Modern diesel reliablity

[mat205125]

HellDiver said:

mat205125 said:

Not a single person has managed to report an independent, unbiased, statistical analysis of the probability of failure of parts of, or entire, modern diesel and petrol engines.

I suggest you go and look at any Astra or Vectra forum and check out the thousands of threads about failed inlet manifolds on the Z19DTH engine.

Or go to any Ford forum and check out the injector failures on the 2.2TDCI.

How about Merc ceasing production of their latest CDI engine for months upon months due to injector faults?

There are plenty of modern diesels with faults that regularly occur no matter if they're serviced or not.

Not doubting anything you've stated, however those kinds of reports of failures do not paint the entire picture in an unbiased manner, nor form the basis for an accurate approximation of the entire population of that engine in the field - People don't start a thread titled "I have driven my Z19DTH enginned Vectra all month, and nothing has broken!".

Rover K-Series always blow head gaskets.
E36 M3's Vanos will always fail.
996 Porsches will always suffer RMS failure.

Whilst I'll accept that there is no smoke without fire, the internet is awash with reports of direct and indirect reports of problems of this kind that may be massively overstated when viewed as a failure ratio of the entire population of the engine type.

[Thudd]

STdriveRS forum makes interesting reading.
Eg: This thread where they all list their fault

[Futuramic]

havoc said:

flakeypaul said:

Can you please now tell me that Renaults don't break, ever. Especially the diesels

A modern CR TDi is a fair bit more complex than an n/a petrol, and the components are under more pressure and more stress. So I'd be very surprised if they last as long, or are as reliable. Finally, direct injection has been seen on the VAG FSi engines to coke-up the inlet tract and the back of valves a lot quicker. I'd expect the same in a diesel.

But the comment above about maintenance is also very important - and as someone said on a different thread, a lot of people now treat cars like white goods.

Personally I wouldn't get a modern TDi unless:-
- I did very big mileage; and
- I got a decent a/market warranty to cover the big stuff
...but they're still the best answer for 20k+ mileages.

I definitely would not expect the inlet tract and valves to coke up on a direct injection diesel as they only thing passing through them is air. The exhaust will, granted, but not the intake.

[flakeypaul]

I'd be really interested to see somewhere where absolutely everyone posts their diesel experiences, not just the ones that break. I suspect they would look a lot less unreliable then (nobody goes online to say how great their car is, they just moan when it needs attention).

Let's hope I don't become one of them!

[HellDiver]

Futuramic said:

I definitely would not expect the inlet tract and valves to coke up on a direct injection diesel as they only thing passing through them is air. The exhaust will, granted, but not the intake.

I suggest you do some research in to how EGR works.

Exhaust gases are introduced back in to the inlet tract, most often just after the intercooler.

- inlet side of an EGR on a 2.2CTDI Civic

- a VW inlet manifold.

Edited by HellDiver on Tuesday 1st June 10:59

[TheCarpetCleaner]

mat205125 said:

HellDiver said:

mat205125 said:

Not a single person has managed to report an independent, unbiased, statistical analysis of the probability of failure of parts of, or entire, modern diesel and petrol engines.

I suggest you go and look at any Astra or Vectra forum and check out the thousands of threads about failed inlet manifolds on the Z19DTH engine.

Or go to any Ford forum and check out the injector failures on the 2.2TDCI.

How about Merc ceasing production of their latest CDI engine for months upon months due to injector faults?

There are plenty of modern diesels with faults that regularly occur no matter if they're serviced or not.

Not doubting anything you've stated, however those kinds of reports of failures do not paint the entire picture in an unbiased manner, nor form the basis for an accurate approximation of the entire population of that engine in the field - People don't start a thread titled "I have driven my Z19DTH enginned Vectra all month, and nothing has broken!".

Rover K-Series always blow head gaskets.
E36 M3's Vanos will always fail.
996 Porsches will always suffer RMS failure.

Whilst I'll accept that there is no smoke without fire, the internet is awash with reports of direct and indirect reports of problems of this kind that may be massively overstated when viewed as a failure ratio of the entire population of the engine type.

In fairness, the rover was a particularly bad example to highlight the unbiased point.

Over the years, I have owned 2 rovers, and I have had friends who have had cars with K series engines, some kit cars, a lot of normal cars and a lot of classic rovers. Also people I work with with newer rovers, including my current next door neighbor.

I do not know a SINGLE one who has not had a head gasket failure throughout them owning the car. Not one. Probably talking about 50 or 60 different types of rovers with different types of driver.

Even my grandmothers Rover 45, starting to drink water. 04 plate with 32,000 miles on it.

Rover = guaranteed HGF.

[havoc]

HellDiver said:

Futuramic said:

I definitely would not expect the inlet tract and valves to coke up on a direct injection diesel as they only thing passing through them is air. The exhaust will, granted, but not the intake.

I suggest you do some research in to how EGR works.

Exhaust gases are introduced back in to the inlet tract, most often just after the intercooler.

- inlet side of an EGR on a 2.2CTDI Civic

- a VW inlet manifold.

Cheers HD - saved me finding similar stuff.

DI, on ANY engine, means the inlet valves don't get 'washed' by the fuel and as a result DO coke up. (EGR is frankly a f'n awful idea (except for emissions ) - forcing the engine to eat it's own st, in a sense!)

As a pertinent aside - does anyone know if such coking would be covered under even a manufacturers warranty, let alone an after-market one???

[thinfourth2]

From what i can see there is two basic problems with modern diesels

1 Complexity which will always bring potential problems

2 Emission controls which are Exhaust gas recycling which is a damn silly idea where you on purpose pump crap into the inlet side of the engine which is a damn silly idea. Then there is the new kid on the block the particulate filter. Which is a fine filter in the exhaust which is there to trap small lumps of soot and then once it gets hoty enough it trys to burn it off. both of these things are open invitations for mechanical problems

TheCarpetCleaner said:

Rover = guaranteed HGF.

6 years with a caterham 7 ragging it silly not one single single of failure

[mat205125]

thinfourth2 said:

2 Emission controls which are Exhaust gas recycling which is a damn silly idea where you on purpose pump crap into the inlet side of the engine which is a damn silly idea. Then there is the new kid on the block the particulate filter. Which is a fine filter in the exhaust which is there to trap small lumps of soot and then once it gets hoty enough it trys to burn it off. both of these things are open invitations for mechanical problems

Neither help economy either

[emicen]

thinfourth2 said:

TheCarpetCleaner said:

Rover = guaranteed HGF.

6 years with a caterham 7 ragging it silly not one single single of failure

Standard Rover HG in place or metal dowels and multilayer metal gasket?

[TheCarpetCleaner]

emicen said:

thinfourth2 said:

TheCarpetCleaner said:

Rover = guaranteed HGF.

6 years with a caterham 7 ragging it silly not one single single of failure

Standard Rover HG in place or metal dowels and multilayer metal gasket?

Exactly, I am sure the replacement / modified HG is fine, the original head gasket was gash.

[Ranger 6]

5 pages and no one has mentioned BMW swirl flaps?

115 pages of discussion and 50+ failures....
http://www.bmwland.co.uk/talker/viewtopic.php?t=53...

[Maty]

I've been driving an Astra SH for the past 2.5 years (just hit 45,000 miles), it's the 1.9 CDTi 150bhp version.

Had my first issue with the engine a few weeks ago, basically loads of black smoke when the turbo was winding up, very sluggish and finally going into limp home mode then clearing itself but still with plenty of black smoke.

Quick read on the astra forums and all blame pointed to the EGR valve being clogged up, I removed it and gave it a good clean out myself. Result being it now felt like a new car, loads more grunt, in fact I had not realised just how slow it had become over time.

I must admit I had no idea what an EGR valve was, but reading up on it it seemed very strange that they would recirculate gases back into the engine, gases that were basically deemed waste hence why they are passed out through the exhaust!

[mat205125]

Maty said:

I must admit I had no idea what an EGR valve was, but reading up on it it seemed very strange that they would recirculate gases back into the engine, gases that were basically deemed waste hence why they are passed out through the exhaust!

When a mechanic mate first told me what one was, and what it did, it took him quite a while to convince me that he wasn't talking complete "exhaust gas"

[The Wookie]

TheCarpetCleaner said:

emicen said:

thinfourth2 said:

TheCarpetCleaner said:

Rover = guaranteed HGF.

6 years with a caterham 7 ragging it silly not one single single of failure

Standard Rover HG in place or metal dowels and multilayer metal gasket?

Exactly, I am sure the replacement / modified HG is fine, the original head gasket was gash.

In my time Caterham racing I must have been exposed to over a hundred different 1.6 K-Series racing cars, all thrashed within an inch of their lives with varying levels of maintenance, and the only HGF failures I heard of were drivers who popped their rads during contact and carried on driving it until it conked out.

Any engine rebuilds were done with normal headgaskets as a matter of course as far as I'm aware, don't think any upgrades were allowed in the regs.

Undoubtedly certain configurations of the K-series have problems, but one should always be careful when making judgements based purely on personal experience.

[The Wookie]

Maty said:

I must admit I had no idea what an EGR valve was, but reading up on it it seemed very strange that they would recirculate gases back into the engine, gases that were basically deemed waste hence why they are passed out through the exhaust!

It's to do with emissions, particularly NOx

[HellDiver]

Ranger 6 said:

5 pages and no one has mentioned BMW swirl flaps?

115 pages of discussion and 50+ failures....
http://www.bmwland.co.uk/talker/viewtopic.php?t=53...

Same failure mode as the Vauxhall/Fiat engine I was discussing. Inlet manifold swirl flaps clog up and jam open or closed.

[Martin Keene]

mat205125 said:

thinfourth2 said:

2 Emission controls which are Exhaust gas recycling which is a damn silly idea where you on purpose pump crap into the inlet side of the engine which is a damn silly idea. Then there is the new kid on the block the particulate filter. Which is a fine filter in the exhaust which is there to trap small lumps of soot and then once it gets hoty enough it trys to burn it off. both of these things are open invitations for mechanical problems

Neither help economy either

Very much so. DPF's are going to open up a whole world of pain later in life. A petrol catalyst is a through flow design and cleans by a chemical reaction as the gasses pass by it and only gives major issues when the substrate breaks down.

Diesel DPF's are literally a fine wall that the exhaust gas has to go through to remove the fine particulate. Like putting an air filter in your exhaust, if you don't drive as directed, it will have to have an ash service, where the DPF is opened and cleaned of soot and ash. This assume cars DPF's will be servicable, and not just chuck them away.

The core of a diesel engine (block, head, crank, rods, pistons, cams, etc) is inherently more reliable than a petrol engine because it is burning oil and therefore the engines oil supply doesn't get diluted with fuel. Where as in a petrol engine there will always be some leakage past the piston rings allowing the oil to become diluted with petrol reducing its lubrication properties. We are only talking tiny ammounts of petrol and tiny reductions in lubrication properties, if you stick to the service intervals and use quality oil then both diesels and petrols should have a similar core engine life.

The big, and it is a very big problem, with modern diesels is mis-fueling. You can't put diesel in a petrol becase the nozzle is too big. If you did, it is unlikely you'd do much damage, it would smoke like Clarkson and if you ran it for long enough, it might screw up the Cat, but other than that it sould be okay.

Put petrol in a diesel on the other hand and your in a world of pain... The fuel pump and fuel injectors, are not lubricated by the engines oil supply they are lubricated by the fuel and petrol has very little, if any, lubricating properties. So if you fill a diesel with petrol the fuel pump and injectors are running without lubrication. Whilst it might appear you have got away with it, it will have shortened the life expectancy of the pump and injectors. How much depends on how far it has been driven.

For me, I'd only have a diesel if I was doing intergallactic mileages, buying a brand new one so there is no chance of mis-fuelling or it was a company car, i.e. somebody else problem...

[RobCrezz]

havoc said:

flakeypaul said:

Can you please now tell me that Renaults don't break, ever. Especially the diesels

A modern CR TDi is a fair bit more complex than an n/a petrol, and the components are under more pressure and more stress. So I'd be very surprised if they last as long, or are as reliable. Finally, direct injection has been seen on the VAG FSi engines to coke-up the inlet tract and the back of valves a lot quicker. I'd expect the same in a diesel.

But the comment above about maintenance is also very important - and as someone said on a different thread, a lot of people now treat cars like white goods.

Personally I wouldn't get a modern TDi unless:-
- I did very big mileage; and
- I got a decent a/market warranty to cover the big stuff
...but they're still the best answer for 20k+ mileages.

I don't think the direct injection coking up is an issue on engines with forced induction, but I could be wrong.

[Johnnytheboy]

We have an Isuzu luton van at work which has a lengthy warning notice on the door about what to do if the DPF warning light comes on.

IIRC it involves parking up and doing something else (can't remember what, probably idling?).

AFAIK this has happened once so far.