Diesel Reliability - Alby Back
Once again the subject of unreliable modern diesels has popped up on the forum. Also HJ alludes to it in his column this week. I switched to diesel 12 years ago and have covered almost 500k miles in various diesel powered cars since. With the notable exception of a Renault Espace they have all been faultless. The question I have for anyone who has access to the facts is this. What are the actual relative failure rates by brand /model on diesel versus petrol variants? It seems that we get a lot of vague tooth sucking and dire warnings but I have yet to see the actual numbers supporting this assertion. Not suggesting that there are not issues but my personal experience could not be more different. The cars I had prior to my diesels were all petrol and quite a few of them had mechanical failures. By comparison my diesel experience has been absolutely trouble free apart from that wretched Renault. The pay off is that in the roundest of terms I have saved circa £20K in fuel costs as a result.
The truth is out there but what is it?
Diesel Reliability - oilrag
Diesels have been fantastic at keeping us on the road without any engine related issues since 1991. Not even a `misfire` (remember that) or a failure to start first time, in 17 years.
Diesel Reliability - NARU
The point being made is that when a fault occurs, the newer common rail diesels can easily cost upwards of £1000 - partly because of component complexity [eg. dual mass flywheels], partly because there aren't yet the people to properly diagnose/repair.

I'm just starting on my third common rail diesel, and I did think twice before buying it.

My previous two (a BMW 330d and a Mondeo 130 TDCi) did good service but did hit engine reliability issues - the BMW was an EGR valve and an injector, the Mondeo an injector and the turbo. Prior to these I had petrol cars with no problems at all.

My overall feelings are that diesels are still reliable, but if/when a breakdown occurs you can be talking serious money. in some cases enough to scrap a 6-8 year old car!
Diesel Reliability - Alby Back
I do acknowledge the cost of repair argument but what I would like to know is what is the relative risk. Are we talking about 50% of diesels failing or 5% or 1% or what? And how does this compare with the equivalent petrol models?
Diesel Reliability - isisalar
The amount of common rail and particulate filter problems /expense posted on here were certainly enough to put me off buying a CR,much as I would have liked one.It would be interesting to see the statistics though.
Diesel Reliability - Falkirk Bairn
Saving £5-£10 / week burning diesel appeals - however if there is a bill of £1000+ for injectors, turbos and DMF then I think a economical petrol has merits.

I have a diesel and get about 40mpg on a decent run, my DiL has a new Honda Civic - average over 40 and can get 45-47 on a long run - it is 2 years old and has been consistent in the mpg..
Diesel Reliability - kingslea
There is no commercial gain in releasing car reliability stats, least of all from car makers. Extended warranty companies only seem to give relative repair costs on older vehicles. We will never see accurate breakdown figure from the recovery people either, they have too much to lose with their commercial links to car manufacturers.
Diesel Reliability - Falkirk Bairn
. Extended warranty companies only seem to give relative repair costs on older vehicles. We
will never see accurate breakdown figure from the recovery people either.

I had a friend with a Mondeo - a few months out of warranty buty with a extended warranty through insurance - they did not cover injectors - BIG DOSE of REDEX put the lights out and he traded it in!
Diesel Reliability - Avant
Yes, and the stats can't take account of how a car is driven: even a full service hostory only tells half the tale. Look at the current Volvo S60 thread, where DP's has clearly been looked after by its previous owner, and PE's hasn't.

The only constant is the one mentioned by Marlot - when a diesel does go wrong it'll probably be more expensive to repair. It also seems that modern diesels are more complex than older ones: the ancient Perkins Prima would rattle on for years and take all manner of abuse, while the Maestro or Montego crumbled visibly around it.

I don't hang about, but try to drive with reasonable 'car sympathy' and (touching wood) I've had 40 years of reliable cars, including seven Renaults in a row. OK, I've been lucky, and there are plenty of good drivers who have been less fortunate, but I think it makes a difference.
Diesel Reliability - DP
I've driven probably 250,000 miles in various diesels, the vast majority of which being the older non common rail type, and never had an engine related problem with any of them, if you exclude failed glow plugs. The cars include a VW Golf mk2 1.6D, Peugeot 306 D-Turbo (XUD), a Polo 1.9D CL, two Focus TDDi's, a Megane 1.5 dCi 106, a mk2 Mondeo 1.8TD and our current family chariot, a 2004 Grand Scenic 1.9dCi, currently on 52k and still punchy, smooth and with near zero oil consumption.

Admittedly, the mileage on the common rails has only been about 30k of the total covered, but the only trouble has been glowplug failures. The Fords stand out as being the most impressive having literally been completely troublefree in the engine department in over 150,000 miles covered between them.

I agree with Avant, a lot hinges on maintenance and driving style. I've always made a point on the turbo engines of driving sympathetically until warmed up, and allowing a minute or two of gentle running or idling before switching off, for example. Regular level checks, servicing religiously to schedule (or sooner), and with particular attention to fuel system maintenance such as frequent filter draining and replacement.

That said, I am aware that one fault on the Scenic could cost more than the maintenance bills on the rest put together, but I'm a natural optimist ;-)


Diesel Reliability - Westpig
it would seem to me that cars in the past 10 years have become considerably more reliable than they were of old (petrol and diesel)...and...for daily running costs reasons many people have swapped from petrol to diesel more recently

however, you can't really equate the reliability of diesels versus your past petrol car reliability, if my above assertion is correct....because they've all become more reliable, so if you'd stayed with petrol they'd have been more reliable as well

I can't answer the poster, but a good friend has just had an £800 diesel fuel pump bill on his 5 yr old Transit which was an eye waterer...and makes me think a bit with our long distance car being a 2.0 turbo diesel that is just out of warranty

Diesel Reliability - Pugugly
Three words spring to mind, party, warranty and third.

Edited by Pugugly on 26/04/2008 at 23:07

Diesel Reliability - mattbod
Been running a Skoda Fabia VRS for three years and that has been very reliable. The umoe Duse engine is still available in VAG cars and although a noisy engine is reliable from what I have heard except for DPFs on the top 170 BHP cars. It is the complexity of high pressure injection systems, sophisticalted variable vane turbos, dual mass flywheels and exhaust gas recirculation that means costs can be prohibiive when htings go belly up. I am afraid the old "there's less to go wrong dos not stand up any more".

You still ave oney on Diesels everyday though becasue the price differential is only between 95 Ron and Derv. Most modern petrols run much better on 97 Super Octane and so you are paying the same anyway. Go for a japanese or German Diesel and you should be o.k. My brother in Law works for a Ford dealer. I was going to consider an Focus 2.0 TDCI. A great car but he stated that the engines are prone to problems and cost the earth to fix! Alternatvely if you are not in a hurry seek out a late 80's Mercedes 300D. Indirect Inline injection pump, simple ohc design and beautifully smooth. That at and the 190D 2.5 put and modern Diesel to shame for refinement. Oh I know a bloke who has one wih over 500,000 miles on the clock! (190D 2.5)
Diesel Reliability - Screwloose
Go for a Japanese or German diesel and
you should be O.K.

What; like a Mazda 6 - or a Merc CDi - or a VAG V6 TDi - or a BMW?

You nailed it in the first paragraph; diesels can be [and were] simple and reliable - they just can't be clean too.
Diesel Reliability - mattbod
Absolutely right although mazda normally get things pretty much bang on with reliabiliy so I am surpirised if their Diesel is dodgy. After all they made the Rotary reliable! I know a guy who has an A4 2.5 TDI which ran fine until the dealer overtightened the cambelt tensioner at a service and wrecked the engine when the belt snapped! Luckily they forked out. Woudn't touch a Merc CDI as it costs about £600 to change the glowplugs!

P.S sorry for earlier typos I meant of course PUMP DUSE. Must learn to type!
Diesel Reliability - Screwloose
The Mazda 6 diesel does have just a few niggles..... Prepare to be surprised....

Volume 1


Volume 2


don#t know what happened there, Screwlose, but I've fixed it

Edited by Pugugly on 26/04/2008 at 23:50

Diesel Reliability - Alby Back
Thanks for all the replies so far. As usual there are some very interesting personal views being expressed but also as usual, with all due respect, no hard facts have been presented which quantify this assertion that modern diesels are inherently unreliable. In the current absence of any numbers to analyse, here are some trivial ones to be going on with.

As I previously stated further back up the thread. I guesstimate that the effect on my fuel costs over my past 12 years of dieselism is a gain of £20k. Apart from the accursed Renault all my cars have been ultra reliable. As it happens the Espace was leased and therefore under warranty so it didn't cost me anything but my patience.

Leaving my gallic encounter one one side, just suppose for a moment we look at a scenario where over a similar 12 year / 500k miles period that I have 6 more diesel cars. Let's imagine that every other one suffers a catastrophic DMF failure or some such. Let's allow, say, £2000 of extraordinary cost in each instance. Even if fuel were to remain at today's bargain prices I would still be something like £14k in pocket at the end of the 12 years by sticking with diesel and assuming no problems at all with the petrol alternatives. So in other words even if 50% of diesel engined cars suffer a failure of this magnitude during their "lifetime", for a high mileage driver it is still measurably and appreciably cheaper to run a diesel with or without a warranty.

OK so I'm posting drivel to make a point. I don't believe for one moment that the chances of major failure are anything like 50%. Based on my own experience they are in fact, minimal. I accept the fact that it may happen one day but I might also have a substantial win on the lottery. Not for one moment do I deny that some cars have had problems and when they do they are expensive to fix but at the risk of being repetitive, let's see the numbers please.

Without the evidence to the contrary you could be drawn to the conclusion that this is yet another example of the British propensity to love wallowing in and spreading bad news when in fact the reality is something quite different.

Diesel Reliability - Screwloose

As already said; nobody's going to reveal the true facts. [Look at the Mazda and Ford dealers' attitudes of blank denial.]

My own guess is, over a 3 yr period, that 5-10% of CR diesels will suffer a serious fault [over £1000] and far less than 1% of petrols.

However; given the appalling consumption figures of the latest diesels and the cost of maintaining their power-sapping emissions gear; the price differential of the fuel; the extra capital cost and the increased maintenance costs - petrol is now cheaper overall.

I'll stick with my [old-tech] diesels though - I just like 'em.
Diesel Reliability - mattbod
Think the general consensus here is that you should be o.k but there is awful lot MORE to go wrong and it is a lot more sophisticated stuff and hence costly should you be unlucky If you are lucky fine and touch wood I, like you have been but Screwloose above makes a valid point. If you want statistics write to the AA or RAC if you are a member or, best of all when you take your car in and if your mechanics have brain, ask their advice.

You pay your money and you take choice.
Diesel Reliability - gordonbennet
Speaking personally, and i've run diesels since about '83 or so, can't exactly remember.

I never had a problem with diesels i've bought, including the couple i've bought with engine problems cheaply which were simplish to repair/overhaul, but as already said these were very old school diesels and as such were built for reliability and fuel consumption not performance. (Granada 2.5 peugeot lump completely worn out at 80k through non servicing, mk1 golf holed piston, both easy repairs and years of service after)

Couple of observations though.
The best diesels i've owned have all been well serviced throughout their lives, none of this 20 thou miles rubbish.
Whilst in my care the cars have been driven hard, only way to make the old type go, but always allowed to warm up before thrashing and allowed to cool if turbo'd.
Whether my own experience is common i know not.

The stories we hear of failures with the common rail motors has put me off buying used cr diesels as i don't want someone else's neglected or misfuelled or generally abused rubbish.

In fact almost every engine failure i've known about has been with owners i know do not service their vehicles adequately or treat them with care, someone in my own family bless em comes under this banner and always has fuel system problems on their diesels, and can't see the connection.

I'm not terribly convinced by all this hype about how fantastic modern oils are compared to twenty years ago, similar to hearing a politician speak, the makers tend to tell you what you want to hear. I wonder for example if there's any relation to the apparent short life of x trail turbo's and some starship mileage oil change intervals.
I've always been under the impression that oil has to work very hard in a diesel.

All my own observations, and i wonder if someone who looks after their vehicles would be able to run supposedly troublesome cars for years with no probs whatsoever.

You seem to have had good fortune with your diesels Shoespy, i'd hazard a guess you have treated those vehicles well though.

Diesel Reliability - Alby Back
You may be right GB. I do try to drive with an amount of mechanical empathy without sparing the horses. Like you I don't ask too much of the engine until it is up to temperature. Personal rule is no more than 3000 rpm until up to temp, and I always allow it a minute or so to "warm down" before switching off. My cars also always get serviced on time as per manufacturers schedule albeit by a local garage. I am also careful never to dump or slip the clutch and use first only to get the wheels turning and save the harder acceleration for second upwards. Maybe it helps.
Diesel Reliability - oilrag
Agree with everything in your above post GB
Diesel Reliability - b308
Interestingly enough petrols are starting to get more complacted as well - probably the most complicated engine on the market at the moment is not a diesel, but a petrol - the VW 1.4 TSi with turbo and supercharger....
Diesel Reliability - Galad
>Look at the Mazda and Ford dealers' attitudes of blank denial>

Is it any wonder considering the lucrative warranty work they can coin in to make up for the narrow margins on new car sales?
Diesel Reliability - madf
We have had this debate before.
It's all about Delphi systems which are marginal.

Guess who uses Delphi?

Diesel Reliability - Number_Cruncher
>>the lucrative warranty work they can coin in

Not really.

Warranty work is not lucrative for dealers. First, the hourly rate that the manufacturer pays the dealer for warranty work is nowhere near the hourly rate paid by customers. Second, each warranty job is followed up by a more torough evaluation and coding work by the dealer to enable them to make the claim - this can take some time to find and enter the correct codes. Third, there's a reasonable risk that the warranty work will be rejected, either the whole job, or a proportion of it during a warranty audit, which manufacturers like to spring onto dealers.

In short, dealers are much happier doing servicing work for cash paying customers.

Diesel Reliability - Number_Cruncher
>>none of this 20 thou miles rubbish

If this really were true, then engines would be failing with great regularity. The technical side of this forum would be full of people asking about re-bores, crank grinds and new pistons. This isn't the case, therefore, the 20,000 mile oil changes are appropriate for most vehicles where this is specified.

I would not be surprised to find that most cars reach the scrapyard without their engines having ever been opened up for anything other than routine servicing.

Diesel Reliability - Alby Back

I would not be surprised to find that most cars reach the scrapyard without their
engines having ever been opened up for anything other than routine servicing.

Nail squarely on the head of my point NC.

Maybe the statistics I am asking for are not yet in the public domain but if this is the case, I call upon anyone who knows how to ferret them out to please do so.

So far, all we hear is the automotive equivalent of " I, and someone I once heard of, bought a bad apple from that supermarket."............ "Therefore, if you buy apples from them, they are more than likely to be bad." Sounds like a bit of an over reaction when you put it like that doesn't it?

Perhaps I should ask the Mods to change the thread title to " Diesel reliability - the facts" if it's not too late?
Diesel Reliability - smokescreen
I honestly think the only way this will be settled is if there's a website dedicating to taking records of problems people have had with their cars, and have some simple way to verify the matter. Get other car forums to make the site a sticky and encourage those who are involved to fill in a quick 5 minute form on the matter.

Whilst there are people in the industry who clearly have solid experience in the industry, a bigger sample would really help show who's particularly weak and who's particularly reliable, and may even encourage manufacturers to somehow improve on these matters?
Diesel Reliability - b308
To be fair to the manufacturers they have improved reliabilty beyond all recognition, as anyone who has owned/driven a 60s or 70s car will tell you... even more impressive as cars have got so much more complcated than they were with all the add-ons such as ABS, airbags, engine management, etc, not to mention all the "luxury" electrical items.
Diesel Reliability - Number_Cruncher
I think that although there are many factors which skew the type of people who will post on a site like this, the posts in technical do give us a snapshot of what sorts of faults are prevalent - in other words, this site itself is a potential source of the data you seek.

In a purely unscientific way, the feeling I get, based upon the numbers of posts in technical is that CR diesel failure are about as common as catastrophic engine failure itself, but, dual mass flywheel failure in particular is becoming rather more common.

Engine failures are so rare these days. In the late eighties, i the Vauxhall garage where I worked, top end overhauls, valve stem seals, camshafts, fitting GMX engines were all reasonably common tasks. Now, according to my ex-colleague who works there still, these jobs are rare and unusual, and so take much longer to do, because even the dealership mechanics do not have the level of familiarity required to turn the jobs round quickly.

Diesel Reliability - A11DNL
I wonder if HJ has any record of the fuels used by the "problem" diesels he reports? Or thoughts about the reliability implications of veggie diesel in CR engines?

(I now run my MINI D exclusively on BP Ultimate because it is quieter and more responsive that way, and the few pence more per litre doesn't bother me when I never get LESS than 50 mpg.)
Diesel Reliability - oilrag
It seems to me that the `best indicators` are going to be provided by independent Mechanics/Techs such as Screwloose, who have an overarching overview and yet no main dealer/Manufacturer agenda that could impede honesty.


Edited by oilrag on 27/04/2008 at 12:12

Diesel Reliability - qxman {p}
I know that in the Motoring Which yearly report, when they used to use the 'star rating' for 'faults', 'niggles', 'breakdowns' the diesel versions of popular cars nearly always scored less well than the petrol versions.
I have never seen any hard statistics, but then I supposed manufacturers prefer to keep ALL such data confidential!
I have only anecdotal information - I work with a number of people of commute in diesel cars and they nearly all seem to have had either fuel system or DMF-related problems. IIRC the only guy who hasn't drives a Passat, which seems to be a good one. I don't recall anyone talking about major problems with petrol engines. I think most small-time independents can fix a petrol problem easily and fairly cheaply, whereas with a diesel it seems that even small defects cost big money to fix and there is a dearth of repairers with the right kit and skill set.
Diesel Reliability - GroovyMucker
... in the Motoring Which yearly report when they used to use the 'star rating' for 'faults' 'niggles' 'breakdowns' the diesel versions of popular cars nearly always scored less well than the petrol versions. ...

Although that could have been - at least partly - because diesel drivers drive higher mileages, so more opportunity for things to go wrong.
Diesel Reliability - gordonbennet
Point taken NC, but doesn't oil do other things other than protect bores from wear, especially diesels where the fuel itself is a fine lubricant for bores etc.

I'm thinking more of the extremely small bore oilways involved especially with turbo's, of which there are a number of regular failures reported, also hear periodically of timing chain guides and other such parts wearing out with catastrophic failures.

I'd be surprised if anyone making enquiries on our technical forum about overhauling their worn out engines would be leaving their oil changes to these astronomical mileages. I'd be more inclined to think that people who do the bare minimum to their vehicles come into to the use and dispose category, and i can't see them dismantling an engine and getting rebores etc if they can't be bothered to change the relatively cheap oil. They've probably disposed of the vehicle long before that, after the second or third turbo failure or the original cambelt snapping long before serious engine wear could result.

Vast majority of new vehicle private buyers are going to replace within 100k anyway, hence the often heard suggestion on this forum, its not worth looking after/rustproofing/servicing etc as i'm going to sell it soon anyway, i'm not criticising that viewpoint, but there are some of us that prefer to look after our things better than that.

By the way, you come from old haulage background, at work when i'm loading alongside several other transporters all at approx 800rpm with the pto's running, you wouldn't believe the stink of burning oil that some of these very modern trucks make, and i believe most of this premature wear is down to ridiculously high service intervals, not that it matters of course because most of them will be at the docks by 5 years old being exported to another thirld world country, damage already done.

Disposable world, not for me.

Diesel Reliability - mattbod
I asked my brother in law about the ratio of cars that come into his garage with major engine problems and failure and he said that almost all of them, say 98% are Diesels. According to him the Petrols are far more reliable. I wanted a Focus 2.0 TDCI as previously mentioned,he said avoid like the plague. My sister traded up her mark1 Focus and tried a 1.6 TDCI and loved it but he partner refused to let her have the Diesel "I've got to work on the thing when it goes bang" so she got a 1.8 petrol: far simpler no turbo, no high pressure pump, no fuel rail.

No one can provide statistics that I am aware of but if you want the lowdown on engine reliability and comparisons talk to a technician. They are the best source of information. I bought my car with the TDI 130 Pump Duse engine in it and it has been fine. i bought that on he back of a recommedation from by brother in law who said the best Diesel Ford fitted was this motor in the Galaxy as i dn't want a people carrier bought the Skoda. Yes it's complicated as the injectors are run off individual plunge pumps for each cylinder and strain can high. You have to use a special oil but I know these engines can do mega miles if looked after. Another good source of advice as to modern Diesels is to go and have a word with the guys at your local TAXI RANK: they have seen it all.

Edited by Mattbod on 27/04/2008 at 14:14

Diesel Reliability - b308
If things were as bad as you indicate, Matt, it would be all over the Press, as its isn't I'll take these rumours of mega problems with diesels for exactly what they are, rumours....
Diesel Reliability - Pendlebury
I bet HJ wishes people would stop sending him e-mails of the rumoured problems they have with their diesels - especially as they are only rumours.

Also I wonder if the jazz would continually be the most reliable car in the UK if it had a diesel engine - just a thought !

Edited by Pendlebury on 27/04/2008 at 20:40

Diesel Reliability - Alby Back
I don't think anyone is denying the reality of there being issues. All I am trying to get at with this thread is to gain some understanding of the size of the problem.

I only stumbled upon this website about a year ago and if anyone had previously tried to convince me, for example, that Ford diesels had reliability issues I would frankly have laughed in their face. My views prior to reading some of the tales of woe on here were entirely subjective and based upon my own experience or that of people I happen to know. On that basis I was simply not aware of the existence of DMFs for example, never mind their vagaries. My experience, it would now seem, is one of astonishingly charmed luck if the collective view of some forum members is to be taken as fact.

I was simply wondering if anyone could quantify any of this. It would seem not, but thanks to all respondents anyway.
Diesel Reliability - PhilW
"Another good source of advice as to modern Diesels is to go and have a word with the guys at your local TAXI RANK: they have seen it all. "

Exactly - so why are the vast majority (?) running diesels if they are so unreliable?
Where are all the questions on the Technical part of this site about "unreliable diesels"?
Diesel Reliability - carl_a
>>The pay off is that in the roundest of terms I have saved circa £20K in fuel costs as a result.

How have you worked his one out shoespy, I think even at 500k you are overestimating the savings.
Diesel Reliability - mattbod
Just to answer b308, not saying things are bad in general but certainly from my brother in law's view of things,he sees a lot of problems with Ford Diesels, maybe that is just his garage. Screwlooses' links on the Mazda Diesel shocked me so there is obviously big problems there given the number of replies. However my car has VW's unit injector (PD) 130 engine. It is not a Common Rail and has been very reliable indeed

Diesel Reliability - b308
But what %ge are we talking? - diesel is now nearly outselling petrol but there are no scare stories of the sort that make progs such as Watchdog - I agree it would be nice to have the stats, but as others have said the problem with forums is that they skew the picture as many people will only go on them and moan if they have a problem, and even then we don't know if the problem is genuine or "owner induced".

And then there are those around who hate diesel and will post at any opportunity to make things look worse than they are...

All I can say is that after 15+ years of diesel ownership I've only ever had one problem (with an early Vectra), and many of my friends have diesels and also no problems... which seems to buck the scare stories....
Diesel Reliability - curious
The very fact that examples of a much maligned car such as a diesel Mondeo exist with huge mileages on them having never had any major work done to them suggests that these cars can and do provide trouble free ownership for some people.

With the latest methods of car production, you would have to say that any two new cars off a production line will be exactly the same. So why will one reach 300k miles and the other need to be scrapped before a third of that? I cannot accept that driving behaviour does not play a huge part in many of these issues.

I think you have to break down the variables.

Driver Style

I think people need to think of cars as a machine. The biggest single variable affecting the longevity of any machine is its operator. Clearly CR diesels are hugely complex and are utterly unforgiving of poor driving habits and poor fuel. The cost of repairing faults on these things is huge. Petrol engines are far simpler affairs and are more forgiving of poor operators.

I'd imagine that anybody who has had diesels for donkey's years without complaint will continue to have none from these engines. If you're the sort of driver who is constantly having to have things repaired on your car, steer very clear of them.
Diesel Reliability - MikeTorque
Some cars that come off a production line are lemons, in other words they have more than their share of defective components. My wifes last Citreon Xsara was one such lemon, no wonder it was cheap when she purchased it (before I met her), she px it with several known faults and the dealer didn't bother at all as the car was A1 condition from the outside. Her previous Citreon ZX diesel was trouble free until is reached 90k then it started to fall apart so she sold it. Her Focus diesel is trouble free.

I agree that a driver with mechanical sympathy greatly helps the reliability of any engine petrol or diesel.

Diesel Reliability - qxman {p}
I can imagine that driver behaviour might impact on the lifespan of a DMF or even possibly a turbo. But most of the CR-related problems on here have been with the fuel system, and I can't see how it would 'know' whether the car is being driven hard or not. Presumably the pump just whirrs away, the ECU gets its signals from sensors and the injectors get switched on and off.
Servicing would related mainly to oil and filter etc and you don't really hear of ANY car having problems with major engine block wear these days, even turbos seem reliable.

One of the common problems I've noticed is that Fords 'lose their injector coding' and have to be recoded. I'm not exactly sure how this would happen, but I can't see that the owner could possibly be responsible, it sounds more like a problem in the design of the ECU for this to happen.
Diesel Reliability - mattbod
I agree but some sympathetic stick is useful too. Many engines suffer from never loosening up because they are driven with kid gloves. HJ recommends hitting 4500 rpm a couple of times a week through the gears to blow out all the muck and soot. Diesels take time to warm up though as thermo dynamically efficient so I never use more than 2500 until my car reaches 90 C. Plus two minutes idle after a hard run.
Diesel Reliability - Chrome
"Some cars that come off a production line are lemons, in other words they have more than their share of defective components. My wifes last Citreon Xsara was one such lemon, no wonder it was cheap when she purchased it"

Crikey - sorry bit off the topic but Mike Torque - I also had a ZX & then a Xsara! I agree - my Xsara Mk2 (from my mum who had owned from new) creaked badly , had trim that fell of, rear seats that rattled in the 'up' position, front seats that made my back ache, brakes with no feel, a self-destruct oil dipstick & air con that usually didn't. My Kia Rio diesel really was an upgrade from this awful car!

Diesel Reliability - britinbrussels
Can it be concluded that the TDI PD engines suffer less problems than CRs? Do TDIs have dual mass flywheels - I understood some of the higher power ones do? I'm interested as I'm considering buying a VAG car (Ibiza or Polo) with a 1.4 TDI PD 80hp. Any thoughts on this? As some background, I have some other reasons for this choice, here in Belgium you get 15% off the new price of sub-105g/km cars - that leaves a choice of a Prius, Polo Bluemotion, Ibiza Ecomotive (waiting for the new one) - and probably the new Fiesta Econetic in a few months...
Diesel Reliability - prm72
I have been reading this thread with great interest, re: scaremongering, a few years ago i bought a vectra b 1.8 petrol, with 24k miles on it and then read on various sites including this one that they were rubbish and to steer well clear, i sold it after 3 years with 120k on it and the only thing that ever went wrong with it was an idle control valve, it was a great car so i bought a vectra c 2.0 dti, and all i ever read about these was that the vp44 pump was carp and cost 2k to replace, fuel return pipes and injector seals need renewing on a regular basis, bottom pulleys break up and fly off, well i ran that from 34k to 128k over 3 years, and nothing ever went wrong with the car, it had been fantastic. I was going to replace it with a petrol because of all the scary stories about common rail, but i do love my diesels and after driving an S60 D5 auto i couldn't resist, i have checked up on this particular engine and it seems to be quite reliable for a CR lump, at the moment i'm enjoying it, and i'm not going to worry what might happen anymore.
Diesel Reliability - nick74
my Xsara Mk2 (from my mum who
had owned from new) creaked badly had trim that fell of rear seats that rattled
in the 'up' position front seats that made my back ache brakes with no feel
a self-destruct oil dipstick & air con that usually didn't.

Xsaras come in for a lot of stick, but I've had a Xsara HDi for the past 2 years, bought very cheaply off ebay. I cover about 20-25k a year in it and its been fine. Only problem its had was the COMM 2000 unit in the steering column - about £165 to replace.
Diesel Reliability - mattbod
Britinbrussels I have driven the 1.4 TDI PD in both Fabia and Roomster and think it is a great engine. It's a three cylinder and has a nice growl under acceleration and can return late 50's mpg all day. In regards to PD, I have no statistics but all those mini cab Passats with hundereds of thousands of miles can't be wrong. Iis a well proven engine hving been around for at least 8 years starting of in the Audi A2. I have the 4 cylinder version and it has given me no trouble.

PD is unit injector technology which means that a low pressure pump caries fuel to (three in this case) individual plunge pump injectcors per cylinder driven from the camshaft. Only caveat is that these engines have and I mean HAVE to be run on special oil. It is a system commonly used on trucks: great for power, torque and economy but not so good on noise and emissions hence VW ditching it for CR. Try the SEAT and see.
Diesel Reliability - DP
>>Xsaras come in for a lot of stick

Ditto the Renault 1.9dCi engine which was widely regarded as a dog in its early incarnations, due to a spate of EGR/turbo failures. This was fixed with a redesign after a couple of years, and I have never read of anything other than isolated problems with its Bosch common rail fuel system. My research hasn't thrown up any inherent faults with these later engines, but the stigma has stuck, meaning they're very attractive on the used market.

We bought a fully loaded Grand Scenic with every single optional extra apart from climate control and leather. 36k, FRSH, 2.5 yrs old, for 40% of its new retail price. Now on 52k, it's still lively, responsive, refined, frugal and, touching a big piece of wood, hasn't skipped a beat mechanically so far. It will do 9-10k (the longest I've let it go between changes) without the oil needing to be topped up, and I've changed two glowplugs. That has been it. Was following SWMBO in it last weekend while she was giving it some beans, and not a puff of smoke out the back, even with foot to boards up a long hill when 5-up.

I ignore Renault's 18k intervals, and give it a midpoint change with a good fully synthetic 5W/40 oil and a new filter. Other than that, it gets no special treatment, and is generally driven pretty hard.

Diesel Reliability - Ravenger
Only problem its had was the COMM 2000 unit
in the steering column - about £165 to replace.

Funnily enough the exact same unit had failed in the Xsara I bought from auction a few years ago. It had 100,000 on the clock, and turned into a money sink, as one thing failed after another. I had it a year, and couldn't wait to get rid of it. Funnily enough virtually the only thing that didn't cause any trouble was the 2.0 HDi engine. It sounded like a tractor, but gave pretty good performance and economy.
Diesel Reliability - qxman {p}
I stumbled across as interesting site for anyone thinking of buying a diesel:


The 'Good Diesel /Bad Diesel' page is worth reading.

Of the Ford/Jaguar TDCI he states:


Delphi strike again and win the wooden spoon for badly designed injection system. Despite the cars themselves being good a truly awful fuel system lets things down in a big way. Having to 'code' injectors into the ECU with the intention of creating more money for the dealerships is about as underhand as it gets Is this the future??? '

There is also some explanation of how the various different systems work. Well worth reading before you buy ;-)
Diesel Reliability - Screwloose

Having seen some of "Diesel Bob's" other pronouncements, I'd take his comments on the TDCi with a large pinch of salt.

The necessity for the injectors' software correction factors had nothing whatsoever to do with dealer workshop profit margins.
Diesel Reliability - qxman {p}
Having seen some of "Diesel Bob's" other pronouncements I'd take his comments on the TDCi
with a large pinch of salt.

He appears to run a successful business fixing diesels. I assume he knows a bit about the subject.
The necessity for the injectors' software correction factors had nothing whatsoever to do with dealer
workshop profit margins.

I think I understand the reason for correction factors. However it does seem to be the case that an awful lot of queries in the 'Technical' forum are related to TDCI injector 'recoding'. I don't see this for the other brands out there. Presumably there is something wrong somewhere, even if extra workshop profit is not behind the problem?
Diesel Reliability - Screwloose

There is indeed something very wrong for the TDCi to need individually tailored software correction for it's injectors. Other users of those same Delphi injectors don't have that need. Odd that.....

Diesel Reliability - akr
An observation.
My 93 TiD 150 (2005) is on a 2 year 18000 mile (whichever comes first) service schedule. The wife's 93 convertible (same engine on a 2007) is now back to a 1 year 18000 mile (whichever comes first) service schedule.
Since we're talking long term reliabilty I just wonder if there's any significance in that. I've always thought 2 years is a long time between services which is why I drop the oil every 9000. I wonder if Saab have decided likewise about the 2 year intervals.
Have Vauxhall done the same with their cars that use this engine?
Diesel Reliability - nick74
>> Only problem its had was the COMM 2000 unit
>> in the steering column - about £165 to replace.
Funnily enough the exact same unit had failed in the Xsara I bought from auction
a few years ago.

Yes it seems a common problem on most multiplexed PSA cars of around that age. The COMM 2000 on mine was date stamped about 3 months after the car was registered, so I assume it had already had one replaced before.
Guess who the COMM 2000 units are made by?
Diesel Reliability - curious
What is the verdict on a HDI 407? They seem to be relatively cheap and don't figure on the technical pages too much. Are they a money pit or a good car with relatively poor badge?