Tim Shallcross

Email Tim with your questions

Hi Tim,

Is it possible for Diesel Particulate Filters to get clogged up completely? Do “Regenerations”, as the manufacturers call it, always clear the filters? And if regenerations don’t completely clear the filters, how often am I supposed to go to a service centre and get it flushed? I recently had a problem when I took my 10 month old car in for a service and was told that my DPF was going to need replacing to the tune of £1000 because it was, in their words, “99% blocked”. After challenging them on the point that I had performed the regeneration procedure properly they backed down and said they would flush out the filter at a slight more palatable price of £170. Have I uncovered a scam whereby service centres are charging people thousands instead of hundreds?

Your help would be appreciated.

David Greenberg, UK

To answer your questions in order:

1) Yes, after several interrupted regenerations, DPF “loading”, or getting clogged up, can reach 95%. Then the filter can’t be regenerated – emptied of soot – and needs replacing.

2) Only if they don’t need additive, and provided regeneration is carried out properly and isn’t interrupted before it’s complete. Some manufacturers use an additive to help regeneration, especially on smaller engines where the exhaust temperature may not be high enough to burn the soot – Peugeot and Citroen use it extensively, Volvo do on smaller engines, but check the handbook or ask a dealer if in doubt. If they do use additive, the DPF will typically need changing at around a 60K to 80K service interval.

3) If they’re not properly regenerated, they’ll eventually need “forced regeneration” in a garage – a warning light on the dash will show “engine fault” or somesuch. This forced regeneration is probably what the garage did. However, if you really did carry out the regeneration procedure properly it shouldn’t have needed forced regeneration, so I suspect there were a few instances of the regeneration being stopped before it was complete, which is an easy mistake to make.

4) You’ve probably uncovered some pretty typical ignorance on the part of the garage, but a rip off is certainly possible.

As a general comment, if you live in a city, do a lot of short journeys and rarely get out of town, a diesel car with a particulate filter (DPF) isn’t really for you – and all diesel cars will have the filter soon, to meet the latest Euro emissions regulations, so do ask before you buy. A small petrol car or petrol hybrid will be much better.

Meriva 1.3 CDTi (2007)

I am part of a group of five other people trying to deal with the same problem, we all have or have had Meriva 1.3 CDTI (2007) models of Vauxhall, we have all suffered catastrophic engine damage as a result of malfunctioning Diesel Particulate Filters.

We have exhausted the complaint procedure at Vauxhall - who are still refusing to admit there is a problem with the diesel particulate filters and will not contribute to repairs required (probably because they do not work - after forking out for a new engine our problem was not rectified and we decided to scrap the car - obviously at significant cost to us).

I am willing to act as conduit for the other five Meriva Drivers who are trying to bring Vauxhall to justice over this, but we are struggling.

It would be helpful if we could get in touch with as many Meriva Owners as possible to highlight this problem - NO lights illuminate to alert drivers of the imminent Diesel Particulate Filter Malfunction, and when it does malfuction, the engine is damaged beyond repair.

VOSA are disinterested in pursuing an investigation in to this problem as they say GM report that they have sold millions of these cars and have not had any complaints! Many thanks for any help you can offer. We have been down the usual routes of VOSA, SMMT and trading standards.

Many thanks

Angela Clarke, Stockton-on-Tees, UK

A fundamental question needs to be answered before you go any further. What has led you (and the other owners) to conclude that the cause of engine failure was the DPF? If you’re relying on what the garage told you, I’d get it checked, because although there are one or two web sites that allege that the filter can cause engine damage if it gets blocked, they are very vague and contain no information about exactly what happens and what damage is caused. I can’t find any serious engineering paper on DPF technology that mentions major engine damage as a possibility. The garage trade is notorious for blaming the latest bit of technology for a fault, when the truth is that the garage or the mechanic hasn’t actually got a clue what happened – and in many cases they don’t have a very good grasp of the technology they’re blaming. The fact is, the filter is fitted in the exhaust pipe to filter out soot. If the inside breaks up, it simply lets the exhaust gas escape unfiltered. If it gets blocked with soot, it makes it harder for the engine to push the exhaust gas out, which will give severe lack of power and eventually make the engine impossible to start, but I can’t for the life of me think what permanent damage that might do. (In fact, lots of lorries are fitted with an exhaust brake – an auxiliary brake that shuts a valve in the exhaust, to block it and thereby make the engine hard to turn, giving extra engine braking. That’s exactly the same effect as a blocked DPF. But open the valve - or clean the filter - and everything’s back to normal.)

So, why might the DPF get the blame for the engine blowing up? Well in many cases, an engine that has a serious mechanical problem will be burning its own engine oil in the brief period leading up the point where it all goes bang and stops. Clouds of burnt engine oil in the exhaust will very quickly clog up a particulate filter - it’s only supposed to mop up light traces of soot. Therefore, when a garage dismantles a blown engine, it’s quite likely they’ll find a very sooty DPF – but it’s the effect of the engine problem, not the cause of it.

So, given the track record of the trade in general – and Vauxhall dealers in particular – on accurate diagnosis, I wouldn’t bet my shirt on the DPF being the cause of the blown engines without some other corroboration. Since you’ve now scrapped the car it’s going to be difficult to confirm the actual fault that you had, but assuming the other owners still have their cars, perhaps your first step should be to club together to get a proper engineer’s report to establish the cause of failure of one of them. And if the engineer does find the DPF was the cause, do tell me – if I’m wrong, I’d love to know, and find out exactly what happens.

Hello Tim.

I have a Nissan Tino Almera 1.8 SE+ and it has 63,000 on the clock.

When you drive it the engine is running beautifully and smooth, but when you put the accelerator pedal down it starts to what I would accompany to hop a little, like a little sputter, maybe a misfire, like its spluttering, maybe its fuel starvation, but when you reach 50+ miles an hour the symptoms go away and the car drives normally which makes me think it isn’t fuel starvation. The engine runs really sweet and it ticks over very nicely when it is idling.

Can you help please?

Kind regards

Verina Horner, Hartleypool

Oh if only this was 1979 and not 2009! Things were so easy to diagnose then. All you needed was a chap in navy overalls with a spanner in his hand. “Ah, flat spot. Carburettor, I’ll be bound. It’ll be done in a jiffy.” Some tweaking and serious spanner clanking would be followed by that trick of revving the engine from under the bonnet, using the special “mechanics only” thingy that you could never find afterwards. You’d nod knowledgeably while he explained about keeping the “dash pot” topped up, then you’d be on your way while he wiped his hands on some cotton waste and lit his pipe.

Sadly, neither cars nor nostalgia are what they used to be and the fault could be many things, such as the throttle potentiometer, dirty injectors, dirty spark plugs or coil breaking down. The good news is that none of these is too serious or expensive to cure. If you want to eliminate the simple things before entrusting your wallet to a garage, first take the spark plugs out. Either clean and adjust them, or if they look fairly grotty, fit new ones. Have a good look at all the thin vacuum pipes (3 to 8 mm or thereabouts) going from the engine to the various little valves, sensors and actuators that are filling up the spare bonnet space. Make sure the pipes are connected tightly to something at both ends and not split anywhere along their length. Then try a couple of tanks of an advanced fuel such as BP Ultimate or Shell V Power – I know I keep recommending this, but they do contain very powerful detergents that will clean the entire injection system of old fuel deposits and it does cure lots of problems with hesitation. If you’ve done all this and the fault’s still there, it’s into a garage I’m afraid.

Hello Tim

I have a Morris Minor (1958) 1000 that is off the road which I would like to sell. I'd be grateful if you could tell me the best way to go about this (or how to make a start).

Kind regards

Eileen Allen, UK

Selling it as it is will be simplest, but that will also be the lowest price. If you can get an MOT on it without too much trouble, it’ll help to sell it and certainly increase the price, but don’t get involved in major repairs or restoration – you won’t get it back in the sale price. As a guide, if bodywork looks in good condition, the brakes work and the engine starts, it’s worth getting it to your local MOT garage for a test (or ask them if they’ll come and pick it up). If it needs anything more than the odd light bulb or tyre to pass the test, don’t get involved.

The classic car magazines are quite popular with prospective buyers, but adverts may be quite expensive. There’s a dedicated website at: www.morrisminorsforsale.com/ which doesn’t seem too expensive for ads, but don’t be misled by the prices on there – they’re asking prices, not what the cars actually sell for. Of course, there’s always e-bay if you need a quick sale, and in fact that’s also a useful way of setting your expectations as to what price you’re likely to get. “Watch” a few Minors in similar condition to yours that are advertised on e-bay, then look at the actual sale price once the auction’s ended – realistically, it’s the price you should expect to get. And a couple of words of caution. First, don’t be overly hopeful of getting a top price. There are a few stories around at the moment about people putting money into classic cars because they don’t trust banks, property etc. However, my experience is that when money’s tight all round, prospective buyers of classics know it and they’re looking for real bargains. The second note of caution is the usual list of caveats about selling any car – make sure cheques clear before parting with the car, accompany prospective buyers on any test drive, if they can’t produce proper insurance and a valid driving licence, don’t let them test drive it at all etc etc.

Hi Tim, We purchased a year old Mazda 5 last year which had done 18k and its now at 25k, a few times I noticed that the rear wheels used to angle outwards at the road/drive and inwards into the top of the wheel arches, all it really carries is a small child pram, Seats 6 and 7 in the boot are used very rarely maybe once a month for a short school run distance for a couple of 4year olds.

Anyway I noticed some oil like substance on the road/drive, checked the brake fluid was fine, then thought it must be from the rear shock asorbers, checked with the supermarket it was purchased from, who said common problem take it to Mazda, which we did and they have agreed it is and we are getting both rears done under warranty, but I have now noticed that both rear tyres and well done on the inside edges, spoke to a couple of tyre firms who agreed, the shocks being worn would do this. What's the chances of getting a couple of new rubbers for the rear, bearing in mind the tyres are pretty good apart from the inside edges?

Thanks and keep up the good work

Gavin, Glasgow

The tyres are wearing like this because the suspension has been set up by the manufacturer with negative camber – it helps road holding. The down side is that it increases tyre wear on the inside shoulder, just as you describe. The back shock absorbers don’t affect camber on the Mazda 5, worn or not, so replacing the tyres is down to you I’m afraid.

Hi Tim, I have had a Focus C-Max diesel from new. Once a year we camp for a week and the car is static for most of the week but we do open and shut the doors regularly during the day to store all manner of things. I switch off all the internal lights but there is no a switch for the boot light which comes on on opening. The youngsters are not permitted to have the radio on or use portable DVD off the car battery. I also lock the car regularly but do not trigger the second stage of movement sensors. Inevitably, when I come to use the car at the end of the week, the battery is dead. This has happened with the battery new or up to three years old. Is there anything I can do to keep enough charge in the battery other than an un-eco, unnecessary journey to recharge the battery every two days or so? I can only assume that modern batteries are there to do little more than start the car and replace the charge when moving.

Paul Marsh, UK

On the contrary. A modern battery should be easily capable of starting the car after a week – even with the lights coming on when the door’s opened. I suspect there is a current drain from the battery when you think everything’s switched off. An auto electrician will do a “quiescent current” check, or if you have an ammeter it’s quite simple to do yourself. Ammeters come in two types – the traditional sort which you connect into an electrical circuit in series, or an inductive type that simply clips onto the battery cable. If you can get clip on inductive type, open the bonnet, then check that everything is switched off, lock the car doors and clip the ammeter to either of the battery cables (the thick, heavy duty ones) – positive or earth, it doesn’t matter which, but get as close to the battery terminal as you can. The reading should be less than .05 amps. If it’s higher than that, something is still switched on – either something unseen, like a courtesy mirror light, or because something’s faulty. If there’s nothing obvious left on, remove and replace each fuse one by one while someone watches the reading on the meter. When you remove the fuse from the circuit with the problem, the reading will drop to close to zero amps.

If there’s no undue current drain, and the problem really is excess opening of doors, take the boot light bulb out and consider a solar charger. Or use a bit of Heath Robinson designing to rig up a bicycle powered alternator and get the youngsters to earn DVD privileges by battery charging pedalling sessions...

Dear Tim,

This year (starting October) I intend to garage my Jaguar 'S' Type Twin Turbo Diesel and not use it for 6 months.

How should I prepare the car so that on my return it will function without problems? Should the battery be disconected or not? What else should be done?

I find your input to other questions posed very helpful.

Kind Regards,

Colin Williams, France

How on earth can you contemplate not driving such a great car for six months? Is it a spell behind bars? A vow of abstinence? If so, have you considered celibacy instead?

If you insist on going through with this act of self deprivation, don’t disconnect the battery or you may give yourself some mysterious problems when you come back. If it’s definitely for six months and not significantly more, here’s what you should do, most of which is general advice that applies to any modern car. (Some drivers may find this very finicky, but that’s because they haven’t got a Jag!)

1) Go for a decent drive (at least half an hour in daylight) to make sure the battery’s fully charged. While you’re out, fill the tank with diesel (this will help to stop any water condensing on the tank walls and getting into the fuel while you’re away)

2) Check the anti freeze strength and top up/replace as necessary.

3) Fill the windscreen washer bottle with a 50:50 mixture of water and a good quality screenwash. Spray the washers for about 10 seconds to get the 50:50 mix into the spray jets.

4) Wash the car, then polish it (assuming you haven’t had one of Jaguar’s fancy paintwork treatments). Make sure the carpets are dry, and no damp coats or umbrellas are left in the boot. If the seats are leather, treat them with a leather feed.

5) Park the car so that you can get to the battery on your return (under the boot floor).

6) If the garage is secure enough to leave the car unlocked, leave the windows slightly open. (Don’t do this if you do have to lock the car, otherwise the burglar alarm will keep going off)

7) If the car has the manual handbrake, chock the wheels and leave it off. (This will be virtually impossible if it’s the later electronic park brake, so see the bit about when you return)

8) Lift the wipers off the windscreen (this can be difficult on later S Types because you can’t simply lift the arms, so if necessary just put clean paper underneath the wiper blades)

9) Inflate the tyres to the correct pressure.

10) Modern cars are full of computers with memories that are best kept alive, so I wouldn’t disconnect the battery. Double check that everything is turned off before you leave the car, and take the keys out of the ignition. If you can arrange for someone to look in on the car from time to time, they could start the engine and run it for twenty minutes or so (with the garage doors open). If this can be done once a month as a minimum it will be very helpful. Alternatively, a solar charger can help keep the battery topped up if there’s a convenient window near the car. If no visit or charging is possible, the battery should retain enough charge to keep all the computer memories alive while you’re away, but it will probably not have enough juice left in it to start the engine on your return, so it’s best not to try. Which brings us to:

What to do when you come back:

1) Take the bits of paper from under the wipers.

2) If you didn’t find a friend to start the car once a month, don’t even attempt to start the engine now, otherwise you could drop the battery voltage below that needed to keep the memories energised. Get a good battery charger and charge the battery overnight on the car. Alternatively, connect jump leads from another car to the battery (provided you remembered to leave the car with the boot accessible!). To do this, both cars should be switched off, and it helps to have both sets of keys in your pocket – the central locking can operate when the leads connect and you don’t want the keys inside the car if it does! Only connect three clips to the battery terminals – connect both positives together, then connect the black lead to one battery negative, and the other end to a sound bit of unpainted metal on the other car (the engine is ideal, but well away from the battery. Batteries give off hydrogen and the last connection will create a spark – hydrogen and sparks are not good together).

3) Run the other car at about 1500 rpm for about 20 - 25 minutes (make sure you’re well ventilated)

4) Switch the other car off and disconnect the leads – the one away from the battery must be the first to disconnect.

5) Start your car.

6) If it has the electronic handbrake, release it, then roll the car backwards and forwards to make sure it’s not stuck. If it’s reluctant to roll, try driving it backwards and forwards a few inches.

7) Drive a few yards to get to about 10 mph, then gently apply the brakes to get all the surface rust off them.

8) Go for a good long drive to warm everything up, blow away the cobwebs, and remind yourself of the pleasure you’ve been missing!

Tim, can you please help with this query?

I have a 2003 VW Polo GT TDI. This has the 1.9 twin pump turbo diesel engine and according to my local dealer is quite rare. It's a great car - quick, reliable and economical averaging 55 mpg BUT has a problem with excessive tyre wear on the front (195/55 R15 on alloy rims).

So far I've tried Dunlop SP Sport and Continental Conti Premium Sport 2 tyres but although wear is even across the tread and the car tracks straight and true, I only get about 12-14000 miles out of them. Most of my journeys are around town with the occasional motorway trip so don't think it is anything to do with driving style and the garage which services it tell me there is nothing wrong with the suspension. Having owned many cars over the previous 30 years I have never had to replace tyres before they'd covered at least 20000 miles, so at about £200 each time it's proving to be very expensive.

Is this a problem on all Polos or just this model? Can you suggest another make of tyre with a longer life?

Many thanks for Car Clinic which is a great column.

Richard Duff, Ilkley, UK

Your car has the 130 bhp PD engine. It’s quick and reliable and can be economical – but it’s a very big lump for the Polo, which makes it quite heavy on the front end. That coupled with the fun of using all that torque is often a rubber burning combination. However, to be fair to you, if you’re getting 55 mpg round town you’re not burning rubber away from the traffic lights, and the problem is down to the tyres having to wrench that heavy front end round lots of corners and roundabouts. Sporty cars will wear the driving tyres in particular – talk to Audi A4 owners! However, although you can get harder wearing tyres, they may not solve your problem. The trouble with a harder wearing tyre is that the rubber compound’s harder, which grips the road less. The result may be wheels that are more likely to spin, especially with all the torque they’re trying to transmit to the road, which in turn will wear the tyre more anyway. Shop around for a lower priced decent tyre – Vriedestein seem to be pretty good for some sizes at the moment, and they usually seem to have a hefty tread depth when they’re new.

Dear Tim,

My husband bought a new landrover defender 90 in the Spring of 2004. On 6th July 04 he took it to retailer to fix a leak on the driver's door side. They found the seal was damaged and replaced it. On 9th August '04 he took he back to have the same problem on the driver's side fixed because of a leak at the roof seam. There were a number of other problems with the driver's door such as rattling and window faults which had been looked at and repaired over the years. On 22nd March 07 they again looked at a water problem, with water gathering at the near side front footwell. The problem with leaking on the driver's side has persisted on and off and last year my husband asked them to look at a leak on the driver's side again. They were horrendously slow in getting back to him. They then said the car was out of warranty and as such they could not repair it free of charge. When my husband argued that this had been an ongoing problem, the chap in landrover insisted the leaks had been on the passenger side and not the driver's side. So much so that we began to doubt ourselves. My husband then asked for a run down of the servicing and repair history. When it failed to appear (after many months), he rang and asked them again. When the documentation arrived we found that the fault had indeed been on the driver's side. We are disappointed that we have been lied to and the matter has been protracted for the best part of a year. The driver's door still leaks, but if we want it fixed they say we have to pay for it.

Have we any redress?

Thanks and best wishes,

Patricia Robie, UK

Sounds like several separate problems. Is the latest leak the same as one or more of the earlier ones? If the dealer can identify the cause and it’s one of the things they were supposed to have fixed under warranty, you have a case for asking them to do it properly. A Land Rover is designed to be a rough, tough vehicle so it should be waterproof, but many dealers don’t really like this kind of work because it’s time consuming, fiddly and they get very little back in warranty payment. That’s not an excuse for them, just a fact of life. Remember it when you’re choosing your next car – when times are tough, businesses who give good service deserve to survive; those that were indifferent to us in the good times may find we’re indifferent to their problems now.

I bought my new car in May 2009 but it was manufactured in November 2007 can this still be "new" can I reject it.

James Gary, Great Yarmouth, UK

I’ll make my usual caveat that I’m not a lawyer so you may need proper advice, but generally speaking, age alone will not justify rejecting it - the car needs to have a serious problem. However, if the fact that it’s sat in a field for 18 months has led to significant deterioration, then demanding a genuinely new car would be justified. Have a very good look for any signs of leaks from any seals, including door seals etc. And check the specification to make sure it’s fully up to what’s listed for a May 2009 car. If all looks well, just enjoy it – you have the full warranty from the date of registration and there’s actually no evidence that a modern car suffers any damage or reduced life expectancy by sitting in a field for a year or so. With the current lapse in car sales, there will be quite a few cars of similar age being sold at the moment – if you discover that you are about to part with money for a car made in 2007, you could always try to negotiate a further reduction or a few extras thrown in, but don’t rely on it too much – lots of manufacturers are in the same boat and they’ve already cut their prices to the quick.

Hi Tim,

I am delighted with my LR3 (Land Rover ) but I am at my wits end to understand why it is so noisy on the road. I have been told, by a LR dealer, that it is caused by the tyres. It sounds just like the wheel bearings have worn but when I drive slowly the noise reduces significantly. The tyres are Good Year and they are not worn down to minimum levels yet. I have just over 41,000K on the Clock . I reckon the noise started at about 30,000K.

Can you advise please.

Aubrey Smith, Salt Spring Island, Vancouver

It could be the tyres. My tyre expert colleague tells me that Land Rover tyres develop “saw tooth” wear, which does sound like wheel bearing noise. This happens well before the tyre have worn down to replacement level. She suggests changing them round and see if the noise alters, but at 41,000 miles, surely it can’t be that long until they need changing anyway, so see if the noise goes then.