Car Mechanic - your answers 17/01/2009

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OVERHEATING CHEVY
Q: I have an overheating problem on my 1989 Chevy half ton truck (5.7 litres). It overheats only when I am driving on the road, but not when the engine is just at idle. When I stop the truck and check the hoses and radiator, the top is cold and bottom is hot... I have replaced everything that I believe could relate to the problem, such as the water pump and thermostat. I have also changed the cylinder head gaskets. The radiator and hoses are the only things I haven't yet replaced, although I replaced the radiator last year because I had the same problem. I also replaced the heater core, and have cleaned/flushed out the radiator but the problem still occurs...... very confused here; please can you help? Posted by: Barry

A: It would be worth re-checking the coolant hoses, to ensure that they are not collapsed or otherwise blocked internally. Sometimes as they age, the hoses can become so soft that they 'fold inwards', preventing the flow of coolant. Make sure too that there are no air locks in the cooling system; all the hoses should be warm after the engine has been running for a few miles. When you replaced the radiator, was it a new one? If it was a used radiator, it could be blocked inside, typically in the centre section. Water might still flow through the radiator core 'around the edges' so if, during a test, you run water through the radiator from top to bottom (or vice versa, to 'backflush' the radiator with the unit out of the vehicle), it may appear that the water will flow easily through the core, whereas in fact this may be internally restricted. Making sure that you keep clear of all moving parts, and with the engine stopped after driving for a few miles, feel the radiator core by hand (CAUTION – it may be VERY hot); the temperature should be approximately even between the centre and sides of the radiator core. Cool areas indicate possible internal blockages. You do not mention the engine's cooling fan. Has this been checked for correct operation? An ailing fan will account for overheating of the type you describe. Another possibility is that the coolant passages within the engine may be partially obstructed by limescale and/or other debris. This can also encourage overheating, but flushing the system with a proprietary chemical cleaning agent designed for the job (and available from auto stores) may help. If this doesn't work you will need to seek the assistance of a radiator/cooling system specialist.

KERBING DAMAGE
Q: In slippery conditions I have hit the kerb and damaged my front offside tyre. On trying to fit my spare wheel/tyre I cannot straighten up my wheel as it hits against the side of the wheel arch, also the wheel seems to sit at an angle from top to bottom. Could this be a wishbone problem or might there be further damage? Posted by: Mark

A: Unfortunately it seems very likely that the damage to your car is far more severe than you first thought. Kerbing, even at fairly low speeds, forces major loads through the front tyre and wheel, then through the hub assembly to the steering and suspension components, and then on through the structure of the vehicle. You do not say which make and model of car you drive, but typically damage in incidents like this can affect the wishbone(s), steering drag links and swivels, steering rack and ball joints, spring/shock absorber and their mountings, and quite possibly the 'chassis' or underbody of the vehicle too. For safety reasons, it is imperative that before you attempt to drive the car, you have it very carefully checked by a competent mechanic, to fully assess the extent of the damage. The affected components will need to be renewed, and if the 'chassis'/underbody is twisted, the affected sections need to be straightened or replaced professionally. In all such cases it is essential that the steering alignment is checked after repairs have been carried out. The wheel and tyre will also need to be examined by a specialist, and probably replaced too, alas. Sorry to be the bearer of such sad tidings.

TRACK ROD END REMOVAL
Q: How do I remove a track rod end from the steering rack? Posted by: Simon

A: You do not state the make and model of car you drive, so the following is a 'rule of thumb' method that should help in most cases... With the front of the car jacked and securely supported on axle stands, remove the front wheel on the side you are working on. Locate the locknut on the arm protruding from the steering rack (the locknut will be tight against the track rod end ball joint) and taking great care in case the spanner slips, slacken the lock nut just a little, so that it is no longer touching the inner face of the track rod end ball joint. Now slacken (but don't yet remove) the nut securing the track rod end ball joint to the steering side arm (connected to the steering swivel). If you are intending to re-use the track rod end ball joint, initially don't fully remove its nut, but leave it positioned so that it covers and protects the end of the ball joint pin thread. Now use a purpose-designed 'ball joint separator' tool (obtainable at reasonable cost from a motor accessory/tool outlet) to separate the ball joint from the steering side arm. Once freed from the side arm, the ball joint can now be unscrewed from the steering rack arm.

If the steering rack arm rotates as you attempt to unscrew the ball joint, try GENTLY gripping this arm in the jaws of a self-grip wrench, to prevent it from turning as the ball joint is unscrewed. If you are renewing just the track rod end ball joint, next screw the new joint onto the steering rack arm so that it is in the same position as the original joint, and attach the ball joint to the steering side arm. You may have to gently tap the ball joint against the steering side arm, in order to be able to fully tighten the nut, since the ball pin and its thread may try to rotate as the nut is tightened. (Note: ALWAYS use a new self-locking nut here, unless your car features a castellated nut secured by a split pin, in which case ALWAYS use a new split pin on re-assembly). When the ball joint pin is secure in the steering side arm, re-tighten the locknut on the steering rack arm. If you are removing the track rod end in order to change a split steering rack gaiter, you will also have to remove the locknut from the steering rack arm (the outer, narrow diameter end of the new gaiter will not be large enough to pass over the locknut). Before removing the locknut, precisely mark its position on the threads (using a little white paint, or typists' correction fluid), so that on re-assembly, you can reposition it in its original place on the thread. When fitting a new steering rack gaiter, ensure that the gaiter is fully located on the rack before its securing clips are fastened, and make sure that the gaiter bellows are not over-stretched as the steering is turned from lock to lock. Before fitting/tightening the rack gaiter securing clips, re-lubricate the steering rack with lubricant as recommended by your car's manufacturer. Observe all recommended torque settings on re-assembly (consult your car's workshop manual, or enquire of a dealer). Whenever you disturb the steering in the manner described, ALWAYS have the car's 'tracking' re-checked afterwards by a specialist (garage or tyre fitting specialist), since the steering alignment may have been affected, resulting in rapidly wearing front tyres and sometimes even poor handling.

. CARRY ON DRIVING REGARDLESS?
Q: I drive a 2004 Ford Taurus on which the fan clutch is ailing. Can I still drive it without causing more problems? Posted by: Connie

A: It is always wise to have a problem like this attended to as rapidly as you can, before the component fails, possibly causing damage to other parts too. It's almost always cheaper to have the cause of the problem dealt with as soon as you can, and this will give you peace of mind too that the vehicle will not break down without warning.

FUEL LEAK
Q: I have just noticed that my car is using excessive fuel. I have checked and there is a leak somewhere underneath, towards the back end of the vehicle! Is it safe to drive for a while as I can't afford to have it fixed immediately? Posted by: Russ

A: Unfortunately this is DEFINITELY NOT a problem you can leave to its own devices, even for a short while. Fuel leaks are dangerous, in fact potentially lethal, and you MUST have the leak fixed immediately. The leaking fuel could ignite and result in a serious fire and/or explosion. It could be that the leak is very easy and inexpensive to fix, especially if the cause is simply a loose pipe union (for example). In any event you need to have the car examined by a competent mechanic to find the precise cause of the leak, and to ascertain the cost of repairs. Whatever the cost, you will soon save more than the money spent, due to the cost of the fuel saved.

NO OIL
Q: As I was driving I heard a kind of rumbling noise coming from the front end of my car. I carried out checks on a few things, including the oil level – and I discovered that the sump was empty. So I filled it with Castrol 15w-40 oil. The noise is still there but not as loud as it was. Any pointers would be appreciated; and thanks in advance? Posted by: Amin

A: Oh dear. Sadly, it is very likely that the lack of lubricant has seriously damaged the engine. Effectively, the engine oil is designed to enable metal surfaces to slide against each other, due to the very thin film of lubricant between them, which minimises friction and lowers temperatures. When an engine is run without oil, friction rapidly builds up between the moving metal surfaces, causing localised overheating and damage to the structure of the metal (especially the crankshaft and camshaft bearings, also the piston rings). Ultimately, if the car continues to be driven, the engine will seize solid as the metal components 'weld' themselves together... In your case, you might be lucky and possibly the engine can be restored to good health just by changing the big end bearings (for example). However, the unit will need to be dismantled and examined in order to ascertain the extent of the damage. Modern engines run with smaller oil sump capacities than older units, and in general there is less margin for error than in older cars, in terms of allowing the oil level to run low. In addition, in many cases the oil quality and level directly affect the running of the motor. Dirty oil, or a low oil level, can adversely affect the operation of the engine management control system. When you have had your engine fixed or changed, it would be wise to check the oil level at least once a week in future, or possibly daily if you frequently use your car for long, fast trips (in which oil is consumed at a greater rate than when driving in town). If an engine is consuming oil, it doesn't take very long for the sump to empty and for damage to occur.

POLO TYRE PRESSURES
Q: I have a VW Polo TDI and my handbook gives the tyre pressures as 2.1/2.3 Bar for the front and 2.1/2.6 Bar for the rear. How do I convert Bar to PSI? Thanks for your help.? Posted by: Kenneth

A: To convert Bar to PSI, multiply by 14.50326. So 2.1 Bar equates to 30.46 PSI, 2.3 Bar equals 33.36 PSI, and 2.6 Bar works out as 37.71 PSI. For quick reference in the future, it may be helpful to write the equivalent PSI figures in your handbook, and/or to keep in the vehicle's glovebox a small card on which the above figures are recorded.

CLUNKING ROVER
Q: I own a Rover 75. My problem is that I get a dull clunking sound when I turn the steering wheel just off centre both ways, and the front coil suspension springs jerk a little; or at least this is were the noise seems to come from. I only noticed this after having the car tracked? Posted by: Jennifer

A: It is difficult to be certain, but it sounds as if something may have happened while the car was having its tracking checked/adjusted. Possibilities for the cause of the noise include loose or damaged components, and/or components touching adjacent parts when the steering is moved. In the first instance, take the car back to the garage or specialist where the tracking was carried out, and ask them to re-check the steering rack and its gaiters, also the track rod end ball joint securing nuts; these would have been disturbed if the tracking has been re-adjusted. If you get no joy here, take the car for a second opinion from an independent, competent mechanic. Of course, it could just be coincidence that the noise was only noticed after the car had been tracked. There could be an unrelated problem causing the noise, but in any case this needs to be investigated as it could have safety implications.

REFUELLING DIFFICULTY
Q: I've just bought a 1997 Ford Fiesta; and the petrol tank filler cap is virtually impossible to unlock. Can I get it fixed, and will this be expensive? The car's central locking is also ailing. How much will this cost to repair? Posted by: Ann

A: Fuel cap locks often become difficult to operate as time goes on (in extreme cases the key can even break off...), and in most instances they can be freed quite easily. If you can remove the cap from the vehicle, apply a little water dispellant/lubricant spray (available in aerosol cans with easy-to-direct spouts) to the moving parts of the cap's locking mechanism, and carefully work the key backwards and forwards. Repeat the procedure and within a few minutes the lock should operate much more easily and smoothly. Wipe off excess lubricant from the lock and the key, before re-fitting the cap to the vehicle. If this approach does not bring about any improvement, it would be wise to invest in a replacement filler cap (together with a matching key of course), just in case one day you are unable to remove the original. The cost should only be a few pounds. If you regularly re-apply lubricant in the manner described (say, once a year), the cap should always operate freely.

In addition, there is less chance of moisture entering the moving parts of the lock mechanism and freezing solid in winter conditions. With regard to the faulty central locking system, it is impossible to diagnose the trouble without seeing the car, and of course the cost of repairs will depend on what has actually failed in the system. You will need to take the car to a reliable mechanic to establish the root cause of the problem, then an estimate of the likely cost can be obtained.

. OILY 206
Q: What does it mean when there's thick black oil pouring from the water coolant bottle? I have a 1999 Peugeot 206 1.9 diesel. Posted by: Barbara

A: Unfortunately it sounds as if the cylinder head gasket has 'blown' on your engine, allowing the engine oil to enter the coolant. The problem needs to be rectified immediately before further damage is done (the cylinder head will have to b removed and checked, and the cylinder block face will need to be assessed for warping too). If at all possible, avoid driving the car until it has been fixed. You will need to have the engine checked by a mechanic/garage you can trust, to confirm this diagnosis of a failed cylinder head gasket.

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