if it's black you will know its time to change. In short, changing the engine oil will involve draining the sump, removing the oil filter renewing it and then refilling the oil. Let a small amount of new oil run through the sump before refitting the sump plug, to help clear out any sediment in the bottom of the pan. You'll need a suitable container to catch the old engine oil in (an empty oil can with the side cut open is a cheap fix for this) - you'll also need a solid container to empty this into, to then safely dispose of the waste oil at a later date.

Regardless of whether you drive a Petrol or a Diesel, there are a few important things required to make your engine work: Fuel and Air (and a spark for petrol models). The air filter ensures that no dust particles or dirt enter into the internals of your engine via the intake system. A small speck of dirt might seem insignificant on the tip of your finger, but in the confines of your combustion chamber could cause damage to a valve, piston or the cylinder head. The air filter is typically placed in a plastic or metal housing and is usually made from a fine weave paper, allowing fresh air to pass through it but trapping dirt. Over time the filter becomes dirtier, making it harder for clean air to pass through which can then affect the performance of your car and its economy. It is worth noting that some aircooled models had an oil bath air filter, which simply requires cleaning out and refilling. if you have a cotton or foam-based performance air filter or induction kit fitted these can be removed, washed out and then re-oiled, making them good for another year of motoring.

Fuel from the pump is clean, so you may be wondering why a fuel filter is important. The main reason is not contaminated fuel, but to trap dirt and rust floating inside the fuel tank and pipes. Older vehicles suffer from corrosion on the inside of their metal fuel tank, which as well as causing small pieces of rust to partially block your pipes, could also gain access to your pump, carburettor or injectors and eventually the combustion chamber if it wasn't for a fuel filter. The most simple of inline fuel filters, like the type you'd find on a Beetle or early Golf just fit in line with the fuel pipe coming from the tank and are installed as a safety measure before the fuel pump. Generally, they are clear plastic cylinders, so it is evident when these get dirty as the yellow filter turns darker and the sediment sits in the bottom of it. On vehicles with fuel injection fitted (including Diesel), a metal canister fuel filter is used.  You cannot see inside these - but trust us it will be a similar story, especially if they have been in place a few years.

Unlike the other two filters above, the pollen filter or cabin filter is for you, rather than for the engine. But just like the engine air filter (and they look pretty similar in most cases) it catches any nasties in the atmosphere and stops them from being sucked into your ventilation system. Before cabin filters came along, you turned on your heater or blowers and bits of leaf and other debris were fired out at speed towards your face! Of course, the ventilation system will also benefit from being clean and not clogged up with atmospheric dirt too.

You won't necessarily need to change your spark plugs every time you carry out a service, but it would be prudent to give them a check. Wet or dry, different colours, can give you a key insight as to what is happening inside your engine. For those unsure, spark plugs are only fitted on petrol-powered vehicles and as the name suggests, provide a spark into the combustion chamber at precisely the right moment to create the 'bang' which in turn powers the car or bus. The spark plugs are connected by HT (High Tension) Leads to the distributor. The distributor is connected to the coil, which generates the spark. The timing of the spark is controlled by the points (if fitted) and assigned between each cylinder by the rotor arm which spins inside the distributor, making a connection with each HT lead many times a second.

We'd suggest you only tackle tasks on your vehicle which you feel comfortable with doing, or that you have more than enough time to teach yourself to do. Before opening up your toolbox consider what could break and the effect that might have on your vehicle, or your life, for example, if you use the vehicle every day. Engine servicing is relatively straight forward, but that isn't to say things don't go wrong. When removing anything that is threaded there is an outside chance of the thread stripping; this could happen with the sump drain plug or a spark plug. If it feels like it is stuck, it might be best to leave that bit to a professional. Likewise, take care when refitting threaded components. Wind them back in by hand, before then using a socket or spanner to tighten to help avoid cross-threading. In the case of spark plugs, a small amount of copper grease on the threads will assist with removal next year.

If you are removing your HT Leads, either do them one at a time or mark and/or photograph the order in which they are fitted. If you get these round the wrong way your 'firing order' will be out of sync and you'll have dreadful running issues if the vehicle even starts at all! Another good tip is to double-check all the engine servicing parts you have ordered before the 'big day' so should there be any concerns over fitment, you have time to sort it.

Hopefully, you have found this guide useful? And even if it hasn't got you rolling up your sleeves to tackle these jobs yourself, you might have learnt a little more about what engine service parts do. Keen to learn more? Drop us a comment below with your suggestions and we'll look into them for a future feature.

Andy