BE­FORE START­ING

Car Mechanics (UK) - - Servicing from Home -

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.

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