Hi all
can you help this relatively uninformed car buyer. I'm thinking of getting a new car, and would buy a diesel, but have been concerned by stories of common-rail diesels that, when they go wrong, go badly wrong.
Would an older diesel engine be a more reliable bet, esp. if with full service history? i'm thinking of something like the 2.0 dti engines that were in vectras about five years ago. i.e. the kind of engine that's still young at 100 000 miles.
cheers
slt
Edited by Pugugly on 15/09/2009 at 20:57
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I've been Ford common railing for the last 90-odd thousand miles and have had no problems.
On t'other hand, I'm certain there are people who've been landed with big bills.
On t'other, t'other hand, I don't think there is a common rail diesel with such a bad record you should avoid it at all costs.
I would say buy the car in the best condition your budget will allow and don't get too hung up on the type of engine.
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IMHO modern engines are much more reliable and effcient and quieter than old ones. I have had the new CDi style engines in a 57 Megan (1.9, 130bhp) and 06 Espace (2.2, 150bhp) covering 46 and 42k miles each with not a hint of a problem. Currently looking at replacing both with similar new ones if you were interested!
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I recommend doing some research on VAG 1.9 TDI PD units - generally regarded as about the best engineered modern diesel (post the PSA XUD range) provided you can find one that has properly serviced and run on the correct oil for its life. They're a tad expensive to tax and compared to common rail a bit lumpy or thrummy but on the move they're fine, built to last and the mpg you get will be close to official figures or better. There are a lot of related posts on this site over the years.
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If you are doing more than 15 miles per journey on avg. and those miles aren't town miles you should not run into abnormal problems.
However, if you are stuck in town, doing low miles, not letting the engine warm, the first thing you will suffer from is a sticky EGR valve. You may also have premature clutch / DMF wear. Excess soot build up from low temperatures in the exhaust from low / town mile-ing can also affect the injectors and fuel pump.
Each of these items can cost anywhere from £300 - £1,200 to fix, usually the latter.
Most modern common rail engines are very decent indeed. However, they are plagued with EU emissions regulations requiring significant nox gas and particulate filtering (rightly so). So instead of dumping a plume of black crud / soot out the back like old fords or VAG's used to do, they now have intelligent fuel maps and EGR valves/DPF's which job is to capture all this soot. If you don't do high enough miles or high enough speeds on a warm engine and if you don't maintain max cylinder pressure you will not generate enough heat to burn off this soot. You get rid of this soot by injecting fuel via a 5th injector to burn off this soot. But if you aren't maintaining enough heat (from say a longer journey) soot can build up and overwhelm the EGR/DPF causing it to stick and cause "limp home" mode. Also soot can build up on the injectors.
Edited by OldSkoOL on 16/09/2009 at 00:58
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This sums up why I don't like diesels, older ones are better as they are much simpler but I hate the sound, modern ones are just too risky out of warranty. Also petrol seems to be getting more and more reliable as diesels are getting more unreliable. A neighbour has a 406 HDI on an 03 reg and its been far more unreliable than both of me and my dads cars even though they are much older.
If I was skint and did 30k a year then an old XUD would really appeal to me, they are fantastic engines but for personaly given the milleage and sort of driving I do its pointless.
Edited by Rattle on 16/09/2009 at 01:18
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This sums up why I don't like diesels older ones are better as they are much simpler but I hate the sound .........
"hate the sound".....and this from someone who chooses to call himself "Rattle"!
(Only teasing! :-) )
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The PD engine is a great compromise. It has excellent performance and fuel economy, but without the expensive components (unit injectors and DMF aside) of a common rail unit. It is not a patch on a common rail for refinement though, with a very gruff, rumbly note and a few vibes, particularly at the top and bottom of the rev range. An excellent engine though. We have a mkIV Golf GT TDI 130 which goes like stink and returns 45-55 mpg depending on use. That's not driving for economy either - just driving the car normally.
I am a firm believer that common rail technology is inherently reliable. I personally know lots of people with common rail diesels, and not one of them has had a major fault with the fuel injection system. There are many elderly HDi Peugeots and Citroens, and TDCi Fords still driving around with starship mileages and performing well. We also had a dCi Renault which we took to 60,000 miles and the engine never gave a moment's trouble (the rest of the car started falling to bits, but that's not the engine's fault). It is true though that when a common rail system does go wrong, it can be absolutely wallet-battering, and easily write off an older car.
Common rails are also completely intolerant of misfuelling. Petrol in the high pressure pump will destroy it, and the resulting shrapnel will often take out the injectors too. That's a few grands worth just for the parts. A friend misfuelled his PD engined Skoda, drove it until it stopped, had the tank drained and refilled, and the engine fired up and ran. That was a year ago, and there have been no obvious ill effects.
What does seem to be a problem on all modern diesels is the Euro IV emissions gear. DPFs sap efficiency and clog up if the car does lots of short journeys, and the additive based system used by PSA can cost a fortune to maintain as the car ages.
The XUD turbo diesel was a fantastic engine in its day, but I drove one in a 306 D-Turbo recently and it reminded me how much diesels have moved on. Still a smooth engine (smoother than a PD), and remarkably zippy in a 306, but horribly laggy and unresponsive, and with a laughably narrow "powerband". Drops off boost (<2000 RPM) and won't even pull its own weight, but won't pull past 4k either. Tough and reliable though, with 250,000 miles widely accepted to be a minimum life for a well maintained unit.
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I think the biggest problem people are liable to run into with modern diesels is DPF issues if they rarely do longer journeys. The rest of the technology is *generally* reliable enough, but the good old DPF can be a nightmare if you don't do a minimum 40mph+ (constantly) for at least 15-20 minutes a week.
In certain areas (e.g. London, small off-shore islands) this can be near impossible. Best not to own such a car if that's the kind of place you do most of your driving. I've even seen VW adverts in magazines mentioning that DPF equipped diesels are not suitable for places like the channel isles with their low speed limits.
Conversely, with the PSA additive system, it may cost a fortune to top-up every 50k miles, but at least you don't get the DPF issues.
Funny how we have to be careful what kind of car we pick for where we drive these days, progress eh!
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