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Towcar maintenance


In this series of towcar maintenance tutorials to be published over the next few months, we address the most important issues associated with looking after your vehicle. Last month’s Technical Talk dealt with the wheel bearings on your caravan or trailer. Now we move on to nurturing your towcar, because without it, there would be no towing holiday to enjoy! Sure, you can use a trusted vehicle service agent, particularly if your vehicle is a late model. But owners who are fairly capable handypersons and drive older towcars that are out of warranty needn’t go to this expense. Much of the work can be carried out efficiently and reliably by you! This month we focus on engine servicing, comprising the oil change, oil, fuel and air filter changes, and spark plug replacement. Next time we’ll tackle the brakes and running gear (wheels, tyres and suspension), and finally we’ll see to the steering and transmission.

Engine service

Without an engine all you have parked in your garage is a heap of scrap metal. Your engine needs basic tender loving care, every 10 000 km if it’s a diesel and every 20 000 km if it’s a petrol engine. If you’re doing your own servicing, you can afford to stick to these intervals. The diesel fuel in South Africa is very high in sulphur. Unless you consistently buy the more expensive 50 ppm (parts per million) grade, your oil will be quite degraded by 10 000 km – and, no matter what the manual says, clean oil at regular intervals will certainly prolong your engine life.
In other words, you need to ensure that your engine breathes clean air, that it consumes only clean fuel and that its lifeblood is kept clean and pure. You also need to give it a total ‘blood transfusion’ at regular intervals. So, let’s begin …

Oil and oil filters

Take a drive of about five kilometres to warm up your engine (warm oil drains out better than cold oil). Don’t go too far as you don’t want it too hot; hot oil can cause severe burns. Park your vehicle on a level spot and put the ignition keys somewhere safe and far away. (You don’t want to absent-mindedly start your engine until you’re finished!) Place several sheets of newspaper under the engine to protect the floor, and then position your metal tray on the newspaper and below the sump plug. (If you don’t know what this is, stop now and make an appointment at your nearest trustworthy service centre.) Loosen the sump plug (but don’t remove it just yet), position your tray to catch the imminent flow of warm engine oil, then give the sump plug a final turn, grabbing it just before it falls into the tray – this will be followed by a cascade of warm engine oil. Keep your hands clear! If the plug falls into the tray you can retrieve it later.
Wait five minutes while all the oil drains out of your engine. If you are a purist you will now proceed to jack up various wheels to do maintenance work on the brakes and wheels. The changing angles of the car ensure that you drain every last dreg of the old, grimy oil.

Now remove the oil filter: This is either a cylindrical spin-off cartridge about 100 mm in diameter and between 100 mm and 150 mm long which is screwed onto a housing against the engine block, or a housing with a screw-on cover with the actual filter element inside. Some engine designers take great delight in making the filter as inaccessible as possible, so that you need rubber wrists with superhuman strength to get to it. Clean off all dirt where the filter or cover meets the housing, then unscrew the filter. That means turn it anti-clockwise away from the mounting point.

With the spin-off cartridge-type you may find that it’s so tight that you can’t turn it. There are special spanners available from auto-spares suppliers which make this a bit easier. Some are okay, and some are junk; unfortunately you generally can’t make this distinction until you use them. I just use my hammer and punch my screwdriver right through the old filter, then pull on the screwdriver to loosen (but you’ll definitely require newspaper on the floor in this instance, as it’s a messy method).
Discard the old cartridge filter or, if it’s one of those with a cover, remove the filter element and discard.
Smear clean oil onto the rubber seal on the new cartridge filter and screw it into place, as tight as you can make it by hand. (Purists fill the filter with new oil first, thus reducing the time the engine will run without lubrication.)
For the other type, insert the filter into the housing and carefully replace the cover. (Pour in some clean oil if you wish.)
If you can remember where you put your keys, start the engine and run it for about two minutes. Switch off and check at the sump plug and oil filter for leaks. Tighten if necessary. Wait another two minutes, now check the oil level using the dipstick. Top up to no higher than the upper mark on the dipstick. Always wait for the additional oil to settle down to the sump before you re-check the dipstick.
Never, ever overfill, as this can cause engine damage. Replace and tighten the sump plug. Fill the engine with the correct quantity and grade of new oil – check your service manual for these facts. You do this by pouring in the required volume through the filler cap located on top of the engine tappet cover. (‘Where’s the tappet cover?’ Okay, off to your service station!) Replace the filler cap once you’ve poured in the required amount of oil. Finally If you can remember where you put your keys, start the engine and run it for about two minutes. Switch off and check at the sump plug and oil filter for leaks. Tighten if necessary. Wait another two minutes, now check the oil level using the dipstick. Top up to no higher than the upper mark on the dipstick. Always wait for the additional oil to settle down to the sump before you re-check the dipstick.
Never, ever overfill, as this can cause engine damage.

AIR FILTER This is inside a big black housing to one side or the other of the engine. Sometimes it’s right on top of the engine. As most engines these days use a pleated paper air filter, that is what I will describe.
The housing will have a cover or lid of some sort, held on by means of toggle clamps. Clean all loose dirt from the housing and loosen the clamps. Depending on the layout, you may also have to loosen the circular clips around the flexible rubber duct connecting the filter housing to the intake manifold. Watch out for any little pipes connected to the housing or inlet manifold. If you have to remove any, take careful note of which ones go where.
Take off the cover and remove the dirty filter. Don’t let any dirt fall into the ‘clean’ area of the housing, or into the intake manifold. Wipe (or vacuum) any dirt from the housing. Fit the new filter, close and secure the cover and all clips, hoses and fasteners.

Fuel filter (petrol)

Safety first! Petrol is highly flammable. Do not smoke or use any naked flames while you do this task. Switch off the engine and remove your keys from the ignition.
Look for the housing or component that looks like the fuel filter, or which will accommodate the filter you bought. You’ll find this on the fuel feed line to the engine, under the bonnet. Quite simply, clean off all external dirt, undo any hose clamps or cover screws and replace the filter. For in-line filters, ensure that you get the flow direction right, usually indicated by an arrow on the housing.
Start your car and check for any fuel leaks.

Fuel filter (diesel)

Switch off and remove your keys from the ignition.
Because the injector pump operates at very small clearances, and the fuel is more viscous, diesel filters are bigger and more sophisticated than petrol ones. You may even have two of them in series: one to remove moisture and one for dirt.
Thoroughly clean the housings before you begin. Sometimes the filter bowls screw off just like the spin-off cartridge-type oil filter mentioned earlier; sometimes they are secured by a centre bolt, or are under a cover. Just analyse the task and work at it logically. If you’re at all unsure, rather get professional advice or assistance.
Fit the new filter or filters. Now you have to bleed the air out of the filters, otherwise the injector pump will cavitate and not deliver to the injectors. The user manual may indicate where to find the bleed screw, otherwise look for a prominent screw, with a drain port, adjacent to it, somewhere on the filter housing. It may even have a convenient short length of hose attached to it. Run the hose into an empty jam tin, if there is space, or connect an extension to it and down to a tin on the floor.
Loosen the bleed screw one full turn. Switch on the ignition but DO NOT START the engine. You will hear the fuel delivery pump running, somewhere near the fuel tank. Wait at the bleed screw until fuel flows cleanly from the hose, then close the bleed screw. Remove the jam tin and dispose of the fuel.
On later model engines you merely have to depress a button on the top of the filter housing with the ignition on and this purges any air back to the fuel tank.
Now start the engine. If it doesn’t start after a couple of tries, repeat the bleeding exercise. Check for any fuel leaks.


The most important thing here is not to mix up where the high-tension (HT) leads go, especially on a six- or eight-cylinder engine. Identify them by tagging each with a piece of masking tape, then pull the rubber caps off the spark plugs. Be careful not to pull on the lead as it can break out of the end cap quite easily – then you’ll have to buy a replacement.
If your engine is dirty and there’s dirt around the bases of the spark plugs, clean this away as best you can with a small paintbrush. A household vacuum cleaner with a small nozzle attachment also works very well.
Now, using your plug spanner (of the correct size for your spark plugs), remove all the spark plugs and place them on your workbench, oriented as they are in the engine, and examine them. They should all be a brownish colour and oil-free.
If they are black and sooty, your engine is running too rich and you are wasting fuel. If they are all a very light grey, your engine may be running too lean. (These observations are especially applicable to older, carburettor-aspirated engines.) If they are black and oily, either your piston rings or your valve stem seals are worn. Both require specialist attention, which is beyond the scope of this write-up. If only one or two are black and oily, then it’s likely that there’s a broken piston ring on that cylinder, and because you kept them in order, you now know which cylinder it is.
Now that you’ve disposed of this engine diagnostic opportunity, set the electrode gap on all your new spark plugs to the measurement specified in your user manual. The new gap is usually just a little too big, and you need to gently tap the electrode to close it, until your feeler gauge just drags through the gap. If you overdo it and need to open the gap again, use your long-nose pliers and bend the electrode open from its root. Never use your feeler gauge as a lever for this, as you will stress the enamel surrounding the central electrode, potentially cracking it in the process.
Fit the new spark plugs and tighten only moderately. Be very careful not to cross-thread them as this is a very expensive mistake that may entail having the cylinder head removed. You don’t want to go there. Replace the HT leads and you’re ready to roll.


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