Car clinic: a rusty Yeti, a flat fob and an expensive flywheel

The car clinic experts

TIM’LL FIX IT
Tim Shallcross used to train AA patrols to fix cars. Now he advises the Institute of Advanced Motorists.

INSPECTOR GADGET
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory.

Q. My three-year-old Skoda Yeti has spots of rust at the bottom of its front doors. Although it has mud flaps, the rust seems to have been caused by stone chips  and, I believe, poor-quality paintwork. Do I have a claim against Skoda for this (incidentally the car is just two weeks out of warranty), and how should I repair the damage, given that I plan to sell the car in a year?

TW, Usk, Monmouthshire

A. Although Skoda guarantees the paintwork of all its new cars for 12 years, this only covers rust originating from the inside, rather than external corrosion caused by scratches and chips, so the damage you’re concerned with will not be covered.

You need to treat all of the chips ‒ no matter how small ‒ as soon as possible to prevent them growing. For shallower paint chips where the metal is not yet visible, a dab of touch-up paint should be enough. You can get touch-up paint from your Skoda dealer or car-accessory shops such as Halfords, and prices range from £10-£20, depending on the brand.

Manufacturers give their paint colours very specific names, and you can find yours written in your service book and often in the boot too, usually under the carpet in the vicinity of the spare-wheel well.

For areas of bare metal that have begun to rust, it is best to apply a rust inhibitor such as Hammerite Rust Remover Gel (£5.49 for 100ml, halfords.com) before the touch-up paint. As the name suggests, it comes as a gel that is applied with a small brush, and it stops the rust from getting a hold and continuing to spread beneath the paintwork. It may be visible to buyers who look closely, but at least it is not as obvious or as off-putting as rust.

DP

Q. I recently left my Land Rover Freelander unused for five weeks ‒ apparently long enough for the batteries of my two key fobs to go flat. Luckily, I was able to open the car with the old-fashioned mechanical key. Why don’t the makers provide some sort of mains or USB charger, as is usually the case with other electronic devices?

PH, London

A. Your Freelander comes with a sealed fob powered by a capacitor rather than a conventional battery. The capacitor stores the electrical charge required for the fob to send a signal to lock or unlock the doors and arm the engine immobiliser. The fob is recharged automatically from the car’s electrics each time it is inserted to start the car.

Because a capacitor does not hold its charge for as long as a battery, the manufacturers advise owners to alternate the use of their main and spare fobs. Although it takes 30 minutes to fully recharge the fob, just a few minutes on charge is sufficient to open the doors of the car.

The main advantage of this sort of key ‒ and the reason it is  becoming increasingly common  ‒ is that it’s lighter and cheaper to produce. And where rechargeable batteries have a limited lifespan, a capacitor does not, and can last the lifetime of the vehicle.

DP

Q. My son has been told by his car dealer that it will cost £1,257 to have the dual-mass flywheel of his 2007 Audi A3 2.0 TDI replaced. A local garage, however, has quoted him £918. How many drivers do you think know that such costly jobs are needed?

MG, Newcastle-under-Lyme

A. Dual-mass flywheels (DMFs) are a consequence of the rising popularity of diesel (and in some cases petrol) cars that are frugal yet powerful.

An engine flywheel smooths out the unpleasant “thumping” caused by the pistons moving up and down. Without one these pulses make it difficult for the engine to idle (tick over) at the low speed we’re used to, and they are transmitted to the car’s wheels via the clutch and gearbox, so accelerating their wear.

In the past a flywheel was just a heavy iron disc bolted to the end of the crankshaft and carrying the clutch assembly, and it would typically last for the life of the vehicle.

But as modern engines wring ever-increasing amounts of power from as little fuel as possible, the force of the “explosions” in the cylinders keeps increasing, necessitating ever heavier flywheels to maintain smooth crankshaft rotation.

The heavier the flywheel, the slower an engine’s throttle response, and that’s where the altogether lighter DMF comes in. It comprises two flywheel discs — one bolted to the crankshaft, the other to the clutch — connected by a cushioning device incorporating  a number of springs, which weaken over time.

Because of this, many DMFs need to be renewed every 50,000-70,000 miles, and as that is typically the mileage at which the clutch wears out, it’s best to renew the clutch at the same time.

The other drawback with DMFs is that any misfire or abnormal imbalance of the compression and combustion forces can wear out the flywheel more quickly. If your DMF fails earlier than expected, get the car checked out for an underlying cause.

TS

Got a car problem?

Email your question to carclinic@sunday-times.co.uk, or write to Car Clinic, Driving, The Sunday Times, 3 Thomas More Square, London E98 1ST, with a daytime phone number, your address and as much detail about your car as possible. We can’t reply personally, so please don’t send original documents or SAEs. Advice is offered without legal responsibility.