Ask a mechanic - 01/03/06

A: We're not aware of any engine differences; on the 220 GTI the cam belt should be checked every 24,000 miles and replaced at 48,000 miles. If you're not sure of the previous service history, renew the belt immediately. NONE-TOO CRANKY
Q: My year-2000 Mitsubishi Shogun automatic sometimes won't turn over without a jump-start from another car. The battery has been renewed and the charging system seems fine. I've also noticed there's a one-second delay between turning the key and the engine cranking.
Posted by: *Bertram*

A: It's most likely a dodgy starter motor. Check the current-draw while the motor cranks - if excessive the starter circuit needs going over minutely. This fault may be due to a poor connection or to a dead spot on the starter-motor commutator.

OLD MONTY IN HIDING
Q: When I started using my 1988 Montego 1.6 on unleaded fuel I noticed the fuel consumption increasing. I thought I'd get the engine tuned, but I've been told there's no point because this engine isn't compatible with unleaded petrol. Is that right?
Posted by: Seedmeister

A: Yes. We can't imagine where your Montego has been for the last several years, but you could instead use unleaded petrol together with a protective additive such as Millers VSP. Your engine won't need any alteration to its settings.

KNOCK KNOCK, WHAT'S UP?
Q: My Ford Fiesta makes a knock from the near-side front corner when I either back-off or reapply the accelerator, and also when mounting the driveway. It's only a slight noise, but annoying enough. What could it be?
Posted by: ether

A: It might be caused by a driveshaft joint, especially if more noticeable with full lock applied. It could also be down to one of a number of joints in the suspension and steering systems; possibilities include: lower suspension ball joint, track rod end, steering rack end bush, suspension strut top mounting, anti-roll bar joint. Take your pick!

AIRBAG CONCERNS
Q: Twice recently the airbag warning light of our Mazda came on while driving. The first time the dealer just reset the system, but the second time they replaced a sensor. A second dealer checked the original sensor but couldn't find fault, so I'm now worried that Mazda might be fitting an unreliable sensor - have you come across this?
Posted by: milaud_stephen

A: It's not a known Mazda fault, but as with any warning light problem, it needs to be followed up. We recommend a visit to another main dealer or an independent auto-electrician for a full check.

DON'T BE PARANOID!
Q: I have always changed the oil and filter on my new cars at the first 1500 miles. In October I bought a nearly-new Nissan Micra and its mileage is now 2500. It hasn't had that early oil change, so should I change the oil and filter immediately?
Posted by: drunkenstein

A: You should not need to change the oil and filter any sooner than the manufacturer recommends. Car makers used to specify a first oil change at around 1500 miles but that's no longer necessary as modern oils are so good, as indeed are modern engine build tolerances. Don't worry, just follow the service schedule.

ALL DOWN TO TIMING
Q: My 2002 Renault Scenic 1.9 dCi always returned 50mpg - until it came back from its 72,000-mile service, since when it has been consistently 8-10mpg worse. Why would this be?
Posted by: MurgatroydRex

A: It appears something was done incorrectly at service time, and it's down to the servicing garage to find out what. One possibility is that they renewed the camshaft belt (specified at this mileage) and got the valve timing wrong when fitting the new belt.

DON'T BE SO SILLY
Q: Could you tell me if it's okay to fit 205/55 tyres to the 7Jx16 rims of my VW Bora V5 rather than the standard 6.5J rims? If it is okay to do this, what would you expect the effect on handling to be?
Posted by: jamesbatch40

A: We're not going to recommended it. It's unlikely that roadholding or handling would be noticeably improved, and this deviation from the standard fitting would have undesirable repercussions in terms of your insurance cover. It's not worth doing, so forget it.

(ALMOST) CLEAN AS A WHISTLE
Q: Would I be right in saying that a modern diesel such as the Peugeot 407, which is fitted with a particulate trap in the exhaust, has the cleanest emissions of any new car?
Posted by: Istanbullah

A: A diesel like the 407 is among the cleanest cars, but still produces fairly high levels of oxides of nitrogen - more so than modern petrol cars. In terms of carbon dioxide, hydrocarbons, carbon monoxide and particulates though, it is pretty unbeatable.

TWEAK THOSE CABLES
Q: The second gear of my VW Bora's 6-speed gearbox has become notchy and sometimes baulky to engage. It has always been notchy from cold but now it's like it when hot too. Is there some sort of adjustment?
Posted by: Bilbo

A: Adjustment of the Bora's two gearchange cables is possible and might be beneficial. It's also worth checking the clutch is clearing properly and that you have the right oil in the gearbox.

SOMETHING FISHY GOING ON
Q: My wife's Toyota Corolla is two years old and has done 20,000 miles. At a recent service we were told the rear tyres had only 1.5mm of tread left, while both fronts were 'as new'. How can this be?
Posted by: peter_royle

A: As this is a front-wheel-drive car it is inconceivable that the front tyres would exhibit no wear after 20,000 miles and that the rears would be very worn - they should still be in good shape. It sounds as though someone has swapped the fronts for the rears... but who?!

CONFLICTING INFORMATION
Q: Could you tell me at what mileage I am supposed to change the camshaft drive belt of my 1994 Rover Metro 1.1? I have been given conflicting information about this.
Posted by: MrMaddox

A: The Rover recommendation is for the belt to be renewed every five years or 60,000 miles, whichever comes first, but the previous service history, and the current condition of the belt, should be taken into account.

ROUGH RIDER
Q: When I slow down in my 1999 Golf TDI 110 at below 20mph, and when braking, the engine idles really roughly, as if it's running on three cylinders. When I release the brake pedal it idles normally again; why?
Posted by: trailblazer

A: It's an odd one, but possibly because brake application increases the load on the vacuum pump that drives the brake servo. This would suggest a fault with the engine management system, which may still be delivering fuel when it should cut off. Get a VW electronic diagnostic check done.

TURNING THE AIR BLUE
Q: My 1997 Citroen Saxo 1.6 has done 115,000 miles and has started producing blue smoke from the exhaust, though only when started up or after idling a while at traffic lights. What would cause this?
Posted by: byte*me

A: It sounds as if there's a problem with the valve stem seals and/or valve guides. Oil is being drawn down past the valve seals when the engine is idling, and is then burned when driving off. Get a mechanic to investigate it properly.

A THIRSTY FORD
Q: I've recently bought a petrol-powered Ford Focus C-Max and its fuel consumption is astonishingly poor, at about 24mpg around town. As this is nowhere near the official consumption figure, should the dealer do something about it?
Posted by: lainey

A: The dealer should at least investigate. But you haven't told us the engine capacity, or whether you have automatic transmission; it's possible the 2-litre engine with an automatic would normally return this sort of consumption.

WHY DRIVE DIESEL?
Q: Please could you explain the advantages and disadvantages of running a diesel car? I change my car every two years but have so far always chosen petrol models.
Posted by: shadowdancer

A: The advantages include 30-40% greater fuel economy, better torque characteristics (more driving flexibility), longer gearing for more relaxed cruising and greater engine longevity, better reliability, lower toxic exhaust emissions overall. Disadvantages these days only amount to more noticeable tickover noise from outside, and sometimes a heftier initial price tag.

A CURE FOR NOTCHY SHIFTS
Q: Both of our family cars - a Citroen ZX and a Nissan X-Trail - have a notchy gearchange, so I'm wondering if it would be okay to use an additive to the transmission oil, such as Molyslip or Slick50. Would that improve the gearchange quality?
Posted by: sandwichman

A: These oil friction modifiers might well help ease the notchiness of gearchanges, and they are safe to use. However, if the cars are under warranty, check first with the manufacturers that the use of additives won't jeopardise a claim.

next page

Did we answer your question? If not submit one now